EPIDEMIOLOGY AND MANAGEMENT OF BEAN RUST IN E1IDOPIA

A set o/four publications

Reprints Series, No. 16

,

No. 16a.

No. 16b.

No. 16c.

No. 16d.

CONTENTS

Epidemiology and Management of Bean Rust in Ethiopia

Reprints Series, No. 16

A survey of cropping practiees and foliar diseases of common beans in Ethiopia. A. Habtu, L Sache and J.C. Zadoks. Crop Protection 15(2):179-186. 1996.

Crop growth, disease and yield components of rusted Phaseolus beans in Ethiopia. A. Habtu and le. Zadoks. 1. Phytopathology 143, 391-401. 1995.

Focus expansion of bean rust in cultivar mixtures. Habtu Assefa, F. van den Bosch and lC. Zadoks. Plant Patholog} 44, 503-509. 1995.

Components of partial resistance in phaseolus beans against an Etbiopian isolate ofbean rusto A. Habtu and le. Zadoks. Euphytica 83:95-102. 1995.

Nos. 16a and 16c are publíshers' reprints. No. 16b ís reproduced by kind pennissíon ofBlackwell Wissenschaft. No. 16d is reproduced by kind pennission ofKluwer Academic Publishers.

026 J -2194(95)00 121-2 Cmp (""I(''''h'l1 Vv! ;5. N<l 2 p¡:. 179-iM. !996

L('pynghl © lil()1i Ebc~wr Snence Ud ?nlíe;; m Gff'd~ Bn;¡¡¡n Al! nghh re:.erved

j)2ó!-214Jr;}tc $1;; (X) + ¡¡ (Iíl

ELSEVIER

Cm

A survey of cropping practices and foliar diseases of common beans in Ethiopia A. Habtu:' Ivan Sache' and J.C. Zadoks·§ "Department 01 Phytopathology. Wageningen Agricultural University, P.O. Box 8025, 6700 EE Wageningen, The Nelherlands, and 'Labora/aire de Pathologíe Végé/ale (INRA), Centre de Grígnon, F- 78850 Thíverval-Grignon. France

Field survcys werc conducted in three major bean growing areas of Ethiopia. Data coltected induded cropping systcrns and sc\'critícs of bcan diseascs. 'Ve used correspondcncé analysis fo charactcrize diffcrcnces in diseasc scvcrity bctwcen regiom. ánd seasons, and to determine associations betwecn gcographic arcas and croppíng systems. arcas and discascs, and croppíng systems and discascs, ehi· squarc analyscs suggcstcd a high probability of high plant dcnsity. high weedincss. high bacterial blight and high anthracnose bcing assodatcd with area 1 (Rift Valiey). In aTea 2 (Sídamo) there was a high probability of high rust intcns.ity, low plant density and low weediness, Arca 3 (Kcffa) was characterlzed by a high probability of angular and floury Icaf spots. 1n area 1 (Rift Valley). Iow rust intensity was closc)y associatcd wirh year 1 (1990) and high rust intensity with ycar 4 (1993). Anthracnose and bacteria1 blight showcd no dcar association with years, Sorne Jinkagcs bctween cropping systems and disease sc-vcrities 'Wcrc indicated. In arcas 1 and 2, there was a high probability of low rusr al early sowing and a high probability of bacterial blight al high wcedincss and hígh plant dcnsity situations. The probabi1HY of oDserving high rust ;;¡everity at high \Vccdiness was lüw. This study suggests that specific needs of areas, with thcir own productiún situations. must be considered in rhe process of developing stratcgíes for the improvcmcr'lt of productíon anu erop protcction in bc~ns.

Keywords: correspondenee analysis; rusl; anlhracnose; bacteriat blight; angular leal spot; floury leal spo!; sowing date; plan! density; weediness

In Ethiopia, common bean (Phaseotu'\ I'utgaris L.) is grown in rotatioll with cereals (¡mm. 1985). They are grown for the export market and as a food legume in par!s 01 the country (lAR, 1991). Cümmon bean, are gro",n from sea level lo about 2800 m (Schwarlz and Galvez. 1980). Under Elhiopian condilíons beans are wel! adapled 10 altitude ranges between 12110 m and 2(XXI m, and t<J r"infall conditions (Ohlander. 1980). Common bean is grown in most parts of Ethiopia, but production ¡s concentrated mainly in the east (Harerghe highlands), tne soutn and the south wesl (Sidamo), the w~st (Keffa and Wollcga) and in the Rifl Valle)'. Thi, gcographical range is associaled with a widc range of bean cultivars and diseases (Bos, 1974; HablU. 1987; (),Bannon. 1975; Westpha!. 1974).

Common be"n prodllction was abollt IOO.OOll ha in 1990 (eSA. 199211, b). Farm sueve)'s conducled in the major bean production regioos suggested no area al leasl twice Ihe official figures (lAR, 1991). The natíonal average for Mean ylcld is lovv. c. 6()(,,-700 kg ha-¡ and diseases are a major factor in reducing yields. 01 the more than Sil fllnga!' bacteria!. viral. and nematodc discases reported to occur on

§Author to whom correspondencé should be addressed. tpermanent address: Institute 01 Agricultura! Research, Nazareth Research Centre. P.O, Box 436, Nazareth, Ethíopia.

beans worldwide (Schwartz and Galvez. 1980; Allen, 198.'), few were rccorded in Ethiopia (Slewart and Dagnatchew. 1967). These older records gave litlle 'lttention lo geographic distrihution and economic significance. Recently. ao attempt was made to deter~ mine the occurrcn(.'c and importance of diseases of beans at various research andíor experiment staüons (Hablu, 1987), Discase epidemiology under farme,,' conditions is nearly unkno\Vn

Survey data can help to describe the geographical distribution of diseases, their relative importance and thell' epidcmiology (James. 1969; King, 1972; Savary. 19R7; Zadoks. 1961. 1966). Henee. a survey 01' bean diseases was lnítiated to investigate the intensity of hcan diseases, theír r-elative ímportance in several geographical areas. :.tnd their association with bean productíon practiccs (sov.-ing: data. growth condítion. planl dcnsity. weediness, etc.) in Elhiopia.

Materíals and methods

Sample regions

The ;...urvc.\ s were conductcd in three uf the four major ocall-growing areas nf Ethiopia: the cenlral Rift-valley (Easl and SOllth Shoa). sOUlh and southwest (Sidamo). and west (Keffa). Arens visiled and Ihe survey roule is

erap Prolecl¡on 1996 Volume 15 Number 2 179

A survey 01 cropping praclíces and diseases: A. Hablu el al.

g ,2000

m 1800·2000

1500·1800

1@1950.,500 111 ~ 450·950

1150.450

e· '50

• Prcvir.ce capital - - Province bO'Jndary --- Survey route

o 100 200 km

1974

Imp. Eth. Mapping & Geogr. Ins1. 1962

34' 3S' 40' 42' 44'

Map of average annual ralnta!! of

ETHIOPIA

8"

6'

40' 42'

FIgure 1. Map 01 Ethiopia show!ng average annual rmnfall, representatlve locatlons a'1d bean survey mute. From WestphaJ (1974)

,hown in Figure l. Area 1, lhe central Rin.valley (ARI), represents the hot, dry and erratie rainfall elimate where normally one bean erop is grown each year. Area 2, the soulh and south wcsl (AR2), rcprc,-:.,cnts a major bean growing area where beans are planted at lea~t twice ayear either as an intcrcrop or a monocrop. Area 3, ¡he wesl (AR3), is characterized by production of heans in intercropping systems with cither maize or ~orghum. Bere neans arc normally grown once in a yeuL

In the central Rif! Valley. the ,urvey was conducted ror four consecutive year, (l99(~1993) and information was gathered from 129 (icld," fn Sidamo. the survcy was conducted in 19911 and 1993 and data were collected from 80 fields. In Keffa, data wcrc collecled in 1(91). 1992 and 1993 from 53 fiel(h, In 10lal. 262 fields were visited.

Sample lields

Fidds were ordinarily selcctcd at intcrvals of 5~1O km

180 Crop Prolecllon 1996 Volume 15 Number 2

along the muin roads. \Vhen ncccssary, thc samplc sizc (Ihe number of observed fields per region) and lhe distaocc bctween samplc uníts (the arbitrarily se!ectró single plants) per field were adjustcd to ,uil erop distribution and field size. respeelively. AII s;rnplc ficlds helnnged to :-.mall, privatc farll1crs. Each field wa~ vi:-..ited once.

Sample unils

Of each .,:ample ficld, a g(.>neral ¡mpres~¡on of the fidd was ohtaincd a:-. to :..i7\':. shapc and crop \.:ondüion. Plants samplt.::d wcr.;: sy'tcmattcally se!cctcd hy m~lk¡ng a ~pccificd numbcr of equally :-,paccd pacc~ foJlowing <In invcrted 'Y' pattcrn. '(aving madt' Ihe prc-sl'l numher ofpaces (according lO the size "fthe ficld). the ncarest plant lo lhe righ! f(lo! was sampled. For caeh ficld. 10 plants were sarnpled for dise¡lsc assc<.;smcnt. A suh­~all1pk of thrcc trifoliolatc !caves pcr plan! was selccted from the uppcr, middlc ano ¡ower canopy layen. of thc matn stcm, yiclding ~t total uf 30 lenes pcr

ficld. Means of canopy layers were detcrmined per plant and ¡hen averaged per field for data analysis.

Crop and disease assessment

Each field was represented by a set of variables (Table 1) indieating field characteristics, crap developmental stage and dísease severíty for each of the follo\Ving díseases, angular Ieaf spOI (Phaeoisariopsis griseo/a (Sace.) Ferraris), bean anthracnose (Collelolrichum lindemulhianum (Sacc. and Magn.) Bri. and Cav.). bean rust (Uromyces appendiculalus (Pers.) Cng. (U. phaseoli (Pers.) Wínt.), eommon bacterial blighl

T able 1. Categorization of vanables used in correspondence ana!yses tor a $urvey 01 cropping practices and bean diseases in three geographical regions of Ethiopia (l. central; n, south: and 111. west)

Classe:-. ;-"¡umber oí' fields'" Variahk l boundaríc~) T JI 111

Arca (AR) ARI (('entral) 129 129 85 AR2 (south) RO BO 80 AR:; (wesO 53 ,7 ,7

Total 262 2·ttJ 2(12

Piant dcnsity (PD) PDl (1-20)' xn PD2 (21-4í)) .IR PDJ: (41 and abon:) lB

Tola! 202

S()wing dale (SD) SDI (early) -lR SD2 (opílmum) 130 SD;\ (late) 6H

Total 2-ló

Wccdines.\ (WD) WDl (Iighl) 103 101 WD2 (moul,Orutc) 105 7R WDJ (high) 3R o' -.'

Total 246 202

Discase<; Angular (AL) ALU (nhs.enl) 196 kaf<;pot AL 1 (prc),cnt) M

Total 262

Bact;::ri;!I hlight (BB) BB 1 (0.-·-2)' 124 112 106 Be:! (2-5) 50 46 .,7 BB3 (5 anÓ aboye} RB RH Si)

To!¡¡! 262 246 202

B{'an ¡BA) BAl (0-2) 140 129 lO." anlbr¡Kno),( BA2 (2--5) 66 61 5J

BA3 (5 ,\fid .. hove) 56 :'ir. 44 Total 2h2 246 202

Bc,an rust {SR) SR) «/-2) 1H6 95 71 BRl (2-5) In "2 ,I{()

BR3 (5 anu .\oo\'e) ,9 51} 51 Total 262 246 :;0:;

Floury I.FLl FLO (ao\cnt) ::24 !e,lf \POI FL I (rré~cnl) 4X

Totai 262

'Thn:e iln;tly\l.::~ .... erl· pcrft1flnl'd duc lO ImhLlIlec l11 ~dmp[¡: fI::kk 1. ,tll 'dnlrk hdd~ wo.:rc 1w:lmlcd in lhe ,1Il,dy~I~. IL ditla mi'~ll1g im "'''II\)! ,hile and Wl'Clhlh.'~~ Hl ¡In:a J (I\TV). IH. d,lla 111I~"1I1!! wr plan! dcrmty H\ ,1ft';[ I (AR [) ·PD. rmmhl'r nf rtilllh m', SD2, oplrmurn >'OWlI1j!. dllh: :I~ p.:n:cf\'cd b) filfmer~, u~uall~ 1.1(<.' Jun,,· \u .:arlv Julv lo! n:ntruL mid lo latr luh· ror ",'ulh ¡mt! \\,:;.;{. :mythin!f h;,;lorc h nlll .. iden,J ':,ld\' .mJ alter Inle \VDi: wt'"cl~d ;¡¡

lt-'asl Hoce lUuJ ah-..;nt·l' üi \hlhk wccd~. WD:. wced:. pr,,'\l'IlÍ huI OO! ¡¡; a ;,tmn¡! cnmp..'t¡hllll \ViiI> h(;\I1 .. ; Wfn. hl',m Íldd no! \wnkd ,11 ,di ano wenJ Infól.\liufl f,rciH" .. r thtlll !O fll :

'DI!>.\.·'I\I,' M,'Vt'fll~ tPf('p .. :.'rlmn ,ti h;,1I arca mkctcd m ""J

A survey 01 cropping practices and diseases: A. Habtu el al.

(Xant/¡omonas campeslrls pv. phaseoli (Erw. Smith) Dowson) and floury lear spot (Mycovellosiella phaseoli (Drummond) Deighton) Disease severily was defined as lhe affeeled leaf area, including the lesion and assoeíated chlorosis (Le. lhe non-greco area) as a percentage of lotalleaf area. Most data were collected around the pod filling stage (Fernandez el al., 1986) at a time when diseases \Vere conspicuous at all canopy layers.

Data categorizalion

Calegorizalion (here Ihe allacalian of seventles, recarded on a conlinuous scale from O 10 lOO, 10 a few distinct e1asses) is the transformation of quantitative dala into coded, qualitative dala. Class boundaries were chosen so lhat classes contained approximately equal totals (Table 1), (1-2%, 2-5% and >5% severíty. Thus, bean rust severilies were coded as BR 1, BR2 and BR3. Three sowíng dates (SDI-SD3), lhree weed intensities (WDI-WD3), three planl densities (PDI­PD3), Ihree areas (ARI-AR3) and 4 years (YI-Y4) \Vere considered.

Conlingency tables

AII variables were encodcd to build canlingency lables (Table 2), to represent the bivariate distribulion of fields according to lwa classifications (e.g. sowing date and bean rusl severity). An cntry in a ceJl oC a contingency lable represents the number of ficlds fallíng inlo that cell. The independence or Ihe frequeney dislribulions of lwo variables \Vas tested by chi-square analysis (X'). Several conlingency la bies were combined inlo a single matrix, e.g. wilh disease severities as columns and othcr variables as rows.

Correspondence analysis

Because of the non~normal distribution of most vari­ables and lheir low precision. a non-parametric method 10 analyse categorized information was used (Hill. 1974; Nutter el al .. 1991: Savary and Zadoks, 1992; Savary el al., 1993). Correspondcncc analysi, is a multivariate melhod that allows lhe piclorial repre­sentaríon of contingency tah1es in order to identlfy a$Sociations belween two groups of vanables. These lwo groups are rhe columns and lhe rows of Table 2. D¡sC:a~e severities in colurnns are variables to be explained while variables in lhc rows are explanatory variables, The variables were treated as either active (direcrly used in the analyses) or additional (proíected in lhe graph but nol used in ¡he anulyse,).

Corrcspondence analysis was t:onductcd for each bean growing arca and aeross all thrce geographical arcas to characterize associatíons between cropping systems and disease severitics. The method generated graphs which plolted categorícal variables 10 examine thcir relationships. The res-ulting graphs use a X} di!-.tance to reprcsent relationships among catcgorízed variables (Benzécri. 1973: Greenacre. 1984: Savarv el ,,/.. 1993). The inlerpretation 01 the graphs is based on the strcngrh of .he assodation accounted for bv the ilxes, the classes that contribute most lo each of lhem. the proxímity of points representing dasscs. and the

Crop Protection 1996 Volume 15 Number 2 181

A survey 01 cropping practices and diseases: A. Habtu et al.

Table 2. CantingencY,tables ter the ana!ysis of data frorrl four years (1990-1993) frorn a survey of three bean growing areas (central, so(..¡th and west Eth¡OplaJ ' ,

Area by disease BRI BR? SR3' BAl BA2 BA:' BB: HE2 SB} ALll ALI FU) FLI

ARl 55 42 32 5lJ 27 43 11 3:- HJ 12') (¡ 12V Ii AR2 Ll .j.2 25 53 15 12 70 x 2 61 19 kO " AR3 3d 13 2 2B 24 1 41 7 .1 n 47 ,

~!'\

Year b} dlsease" BRI BR2 BR3 BAI BA2 HA3- BBI 13132 llB)

Yl 24 13 7 23 9 12 6 4 29 Y2. 14 9 7 10 (, 14 2 " 22 Y3 12 9 .¡ 9 n llJ H 16 Y4 5 11 14 17 ti 7 2 12 16

Cropping s~ stem by diSéa5e BRI SR:;: BR' SAl BA2 BA3 BHI HH2 BB.1

SDI 28 :3 7 23 22 14 23 7 29 SDl 4n SI }9 61 29 31 59 23 :w SD3 27 2S 13 45 10 I1 30 16 20

BRI BR2 SR3 HAI BA2 HA:' BHl llB2 !lB} \\DI .1n 42 25 ó6 30 19 81 ¡t) 15 WD2 :1,7 3H 30 47 2L 13 25 19 ,"0 WD3 22. 12 4 16 7 14 1> 8 23

BRI BR2- BR3 HAI BA2 BA} HHI BB2 Bm PDI .11 .12 23 39 18 " óO } Il PD2 10 10 , 33 17 8: :'7 12 9 PO} 311 2~ 20 J?i I~ 30 " 12 ~n

Ar~a by aopping S)'stéffi PDI PD2 PD3 WDI WD2 WD.1

ARI 11 g 77 22 4(, :7 AR2 52 2K lJ 57 IV -1 4R.1 .14 2 1 22 i.3 2

r"r ,k"U'IP11(\(l 01 ';Hl;¡hlc' rdcr 1,lt-,k I D<I\,I Iruln ¡,r':d ¡ pnl~

Table 3. Geographical d·strlbt.,;t:on and dlsease severity (% measured as proportion of leaf area infectad) of bean d¡seases in Etrlopia ('9901993)

An.:a 'foca! BR HA

I \NO :2 " 14 !Wl 30 hJl IW1 22 -1 ,~

191)3 S.I 1.'1

\kan .1 1 4 . .1

!Sl90 )).; O. íJ 191)5 ,1.1 2.2

Ml-,Ui 4.1 l.ú

I 'Ni) I 3 2.2 lt¡tf2 211 2.4 lW3 2,9 .l7

Mc,m 2 1 2,7

paths representing a !\uccessl0n of c1asses. Similarities in pattern or direction of paths indicatc correspondences tha! can be lested further usíng the appropríate X' lests (Savary el al .• 1993). Analyscs of data \Vere performcd wilh Ihe NDMS computer programme (Savary el al .. 1988).

Results

A summary of the diseusc survey data o\'er a 4 year

182 Crop Protecl(on 1996 Volume 15 Number 2

D1C,'"'I'.;(C 'éh'nty ('\';,1

BB AL H DI

" 1 n,O IJ () íI \)

so 0\1 {)Ji .' I nO (jJI tUi 3 " .;,~ 0\1 0.0 2,0 65 ¡)JI (¡I) 2 4

0:-; 1 , i!O 1 , l.íI !U 00 ' ' 0'1 O; !lO 1 '}

(j 1 :: " ¡.J 33 4n 1..2 0,5

.' 1 lB ~ K2 Oll ' , 5.k ,Li 0,2

pcríod (Table 3) ifHlicate\ vanation m dí"ease scvcrity wíth years and geographical areas, ncan rust (BR), aOlhracnosc (BA) ¡¡nti baelcríal bhght ([lB) wcre more wídely díslríbulcd ¡han angular ¡eal spol (AL) or floury leaf spol (FL) which were no! found in "onu', rcg¡ün~. In farmef",< fic1ds. disea:-.e severity \Va .... general and mean severltv did not exeerd 71}'o.

Anaiysi~ 01' the data with corn.;~pondt.'ncl' <Halysi:-. suggCqS associations of years, arcas ano cropping practiccs with henn di;-,eascs, The ax('s gcncrah:d by corn.:spondcl1cc analjscs ;J(.:(.:ountcd ror >i)O(~,;, ef the

;;g Q

~ N , '" ~

05 AR3 •

POl

O

-0.5

·10

+

WDl ... AR2.

P02 +

-115

WD2 ..

WD3 ARl PD3 .... +

• maiAR)

o 0.5 1.0

Axis-1 (92%)

I

1 5

Figure 2. Ordination of six variables by correspondence analysls. The variables, all active, are area (AR1 .. AR3), plant density ,PDLPD31, and weediness IWDLWD3), n = 202. The graph is largely dominated by aXIs 1 (horizontal, i. = 0.92). AxIs Z (vertical, t 0.08) nicely separates areas but has little explanatory value

total inerHa (technicalterm of correspondence analysis approximately equivalent lo variance). These axes were used lo draw graphs and inlerprel resulls.

Area and cultural practices

Figure 2 ís produced w!lh area. plant densíty and weedmess as active variahles. Most inertia i5 explained by axis 1, roughly representlng ¡ncreases in plant deosíty aod weedíness, Tne graph sbows clear a>socia· tíons belween area I (Rifl Valley). high planl densíly and medium lo l1igh weedíness. Arca 2 (Sídamo) is aSl\ociated with low weedjness and low to medíum plant dénsitiés, area 3 (Kcffa) wíth low planl densit;es.

The~e ¿lssociations are confirmed by X:: tests on tWOm

dimensional contingency lables. High plan! density has a hígh probabilíty in area l. medium pillnt densíty in a!ca 2. and low pl¡mt density ln arcas 2 and 3, (n = 202. X" = 188. df 4. P« O.OOl). Low weediness has a low probability io arca I (Ríft Valley) and a high probabili!y in area 2 (Sídamo). Arca I has a high probabilíty of medium and bigh weedincss (n = 246, '1.=

37. df = 4, P « IUIOI), Plaol density and weediness were "Iso slrongly a"ociated (n = 202. X' = 34. df 4, P« (UXlI),

Year effects

Thc correspondence Hnalysis of year effects on the major diseases, rusto anthracnosc and hacteria! blight is shown in Figure 3, in which all variables mentioned are active, 'rhe two axes represent 94 tyo of total inertia. The horizontal axis is largely determined by rusl and baclerial blight. The paths of rust and anlhracno", cross at nearly right anglel'\~ índicating independence. The path fmm medium 10 high bacterial blíghl runs opposite lo Ihal 01' rusl. Ycar 4 (1993) is associated wilb high and year 1 (1990) with low bean rusl (n = 129. X'

15, df 6. P (UI2). Years 2 and 3 (1991. 1992) were intermediale betwcen years I and 4. No signílicant assodations were found helween years ¡lnd anthrac-

A survey af cropping practices and diseases: A. Habtu et al.

nose, lhough Figure 3 sccms !o suggest an assacíation he!ween years 2 and 3 and high anthracnose,

Cultural practices and díseases

In Figure 4. the firs! axis largely represen!s the trajeclories of bacterial blight, weediness and anthracnose. The second axis largely represen!, the lower par! of lhe plam density trajectory and

e RU'llí8R¡

V Ñllllta/:'!\OQ (6A)

• v_m 0.5.---==========-----. 881

~O.25 i\:¡

<>. ••• , ••

". ~~~ 6A1

~1 ____ ¡¡ !~\... Y4.

~ N

"' ~ """ .. FJf2 BR2 ", .: BB30 ..... ~~'O.~,,!'."::_~- .... -. d Y2_..1 BB2 BR3 ¡Y3

o

BA3\.' I .o .25+----.--'::;"-"-,--,--.-...,..-,-..... ---l -OA -0.3 -0.2 -0.1 O 0.1 0,2 0,3 0.4 0.5

Axis-1 (71%)

FIgure 3. Ordinahon of tour variables by correspondence analysis. The active variables are years (Y1 "Y4), and three major bean diseases, rusl (BR1..BR3), anthraGnose (BAl "BA3) and bacterial blight (8B1 .. 883). Total number of fields, n = 129

¡ .. o Rus! (BA)

o COI1lmOl"l b~elttlal bhlflt (se)

'V Alllll'iKOO!ie (BA)

+ PIa~1 domsJty ¡PO)

I • Wued'nflU (WO)

T----~~==·=····=~=·=~:~='=·(=":(====~------_, 0.3

0.2

P02 +

0.1

982 WD1 .~8 .. ~~ ..... _ .. ~ .. ~~

88~ ............. 17~-"""" SD1·· •••• W03 ~ BA1 SD3 --........... ~. b O V ..

BR2 BRl BA3 +BB3

<)1-0.1

'" ~.02

-0.3

+ POl

· 0""0 P03 • SD2 ...

" WD2 , , • • t

BR30

-o .• +----r---r--,---.-~-.-~__J -0.6 -0.4 -0.2 O 0.2 0.4 0.6

Axís-1 (75%) Figure 4. Ordination of six variables by cOtTespondence analySIS, The three majar diseases (rust. anthmcnose and bacteria! bnght are relatad to three variables representing culturaf practices (sowlng date. weed¡ness, plant dens¡ty). AiJ six variables are actIVe. Total number of fields. n = 202

Crop Protection 1996 Volume 15 Number 2 183

A survey 01 cropping practices and diseases: A. Habtu el al.

Ihe upper part of ¡he rust Irajectory. whích run in opposile directions. The third axis (A = O.OJ) is largely dominated by Ihe sowing date Irajectory, paralleled by Ihe lower parts of Ihe rust and anlhraenose trajectones, Ihe Jatter running in opposite direclÍons.

In Figure 4, the rus! alld plan! densily trajectories run "early paralleJ. Early sowing is associated with high values of weediness, bacterial blight and anthracnose. Low plan! density (PDI) may be associated wilh high severities of rus!. Early sowing is associated with low rus! severilies and intermediate sowing dates with intermediated to high rusl values and low weediness (Figure 4). A low plant densily is strongly assodated with low weediness and low bacterial blight. High weediness and high plant densities are associated with high severilies of bacterial blight and anthracnose.

Sowing date had a clear effeel on disease severity. Early sowing was associaled with low bean rust whereas normal sowmg date was associated with high rust severity (Figure 4). Normal and late sowing were associated with intermedia!e and fewer high bean rust intensities (n = 246, X' = 13. df = 4. P = 0.011). Early sowing was associated to sorne degree with intermediate anthracnose levels. Lare sowing showed the inverse patteen. Normal sowing was rather neutral with sorne excess of high anthracnose levels (n = 246. X2 = 13, df = 4, P = 0.11). Bacterial blight showed no significan! assoeiations with sowing date.

High weediness was assodaled with a higher prob­ability of low bean rust levels whereas low and medium \Veediness were assoeiated with medium and high rust levels, respectively (ti = 246, X2 = 9, df = 4. P = 0.(7). Low weediness was highly associated with low bacterial blight, whereas medium and high weediness were strongly assocíated wilh high hacterial blight (ti = 246, X' = 62, df = 4, P « 0,(01). Intermediate bacterial blight was neutral as to weediness. The association between weediness and anthracnose waS not significant,

High plant densities "ere assocíated with high levels af anthracnose, low plant density with low levels of anthracnose (n = 202, X' = 19, df = 4. P« 0.(01). Similarly, high plant densíty was strongly associated with high bacterial blíght (n = 202. X2 = 111, df = 4, P « 0.(01). :-./0 significant assDeiation was found between plant deosity and beao rust severities, despite strong graphical associarion of high levels 01 rust with low plant densities.

Geographical areas and di~í'ases

The lwo axes generated by correspondence aoalysis accounted (or nearly 100% of lotal inenia. Arca 1 (Rift Valley) \Vas ciosely assocíated with high and inter­mediate levels <Jf baeterial blight and a high level of anthracnose (Figure 5). Area 2 (Sidamo) was closely associated with a low level of anthracnose and bacterial blight and intermediate to high level of rus!. Area 3 (Keffa) was assodated with a high presence of angular and f10ury leaf spot, low Ievel of rust and intermediate level af anthracnose.

Whereas the three bean rusl severíty categorles were rather evenly distributed over area 1 (Ríft Valley), low bean rust severity had a very high probabilíty in area 3 (Keffa) and a very low one in area 2 (Sidamo). Medium lO high bean rust severities had a high probability in

184 Crop Protection 1996 Volume 15 Number"

18 u

FU

1.2

ti Al1

& '" 06 , '"

AR3

•

, o

l7 A"'h,iW""C '3A'

e An~!IIM lila! ~po' ;"'l)

::. Fk>wyl""'!'r~,JL) --------._ ...... _-

SR1 BA2 e v f , ~

o SBl " BB2 i i) .... ,o- ... ----, ... - .... 0.---- ... 0 , SAl\!' AR1 8831

AR2. BR20"r 6. AÓO ~:-¡BA3 BA3

U FLO

-061:----~~----~~--~~~----~ ~1.0 -1).5 o 05 10

Axis-1 (77%) Figure 5. Ordinatio¡; 01 six variables by correspolldence analysis. The three aJeas (Ríft Valley, Sidamo and Keffa) are related to five bean dlseases (rust. antnracnos€, bacteria! blight, angular leaf SPO! and floury leaf spot). Areas, rust, anthracnose and bacterial blight were the active vanables whereas angular and floury lea1 spot wore additiúnal variables. Tota! number of fields, n = 262

area 2 (Sirtamo) and a low (lne in are a 3 (Keffa). The linkages were highly significant (n = 262. X' = 44, df 4, P« rUIOI).

High leve!&- of anthracno:-.c \.\-ere (lver-represented in area 1 (Rift Valley), low anthra"nose severilies in area 2 (Sidamo), and Ínterrnediate severitics in area 3 (Keffa). The ."oeiation was significant (n = 262, X' = 34. df = 4, P« O.tlOl).

Low levels of bacterial blighl were slfongly umler­represented in area I whereas medium ano high values \Vere under-represented in areas 2 and 3. High sevcrities of baclerial blight \Vere strongly over·represcnted in area 1 and uoder-represented in arca 2 (n = 262, X' = 161. df 4, P «O.nOl).

Angular leal SpOI showeú a very high probability of low values in area 1 (Rift Valle}') and of high values in are. 3 (Keffa). whereas area 2 (Sidamo) was about average (n = 262, X' = 157. df = 2, P« n'(~)I).

High levels of floury leaf 'pot were strongly ovcr­represented in area 3 (Keffa) and under-represcnted in area 2 (Sidamo) and especially in area 1 (Rift Valley) (11 = 262, X' = 232, df = 2, P = «OJWJI). .

Discussion

Information on the geagraphlcal di,trihution of p:ant diseases is uscful to understand the nccurrcncc of disease in a ncw area and to Set priorltics for discase managemenL Thc understanding can he incrcased (Weltzien, 1972) by dístinguishing degrccs of intensíty of the disease within toe arca nf its occurrcnce. distinguishing subareas witn high scvcrity and marginal occurrence. and as an aid to explainíng the assoclations bctween cropping system:-; anu disc;.¡sc intensiHes, Hablu (19H7) considered the presel1ce or absence of diseases within a given area of Ethiopia, describing diseasc severities at experiment statinn;;" The present Mudy rcvealed the widc prcvalence of sorne bcan dhease .. , the límitcd occurrcnce uf others and the association nf d¡~ease inteositíes with cropping syslem~"

Croppíng practices

The prevalence and severity of bean diseases vary with cropping practices. A general trend concerning the a"odalion of cropping practices and disease severilies was {aund using correspondence analysis. In are as I and 2, low rust was associated will¡ bolh early sowing and high weediness ",hile high Ievel, of rust were assodaled with intermediate sowing dates. The low severily of rust al early sowing dates may be due to several faclors. First, early sowing dates might have led to lhe escape ol crops from rust inoculum arriving late. Secand, early in the cropping season, temperatures near Ihe canopy may be sliII high and rainfull low resulting in long periads with Hltle leal wetnes,. Leal wetness is an important lactor for rust infection (Harter el al., 1935; Imhoff el al., 19111).

Hígh severilie, of anthracnose and bacterial blight were assoclated with intermediate sowing dales. Early sowing and moderate weed densÍ1y both favoured anthraerrose and bacterial blight. In area 2, anthracnose afid bacterial blight were nearly negligible during the survev periodo Here lhe beaa produclion praetice is characterized by light weeding, low plant density, good erap rotation, and possibly by the use of healthy seeds. The difference in weeding and plant density between areas 1 and 2 (Figure 2) was ohviom •.

Area and year

The roles of the environmenf and of human action in lhe development of plant diseases are depicted by the discase tetrahedron (Zadoks and Sehein, 1979). The prevalcnce and scverity of bean diseases in Ethiopia varied considerably with the envíronment, both by area and vcar. Within an area. disease ~everitíes were influ~need by cropping prnclÍces. Beans produced under cool conditions at inlcnncdiate lO high altitudes are oflen aflecled hy rust, anlhracnose and angular leaf spot. under hOI and dry conditions by bean comrnon mosak virus. eommon bacterial blíght and root rots, and undcr hol and moist c1imates by web blight (Allen, 1983).

The eenlral Rift Valley, area 1, is characterized hy high 'emperature and high varitltion in ratofall amount and intensity. Undcr such condittons, the common hcan diseasc:-. are bean cnmmon mosaic virus and common bacterial hlighL In out" stud}. cornmon bacterial hlight was most severe, hul rust and anthrac­nose wcrc ulso ohserved. In arca l. angular and f10ury leaf spots were practically a"sent. The south, area 2. is moler than the central Rift Valley, and has dependahlc mins. Here, rust was sevt:re ando surprisingJy. anthrac­nosc wa:-. ¡nsignificant. In the south, hcans were carefully wl"cdcd, pl¿¡nt dcnsiti\!s wece rather low. pcrhaps advcr¡.;dy influencing lhe microcnvironment required fOf the develnpment of anthracnose. In the wcst. afca J. the situalíon was rathcr cleaL 7vlany discases wert! prescnt hut the important nncs were angular and floury leal' spots. The w('sl is charac:terized by a hum id climate, high temperalurc and high ",infall.

Though such is the general trcmL discase sevcrity was affcctcd by ¡.;casonal variation. primarily rainúdl and tcmpcraturc (Savary, )9~7). in an . .'4I L whcll temperaturcs wcrc high itnd moi¡.;turc wa~ limiting.

A survey 01 cropping practices and diseases: A. Habtu el al,

common bacterial blight became dominant (Table 4, year 3). When there was a dependable rainfall resulting in a cooler temperature (year 2) anthraenose became the principal disease. Anthracnose became even more important when farmers used infected secd from Iheir last harvest. A high anthracnose season, as in 1991, resulted in crop damage. In arcas 2 and 3, the association of disease intensities with seasons is not very clear possibly due to the low variation of rainfall and temperatures between seasons in these two areas. lt is diffieuIt to find rainfall and temperature data to accuratelv describe these areas. Table 4 provides a general picture where data is provided for Nazareth (area 1), Awassa (area 2) and Jima (area 3).

Obviouslv, nol all bean diseases accur everywhere, at the samé intensity. Their prevalence and severity depend 011 area and season. Generally speaking, rust, common bacterial blight and anthracnose had a wider distribulion in Ethiopia than angular and floury leaf spol. Wor!dwide (Schwartz and Galvez, 1980) rust, anthracnose and angular leaf spot are reported to have wide distributions. Our results suggest priorities for strategies of control of angular and floury leaf spot in the west and rust in the south. In the central Rift Valley, where rus!' eommon bacterial blight and anthracnose oceur simultaneously. at different degrees, any control strategy designed to reduce the impacts of diseases must coneurrenlly deal with these three diseases,

Research implícations

The variation among environments. erops and cropping regimens brings abaut concomitant varialion in diseases and their intens;ties (Boudreau and Mundt, 1992: Zadoks and Sehein, 1979), Management of diseases requires an understanding of Ihese interrelated and interacting factors leading to epidemics.

The presen! s\Udy provided some clues to Ihe understanding of the geographical distribulion of bean discases, the association of disease intensitíes with ureas. seasonal variutíons of disease· intensities and the intcractions between cropping systems and disease inlensit;es. Understanding Ihe system will help to evcl1tually achieve an economicaHy sound and effident

Table 4. Weather data from sorne representativa !ocations s3rnpled for bean diseases in Ethiop¡a between 1990 and 1993

\\ ~'d¡h,,'r \;lliabk .. l,\'Icatln!1 19941 ! ~}I} I ó.

¡:bmfall' N,I/;¡r.;-¡h ~5LS 5'¡K3 ;\v,;¡V,J.j 37H.: :'09,(; JlIlla 12{1~.9 75': . .1

~l¡n h:ml'· . Sa/dl..:th 15 <.) 1:'.1 A\\ ,1'''H lJ.3 [3.-l-J 111M 1 ~ -l- I :.\l

Ma'\. (cmp Na/dr¡,;th 27 7 275) I\\\d"~;¡ :6.3 '::'.9 Jml.l 2-1- 7 25 -l-

j¡\ 1'1'11, d .• ld \\,'f(' ,\\,nl.,bk I,H \'!ll~ .j l!1\lIlth, R¡"II.dj {111m) d,Il,¡ lit:.:! ,,1 .;; ¡)j'\1lth" P .. hl~-S~Th;lHh<.:rl I '·¡\\l'd,HlH<.: I ( ) d,¡u .Ih·td~l',j "\:1 'i m"l11h ..

199~ ¡'N3

555.0 5~." ~ll,U ~55.7

t lSto.1 ll! tj.t-

I .. LX 15.-l-1:'.1'; 13.h I::!,-l L!.6

~(}.7 27.il ~5J\ 25.: 2,t7 :: .. b

Crop Protection 1996 Volume 15 Number 2 185

A survey 01 cropping practices and diseases: A. Habtu el al,

erop and bean diseases management strategy, The Ethiopian National Bean Improvement prograrnme is trying to betler foeus it, breeding aetivities by regional­ization, recognizing four majar bean growing areas with different ecologies (differences in altitude, rainfal!, temperalure, soiL production system, production constra;nts and objectives). The present findings confirm that the regionalízation of the breeding prograrnrne is well justified, 1'0 address lhe specifie needs of the difrerent regions, the programme should, perhaps, integrare breeding and crop protection activíties, in order 10 develop aD overall stralegy for lhe management of common beans,

Acknowledgements

The authors wish lo thank the management of Nazret Research Center for providing facilities, st3ff of the Ministry of Agriculture, Ziway and Meki Zone, ror arranging meetings with farmers and Abiye Tilahun and Belete for assisting during data colleetion, The researeh was funded by the Institute of Agri­cultural Researeh, Elhiopia, Wageningen Agricultural University, The Netherlands and the CIAT eastem Atrica regional office. \Ve thank Dr S. Savary for hi, critical comments on the draft of the manuscript and Piet Kostense lor his contribution in preparing the figures.

References

Allenj

D, J. (1983) The Patho{og.\ o[Tropical Foad Legumes: Disease ResisttJ.ncc in Cro{f lmpro¡,wnent. John W¡ley and Som:, Ncw York. 413 pp

Benúcrl, J. P. (1973) C<Jnalyse de.l" donnén". VoL!I Canaly\..: d..:~ correspondances. Dmiüd, Pati..,. 032 pp

Bos. L (1974) V/rUS diseases of puf-Jes and Olner erap" ím Elhiopill}. fAO working paper AGP:DP/ETH171!533. Rome

Boudreau, M, A. aoo Mundt, e, c. (1992) Mcchan¡~ms of ulteration m bcan rus! epióemiology duc 10 intercropping wilh maizc. Phyto­Pdlholngy 82, 1051-1(61)

eSA. Central Statíslfcál Authority (1992a) Agriculturc sample sun'ey 1989190: Results 00 arca, production and yicJd of major crop' by ..,cclor and sca,>OfL Statistíca! Bullctin 103. Addis Ababa, Ethiopia, 95 pp

eSA! Central Sbitisttcal Autltority {!tJ92b 1 Agriculture _'¡ample 5urPt'y

}Q9fJ:91: Results Oh arca. productior. 2nd yicld of major crops hy ;'I.'ctür and ~casún. Statistical Bullctin 104. AddlS Abaha, Eth¡Qpia, 30 pp

FernardN. F" Gepts, P. and l..opez. :\'1, (19~6} Eta.pes de Desarrollo de la planta de frijol comw, (Phasc-olm. vulgar¡.., L, elATo Cati, ColombIa, 34 pp

Greenac~, M. J. (1984) Tlu-'or) iJnd App!inuion oi CfJrrespondf:'n(Y Anll!ysi,s. Acadcmic Prcs$.. Lonuon

Habtu Assefá (1987) Haricot bcall dij,~ase,> and thClf lmportunce in Ethiopíu. Elhiopiun 1. Agrie. 5ci. 9. 55----66

186 Crop Protection 1996 Volume 15 Number 2

Hartcr, L. L.~ Andrus, C. F. and Zaunreyer, W. J. (1935) StUUlt'S oro beao fllst caused by Uromycc~ plwst'ofi lypira. J Agm. nes. 50.737-~9 .

Hm, M. O. (1974) Corresponderlec anahs¡~: a net!lectcd mult\\ariatc analy.sis. Appl, Sra!, 23, 340-354 . ~

lAR, Institute of Agricultural Resear('h {\41) 1) Rescareh (l1i Jlrlf/CO;

hean in Elhiopia: Proceeding!> uf a nationa! work<,hop hdd In Addl~ Ababa. Etbiopia. 1-3 Octobcr 191)0, 114 pp

hnhoff. M, W .. Maín, C. E. aud l.eonatd, K. J. (1981) Effcct of Icmpcraturc. dl.'w penod and agc of !cave,"" ~por.:'s, and sourcr pustuks 00 gcrm¡natwn of be"n rust un:dHl'iporcs Phyropafhology 71, 577-Sl'i3

Imr~> A. {:985) 8(!~n prudll.c(wn Ín Fthwpía, In Proce.eding /Jf (j

RegIonal Workshop In Polcntut! uf Fiel:.! Beans rpha"5Colu"S \ ulgar¡~ LJ In Wesl Asia ilml North Africa, Aleppo. Svrio. 21-23 !vía\-. 1983. CcntTO Internacional de AgricultuTi.l Tn;pH:.11 (CJAT). Cali. Colombia, pp. 1~38

James, W. C. (1969) A SUrH;) uf foliar d!\C;:I..¡c" of spring hiHln in England and Wales in 1%7, AIl:fl, /lppL Biol. 6.1. 253-26J '

King, J, E. (l':l72) Survc) of lodar dbI.'JI¡CS ül ,>pring barlc)' In Englanct and Walcs 1967-70 Pltmr Po/hu!, 21, 1:t-35

Nutter. F. W., Jr .• Teng, P. g" and Shokes; F. xl. (1991) Dí~ca~c a~\c~\mem (en11'> anJ conccpt>:, Plaw DH, 7S. ll~7-1188

O'Bannon. J. H. {1975) Nrmatode ,)'¡;n ey in F;hwpw. !n~fltute of AgriculturaJ Rcsc.4n:h, Addi" Ahaba. Elhlupla and FAO. Rome

Ohlander, L. J. R. (lYsn) Rcsearc/l un íWrtCo( hl'an producflim in l~(hiopi{/ /972-1976. SWCdl\h Univcr ... it\ of A~flcut{uraJ Seicnce .... Depmtrnenl of Plant Hu},bantlry, Reporl S2. l;rp ... ab_ 2SH pp

Savar)". S. {11J87} Enquétc ~ur Ic~ rr:<ll;¡dic,,- fongiquc\ de ra¡-achidc (.4radtís hypogat'({ L) en C6t.:.- {j'I\"OIn:. 1. \1éthodcs d\:nquétc dcS\:ript!\,c Les conunion& cu!llIru¡c~ l'1 hcs princ-ipalc" maladiu .. \ic¡hcri(/ful\ 1. Plam Patho!. 93. 167-1,s.s

Sa\'ary, S., Bose, J. P., Noirol. M. and Zadoks, J. C. (l%!'{J Pcanut rusT in WC\t Africa: a ncw cnmponcnt In a multiplc patho ... \:-tcm Plam DlS. 72. 1001-1009 .

Savary, S., Fabellar, N., Tiongco. E. R., and Teng, P. S. (1993) A charactcnLation 01" rice tungro epldt'mlc~ in ¡he PhiHppinc" from h¡~toril.'al \urvcy data. Plofll J)I.I. 77, 37ó--.s1

Savary, S. llnd Zadoks, J. ('. (19tJ2) Analysb ot cror lo,",,, 111 the mullipk: Pu!hú;,ystém gmundnut-Tus!-lu[c leat ~rOL 111. Corrc"pon­tiente am\ly~¡"'_ erOI' Prola 1, 11. 22~23L1

,"'ichWllrtl, H. F. and Galvez, G. E, (19XO) Benn produCfion prob{efl/s fh,eow!, peH, \oí!. ami dnnum consrrai;¡{<, of Pha\c(llus vl.Jlgar¡~

CfAT, ('alL Colomnl:::¡. 424 rr

Stt'wart, R. B. and Dagnatchi',,", Y. {1%7) Index of pÜUIl di.waH'-í in ElfúoPÜI, Ex¡x;rim"':n) St¡l\¡on Bu!lctin :'·<1 C(jllc&~~ 01 Agriculturc. Alemaya, Olfe D<lwa

Welukm. H. C. (1')72~ Geophytop.¡¡(Í"mlogy. Arm. Rel-. Phy!op.ltllOi 10, 277-2qH

Zadoks. J. C. (l%il Yellow fU\! 00 whcat. ~tudie" in cpidcml{llogy am.I phY:'lOlogtc -.pcdaIt7-iltion, T1Jdsrhr Plzft'kfe!1 67. 69---256

Zadoks. J. C. (19M) 00 the dangcrs of artificml mfcetmn wíth \cl!ow rus! to thc harte)' cmp 01 Ihe Ncthcrland\: A qU;:\ntll,l!ivc app'mach Nf?fherhmds J. Plut!{ Pmho{, 71. 12-19

Zadoks. J. C. and &;heín. R, C. (l979) E/JltJemialugr alU! P{mtf Di.\·t'(Hí' MaflI1Kf'ftl<'tIf OxtorJ Uni\.cr.,¡f! Prc..". 'le\\' York alld Odore 427 pp

Rcccivcd () Junc 19'H Rcvi'icd 24 Augu:.l t 'N5 Al\:Cpt<:U 3D Auguo.,t 191)5

J. Phytopathology 143. ~91-401 {l995¡ ( .. 1995 Blackwell \\'issenscbaft:--Vcrlag. BCrllll ISSN 0931-1785

Crop Growth, Disease and Yield Components of Rusíed Phaseolus Beans in Ethiopia

A HABTl: 1 Z and 1. C. ZAOOKS'

IDcp¡¡rtrnent of Ph~ topath{)iug:~. \Vageningen Agrí.:ultural Uni\t'r~H~. PO B~,\ XO:::::'. f¡ 700 EE Wngcnmgcn. The Netheriands: :Permanent address: lnSlnmc oi' Agncultural Re"earcn. '\azareth Re:-carch Centre. PO Bo:\ 4:\1). N'lzaretb. ElhlOpia

With 4 figures

Received Aprii 7.1994: accepted October 17. 1994

Abstr:u:t

Crop growth and dJSedSe ep¡demlC:" m :;pra~ed ¡.¡nd non~,>pr;!)ed hean pio!;,. ;Irtiticially infectec ",ilh rtbI (Urr!ll1l Cl'\ UflJiI'I¡,{¡ut!aw,j .~ \\eek" arter emergcncc. \\;;;re asseiscd \~eekl! in t\\ (1 \.'uhlvar:,.,. ,1: t\\O ]ocal1on" for 1\\'0 "ea~OIh Disease mtensH~ \\'dl> n.'í!ulated ~ [he applic,Hlo;¡, oC j fungiclde al 5 spra} frequenC!{~~, FunglCHle tlpplicauon mfluenccd leal' ¡¡rCa mdü (LAl) and reduced ru'>! mten:.ll) The fungJcide ndd no $lgmticam etfecI 00 Olhcr t.hse,!:ses ,Illd dedd lt:uf urca FungJc¡dc appll­callon mcrcascd seed > ¡eld tSY) h) mcrcascd nUmnCf\ ,)f pod~ per plan: (pp¡, RUSl severity \\'-1S S{fong!) correkH<!d wlth puslulc de!Jsl!) hu! :hé o\'eral! relat!l:lfi"híp~ ¡¡mong ruS! assessment paraméters dépendcd (in cullrvar aOl.l !<x:al!on Secd y¡eld and pods per plan: were hlJ:!:bj~ cor­related \\ith tAL The TclatlOl1shljh helwccl1 LAI and ,eeds p<r poli (1r

seed weight depended 011 cultl\'(\r llnd 10<:il1l011. 0\'1:'1'<.111 rus! .l"M"~,n'.e!":~ p",rameler~ (ru<;! se\enty aud pWHule den>ily) sbowcd dos.;, ncqall\c reJationshlp:, with seeo yielJ. s.et:'d welght and pnd:s per plan! hUl n(,( wllh secd" per pod, TOe relallO:lship¡, ohtamed 111 ¡he panb¡¡~ n:~hW1H hne 6~R-:W5 wcre les~ dellmtc {han ¡hose In the su~ceptible hné \k\l<.:an 142 The ~lc!d pararr:eICr5. secd yleld and pods pcr plam: ,h{)\\cd <;lrong positive rel¡lt¡onshlp~

Zusammenfassung

Wachstum. Krankhehen und Ertragskomponenten rostbéf;¡¡llener Pllase~ oIus~Bohnen in Atbiopien

!r. behandclten und unbehandelten Bohnenparzelkn. dle ¿ \\oehen nach dem Aufiaufen mil dem Rostpilz ll'(JII1Yc('; (Ipp¡,mf¡wimu' 111-

okuliert worden ",aren. wurden Pfianzenwacnstum une K;'unk­hcitseplde-mien in 2 \'egetationspcnoden be1 :: Sorten all .:2 S[and(lf~en

emmal \~óchenthch bomtiert. Die Kr;mkheltsstarke wurde cm F ¡;ng!Zlu regaherL das 111 fUllf verschledencn Haufig:kcitsstufen ange\\Cndel wurde DIe Fungizjdbehandh.mg heéinfluBtc den Blauflachemnde:\ {LA)) und reduzierte den Rostbefatl Das FungJZld zelg'le keme Slg­

nifikante Wirkung auí andere Krankheüen und die Gróue der abge· s.torbenen Blaufttiche Es erh6h\e den Samenerlrag ($Yl durch eine Stelgerung der Anzahl Htilsen Ptlanze (PF)" Ole Roslstar1;C 1.\J.f lmt der Pusteld¡chte eng korreliert, doch dn: Beziehungcn zvdschen den bel del' Rostbomtur berücksicht¡gten Pammelern hingcn von $orlc und Standon ah. S,tmenenrag uno Anzahl HübeniPfiunle kürrdlerten ellE mil dem Blattflachemndex, Auch dJe Beziehungen zWlschen LAI und Anz<lhl SumenJHülse oder Samengewichl waren 'ion 50rte und Sttind­ort abhiínglg. Die he! der Rostbonitur berücksichtigten Pammeter Krankneitsstiírke ulld Pusteldich¡e zeig:ten enge, negalive Belléhungen .lU Samenertrag, Samengew¡cht und Annl.hl Hmsen!Pftanze" aber nichl zur Anzah! Samen:Hülse. Bel der teilresistentcn Link 6-R~395 waren

JIC KorrclatlO!lCn \\ClEg.er deutllch ah he! der anf:¡:ltg:t;"!1 Lmle MC'üc4n 1-+; DI!? Erlrag"pm.lmeter Stinh"nertr:tg amI An/klhl Hulsen Ptlmlze 7:1F!~n ;.l<lrl-:;: posltI\e Korrdalwnen.

I ntroduction

Rust cau~ed hy Cmmyel',\ appendicululil-l Pers, (Cnger) IS a \\lde~sp;ead and important disease ofbt:ans (P/wwolu.\ ru{g,ffrJ';

L 1 in eaSiern and 50uthern Afnca. In Etbiopla. severe OUl­breah o:' hean rUSl \vere reported from the south and south~ \\e<;tern p¡jn~ (lAR. 1974}. Asevere outbreak of bean rust re5ulled in nearl~ IDO~~) Yleld !oss in the popular and wide]}' growo, but -susceptihle cultí\'ar. Mexic:m 142. Hovvland and \lcCartne:, (19661 and Singh and Mns¡yirni (1981) suggesteJ that a Se\efe infect!oJ1 of rus! !na)' CHuse <i I O_··37~.'¡, yield JO.5:\ in Ea~t Afríc¡¡.

Tl:esc nndll1gs \\ere mosll~ ha~ed on visual obseryation. Few q:Janlllatl\ e dala e\.lst that sho\\: the impaC! 01" rust 011 erop g! 0\\ th. Yleld ~md ~ lcld components. Analysis of crop growth and yieid components affected by rust should help ro under~ sHlnd lhe relatior.shlp belween the production situaLÍon (De \\. il. ! 982 L disease and yleld (S¡:lVar~ Hlld ZaJoks, 1992¡¡,b). The tolerance of a crop to injury varíes duríng the growing season iZadoks. 1985), ane so anaJysis of crop growth. disease de\elopme:1L yield ..:omponems and their interrelatiol1ships at \<uio'Js constramt ievels \Vil! help 10 undérstand the pro·

¿uctJvJty of beao crops i11 Ethiopia. Management uf crop loss (Zadoks. and Scheín. 1979: Mack­

cnzie. 19831 reqUlres a good understanding 01' rhe re!atlOoship between crop g:rO\\ th and disease development Savary and Zadoks. (191i2a.bj established relalionships between prOdUC\lOn situatiom. injury and damage in a groundnut multiple patho­~~ \1em. In beans. no such relationships were s1Udied, Exper­¡mental mampu!alwn of epídemtcs is one way lO jnfluence crop grmvth. dlsease development and yíeld_ This study repons on SUÓl expenmen!s. addressing 1) Ihe ,¡;-ffect of different epidemics on leaf area inde\ and yield components: 2) relationship between diftCren~ paramelers for rus.t asse<;:sment 3j relatíon~ ship between yle1d components; 4) relationship between leaf area indexo rust de\elopment and yield components.

u S ((lP:;fjyhlC!wll(l~eCcnler((;,j~SlatcmC»1 0931-1785;95/4307-0391 S 11.00/0

TJble ¡ DeSCnp¡lOtlS of bean 1!rowlh stagt'~ as llscd in this study. :lrter Fcr~ ;:andez ~{:ti 1 19X6). \\ll11 ;>hgh¡ modific<.:tlons

\'4 = Thml tnfo!tolatc !e:.tf R5 = Pre·l1o\\,'cnng. ::;st floral hud R6 FrO\,t:~mg

R'" .'.". Pod rormallU~ R7,\ ·-Ist week üfpod formatlUl1 R7B~::;ml \\,ce)( or poJ formaHOn

RS Pl)d tilhng R8 I ht week of pod 511rm! R8::~··':tld weeÍ\ or poa fill¡~g R8:,-- ;'Hi week ,)f pod nllmg

RY= Matunt: (discolorauon anJ drymg of podsl

. \'1 atertáls and methods

Experimental design

Fldd ::xpcnm~n:s were performcJ In !99u :md 199J, 10 cxpcrlll1emal fields nI' l:hc InstJtute o( Agrlcultural Rescareh at Dehre ZeÍ! (¡ lS50 musl and ":,:. 900 mm annuai r~:¡jn:aJl) and the P~ant Pro(ectloíJ Re.;iearch Centre al An:b(l ,2l50 musí anu ca. 960 mm annual !'a!nr,dIL

Thc expenmenls v.ere condw:wd ,I~ randomlL\~d L·o:np!elt.': b;ock tló!gns wlth ~¡\. repIKal\0n~" in d '>pln pio: arrangemcn! Two clI!Hvars.

:vIe"iL·a;, 142. \ust~epi!bh: (ses). ,lnl: 6-Rw}95. p.¡rtlaily re~¡Slanll RES). formcd ¡hl;! r;1am rlOb <!!',¿ Ihe ~rra~ ~rc;¡!menh :h-.: \uh·pll}¡,,, Se\!ds \\ere M1'A!l 1:1 lllHi-Juw;: ,lt An:Or' -tr,J I.:url: Jul;; at Deorl.: Z":1t. The I.:xpcnmcnldl JatJ al Deb~c Lt'H In l '191 :'or RES were é\dud::d I roll1 the analysis dae 10 g ~e-\ere íni',:..:tLm o: Sean Common ;\1o~wc VIHI:> IBC~IVl.

Standard .lgronoillll.: ~ractice~ \\cr~' iollawed .md no fcrtdizcrs were applicd, Tite t'::.:pernlH:n¡<J.¡ ~Llb-pk;ts mca~ured '+"'4 m'. Ooe secd rer ho!e \\al;> \<)\\n ,lt.fl) (m tlistance b::t\'el.:l1 Ihe rov.s ano 10 cm di"lul1!:e

\'<ltbm e: rU\\ Llc:: plot \\u~ "l.Irfollmled by 3.2. m gUilrd rows of \\ he.lt lO reduce m[erplo¡ mterft.':rellL'é.

InoculadoR

Threé ~~eeb ¡¡fkr ",mertlcnce, each 01' Ihe expenrnental plOl\ wa~ IOÚ"':U­b[~d by spra: IIlg .\ uredllllü __ püre '-,uspenslt.\¡) I aoom :: g uredm¡q,porc pcr 20 ¡ o( H~Ol contJlOlI1g J ml'cure or !1k~:d IsoLHí!S oí' ryean ni;,!

(o,;e..:ted from lhe re~pe(ll\e !ot:ólllqm.

Spray trelltme-nts

Fuog!Clde "ipr J) ¡ng heg,m 1-\\eeK <Iflel' mOC.lJ¡ltKll1 T (1 produce ept~ demlCs úf \ary¡;:g mtens¡IY 1Il ':<len ..:,;;m;Jr. pmot,u\. ~{)"/" {oxJ~

\-"arÍ'oxln. a ):,tcmlC ,·uoglC:dt' ,tI rhe rate ,)( 0,[%) \\;.1 .. "pplicu ¡jI mterv:ds ,,1' 5 Hre:Hrr.cnt '+).10 Hreutmenl 31. 15 (treatment 2¡ J.od ~O dll;' s ¡Ireatmo:nt ¡), A che:.:k {tH.'.ltment O) \\;¡} lef: u!1spru) ed Lo allo\\

maximull1 Jo:\ dop1ne::! <>( bea:: -u»1.

Crop a~-<;t'.ssmt'nt

Growth ~t.IEC\ \Vere det,,;rm:!~cd ~U ~h<é' J.tt6 ;.'1 Jbea~.;;: .l,,~::~smení

{ollo\\u:g F"rnandcz .él ,;l. \ t9S61 \\ ith ~hght modílicatWl'h (Tabh.' 1). A~ the lir'l; ,mo:! la~t dl~<:,\~e ,Iw:~~meot .. 1.:W:'. lh\:! l1umber 01' pl,uns In ¡he mlodl" fOllr ro\'",> nI' ~ad¡ p!O\ \~ ¡t:. coúlHcd. C\1llnb were cúnvcfll'd to p!anr dcm.n: {th\!OreHc~ll!y 25 r!atns In :j, The leal' ,m:a al' cUi..'h pL.;n\ .,dected t'nr J¡se:l>.e :bscssmC'1H WdS ..:akula\ed: u~mg :1 pil.:tonal ke:. The te,l! _\re"l índcx i LAI) '.us Jete;m:neu ~lt wceld~ murv¡!ls.

DisellM' ll .. .,cso.¡ment

Frnm dbou; I(! Jay\ aft~'r ;n\)<.:ub\lOl1. a~.,c~¡;mCl1¡ ,_1f ;l1c¡dcm:c (;)umb,~r

úf Inf..::l'tcd leaYc\ per pldlH), .\c\.:nl) lpefcen! ¡"al' drea Inré':kdL ptl\luk' d..::n~¡¡~ (Ilum~e:" ni pu~ade~ per kan. :mJ pu.,wlc ,1/":: (¡ = IlU \i~¡bl..::

... ~mrtotll;,: ~ = nt:\.:rr'uc "rOl\ \\llhoul ~pnru;¡¡lJún: :; = JI:ulletcr ,11

... -¡;orul.1tmg pumdc: < 300 pm. 4 300~500 ¡1m; :' = 5(l(H~OO ,!1m: (1 o,,: > SOO ;1111) \\¿r;::es(Jmalcd iSt,!\cly ¿t aL !9XJI ut weckh IIlterv.!:~" Oh~o:nd[I{)m \\cre mad..: ,-)11 ::: randnmly ~t:k-l'wd 'IDO niark¡;-d planh

HARTe and ZADOKS

¡x-r plot. \.1.vO!ding plot borccrs. We!l-¿c\i;;loped greco kaves rat:domlv ,;e!et:ted ano repre$en~mg tht uppe. mldd!e CI!)d !Ower c;:núpy la~er's \\ere used for Jisease a~~eSSme:1L Tltese taggcd plants j noo~Je.\trut::¡vt! ~ampl¡og) 'Acre used on each oh';'CT\ a\lOO da::

O!hcr discases sl.lch .1:> cornmon bucter:al bhglu f X<lnfh,!ll!Ollü," {UIIi­

J!C'f1ri, pl/. phascoif (Er\\, Smlth, D(l\\~on) ~t Deb:c ZCH 40d all[hnu.:.

IlO"t' ¡Cu!!e¡utru!mm lindc/1/lIlhWllum ¡Sa;;:c JnJ \tagn,!j BrÍ. ¡.md CJ\-.

al Ambo. yello\\'mg ¡¡no dcad l!~~Le Irn;l1nh ~n~e..:t 0c\maue ¡-¡nd 'ilígh! nec-ro~IS} ",,",ere ússes:.:cd ,>cparatel). ,\¡ Ambo. ,Ct'Ú" \\e,e -trcatcd \\i!h

bcnomyt {Habtu ami .,.-\.-wgeche\\. t 98-+: pON io r!a::tmg becau~e 01' lhe higb mCldence oí unthracnose.

Víeld assessment

/-\t the enU of {he gro\\ In); seasoo. "e~d \ leid ¡ ~ '1 I 111 :r m :. seed wetght l$W) in mg secd '" number ¡)f pod" pLun I PP:. ,lod number of ;;ceds püJ -' (sr) of the four cen:rlll rO\\ ~ \\er:: .J)~ó:>ed, SY J.nd SW \\'erc determmcd at ! 2'% m~;¡5(ure .. fter <;un-Jr~ ing lhr6;wd seed:-\ for 5 da\-~ . PP ltlld SP wen:- counted dl ¡lar"e:.!.

Computation

Cru"s-.¡ecl¡únal aOJJy)c,> iZudnks. 19:8; "e:e ..:onducted ro check ¡he ctfects of :reatments o:, LAI. dl'>ease llHeO\lt:- lrus: mCldcoce (lN l, rust »C\cfH) ¡RS). pu:.tuk dens:;: [PO). plbW:t: .,:zc ¡PSi. )e\erJtv or'o¡her dú,'.;a,cs ¡OD) .tnd de;:.J tN¡¡C íDT.I) :;er (dn0r~ LI;.cr :md ~r growth ~l.¡ge. Tht! anJlyse" ¡~)led 1'0:- che ell'ects 01' ..:ult!\',¡r. treJtmCn( am! ll1tcrao.:tlOm 01' cUh¡\',lrs b\ trcu!ment~ ¡e"Ti. e c~rr,Clen(~ 01' ,,'o~relatlUn

of rliS: Jl1telblt:, ~aran;ete¡s Il~. RS. PD . .1:,:13 PSI \\ere caJculated ;0 delermine mutual i'~L.itI"mshlp'" St¡w~tlcal ,lnu!:ses were performed u$ing :víSTAT (Freed e[ al., !I)%). ,-\E rC,b ror ~LgmfkHnce were pcf­

formcd at P ~ 03J5"

Results

Production situatiou

The product!on S1tU;1ÜOll is ..:har,!CEerbo( ¡)f lO\\ :nput agn­I.'ulture. witho-ut N. P t)f water Jdd~d (Oc W¡L 19R2J. Ambo h.a~ more r:'¡!:lY da) s, more c10ud CO',~L lc\s radlatlOl1. cooler nights :.md higher rust pressure rhan Dcbre ZeiL Yídd c¡¡p¡wity h

:-efleci.::d by lhe average maximu:1l y¡dJ í:.leld lit' the rust free plotJ of 1860 kg ha -1 rOl' SLS .tt Denrc leit dud hy lhe maximul11 y[eld 01' 2¡;.:0 kg ha -1 101' RES:t1 ·\mbo.

Effects üf spray trcatments

L"af arel! intltx

Differences in LA! between '>pra:- trC~tlm.::n¡s \Vere significant fmm f}O\vering (R6, onward:, lTable 21. III 1990" :lnd al a!l gro\\th ~tage5 In 199~ (Tab~e ~l. lr: ses. LAr rC<lchetl a maxirnum of~.25 al "rnbo iY90, ~1J~d :,::1 ,lt Dcnre Ze:t !9(}L bOlh in treatment 4, For treatrnen: -+ L \1 rc~;...:hc;j it) maximum

.lt R 7A. al R(} ror the otile: trc.HI11l':lh. t!len d>t:chned. file decline \\<1:-' most prominéllL (01' t;-c~\tmc'l1l O RES abo :-.hO\\t'd slgnlficant dltfen:nc0~ bet\\Cee ::,pra~ lr-ca::11-:nh, btJt [he ditfer­el1ces \vC're not large. Diflclcnccs net\~een (~tit¡var:-. were ~ig­l1¡tkant (lt V4 and '-it :;?:RiR Ar 1\\0 grO\\th ~tages tRi) and R'» lhe intcracrion net\\een culll\'ar and tre;H!r.:erH iC*T) \Vas

~lgnificant. In Debrc Zeit 1991 the block crfec~. sigmfh:ant ar all gr0wth ~tages. re!leckd the w¡Herlogging kommon al Dcbre ZelO th¡tt ~t!rected ;;ome tre¡lttnenh

IIIl.'idt>ncc

In SL:S at .4.mbo 19í.Jü. ru~t lilcdence rcacbt:d lIs highe~t len;-! {Soo~;d in trcatment ít Ddferences be!\\cen ireatlh;:nts were slg­mocan! al al! stages Jf crop dl;!'\t'lopmcm íTable 2}. In RES rust inddence never c:\ceedcJ 25" 'L The tremi in RES \\as simildr to tha! in SL:. <:\cept ror the n:;.¡g:nHud¿> ;)f the- difft'renl.:<;:\

Rusted Plw.\('(JJ¡/1 1:3<:.111' 111 Elhll'rW :193

Tabk ~ Cros~~~eCll(ma! :111.11: '1' (Ir efteCl:- of treatme11ts on LA.!. inCldencl;:'. se\'enl~ . dcnsil;'. and PUqu!e ~IZC. Ambo. 199(1

-.~-_._------ - . --------- ----------

V,mante ratln \aJue~ al GS= ---_.- _._----~\)llrte 01 ---_. __ .-

\"c\rlahle~ \.:rution V~ R' R6 R7A R7B RXI RX2 R~3 R9 -------- .. _. --- ._-- . --_. _. __ .. _---

LAI Cultivar--, 14.0 n' '" n' 6.4 N.I IY.4 94 2:'i.Y Tr(',llme1l1, ~J) n' 5.0 Il} 4 160 1'10 21.¡'; 23.3 19.7

C'T 4.1 n, ns '" '" 3.4 40 4.7 2.7

IncIdente e Ultl\,H~ 23 - 3:' .; 156.7 67.1 8:2.7 n.7 In.o 6X 4 10.1

Tre.lllnel11~ 3S.4 31.2 n7.1 74.3 77.5 10H 60 20.3 6.6

C"T ]3') 9.' 62.2 :lb.O 44.2 4:1.5 lX.3 S.N 3.1

Sevenl)-UCP Cultivar, n' ~ (1 117.3 15. 7 1'1. 7 20.0 13.9

TII;:',ltmenh '" :' ;-.: 65 1 57.2 ,1 , 16.6 12.7 C'T n, n, 16., 14.1 66 7.9 6.7

-Me CUllIV¡H ... n~ , ' ns 19.5 106 Trealmenh 1"74 16 o 11.6 16.5 7.4 C'T n, n' n, .,.9 lb

-LC Cllltl\ar~ ns ns ns Trl;:'Jtment, 6.0 4.0 4.9

C'T n~ n, 5.3

Denslt;.-UC Clll1l\'ar~ n, n~ I ¡..;. '7 2l'1.1 21 (J 10.0 ns Tr<.":\tmenb lb 6.0 :16.6 36.1 29.:' 1 S.ti 16.11

C"T lb lb 9..1 n 10.1 6.0 5.0

-MC Cultl\ar~ n, n, 10.:1 lJ.2 9.6

Trl;:',ilmenb lO.:' P.2 16.0 10.7 7.1 C"T n' n, J.7 :U 4.5

-LC Culti\ars '" n~ m Treatme111s 131- 5.7 C'T n, 115 3.1

Slze-UC Cultl\'ar~ ns n, ns Il~ lb n, '" Treatmenb n, lb 14.2 3lJ.¡'; 17.J 13.9 13.8 16.4 C'T n, ,~ 4.4 '" ns ns 5.:'

-MC Cul!i\ar~ lb n, "' ns '" Trl;:',l1mellh 20.() J~. 1 :19 .., 13.0 ~.2

C'T n, lb 3 5 ns n~

-LC e ull1\ ar\ n~ n~ ns Trea\lnent~ n, ' o 11.4 CT 3.2 n, 2.7

~ns = no! sIgnifican!. - = not deterrnmed. al! othen. ~lgnilicant Jt P ~ 0.05 ~UC = lipper canop~ l.\;.er: MC = rnlddle callar: layer: LC = lower callop) layer.

between treatments. In Debre Zeit 1991. differences between treatments of SUS \\ere not quite a~ large as in Ambo 1990. Significant ditferel1ces were obtained belween R5 and R 7 A (Table 31.

At Ambo 1990. inreraction effects between cultivar al1d treat­ment (C*T) were large and consistent. Al Debre Zeil 1991 the block effect. significan! in 4 out of 8 cases. \Vas largest al the earlier growth stage~.

Rust se\ferity

bpper canop~ layer

For SUS. rust sevenly reached a maximum of 55% al Ambo 1990. and of 15 al Debre Zeit 1991, at R7B in treatment O. In Ambo. differences between treatments. significan! from R5 onwards. were highest at R6 (Table 2). For RES. rUSl devel­opment reached a maximum of 15 in trealment O al Ambo.

and significant differences between the control and sprayed treatments were obtained al R7 and R8. At Ambo ¡here was no block etfect but a significant C*T interactlOn was found from R6 onwards. Al Debre Zeil (SUS), differences between treatments were significant al R7B and R81 (Table 3). Block effects were consistently significant.

.\Iiddle canopy la~'er

In SUS. rust severity reached a maximum of 50 at R7 for treatmenl O. In RES the hlghest rust level (18) was found at R6. Differences between treatments in RES were significant from V 4 10 R 7B. Significant differences between cuhivars were observed al R5. R 7A and R 7B al Ambo. The only C*T inter­action effecL observed al R 7 A. was hlghly significan!. At Debre Zeit. treatment differences were significant at R6. R 7B and R81. Block effects were more common in Debre Zeit than in Ambo.

_,_9_4 ___________________________________________ .....:'HAlHe ",nd Z,\DOKS

Tuble 3 Cro,-s.-~ect:ona¡ ;.mulyslS of ctfects 01 trcútments on leal' area index. inclde!'.ce. $evcr,t)'. density. uno pustui~ SI/C, Dehre Zdt, I~N!

V<lfwhk'j Vanunce rallO \ aiues ..ll GS ::'

V4 R5 R6 R7A R7B R'l Rt\2 RS3 R9 ._ ... --~~~---- ~ . . ---_ .. - _ .. __ . __ .-

._--~---

LA1 3Y 5.7 JI.! 16.0 2íUl 15.0 !0,6 ¡ l.~ 3.4

[o<.:ldence n> 9.~ 11.0 7 ' ns n,

Sevent;rCC ns ns 7.6 6.5 -Me ns 5.9 ns ; 7.:1 .::!7 o -Le 40 8 :2 ns n50

Dem.lty-CC ns '.0 20,9 164 -Me ns :-:.1 '.3 11.6 ¡s.g -Le '" 6.: 11.'1 ns

S¡¿e-LT Ih '1.9 :':,9 -MC ns 16,7 1 I 3 1;.'1 -+.8 -LC ns 6.4 s. ¡ Ih

--- ... _,,---- .-,,-~-- .---~--- .. _--':1~ =.', not sigmficant: - = n(ll d~termmed: dU ülher .. ~\!Illricant.l( p::;; {) o:" 'ce"", Upper CU(l0P:; ;,l!er; Me = mlddle c.t:1Upy l,t}~f' Le !o\~ef :.'<.inop: Ll:;C;,

l.l).wt iallfljl; lal ~r

Ru:'\t :.évcnt;. .j::dmeu a:. the se'iI$on progrtssed. Fnr tlle control plOlS oi' ses. alst :-.eHnly decrea~~d fmm :0 tú 5. In Ambo. (loi: three ,l'),c~)menb \\Cfe done on ¡he lmver ,;anopy layer el:.­

ka\cs heg:~!l1 (,1 dro!' al R7A. Trenus in SUS :mJ RES were Sl!mL1L Dc~p,t,; ~ow disease '.\tiue::.. differcnces oet\\een tre~n· Glents remmnd sigmlic:.mt. At R6 C''T inreraction \.\'u~ slg­mfi":á:H tTubk:l. In Debre Zell ~ign:f.cant diffcté.'llt.:t':S bemeen treatm<:nts \\~rt obtain"d at RS and R6 ¡T<¡bl.: 3),

Pustule densit]

t PJkf l':m(¡p~ I:HU

0l ulilbers of pu~tU!eS reacheJ a maXllnum nI' 230 pustulcs rer leal' for trea:mo::lt 0, fn Ambo, dlffercnces betwcen t:'¿almertr:. \\crc ):gninC~!I~t ':rom R5 í(l R7. Thc trcnd remml1cd the ~<Ime for lymh cultJ\ d;'), but In SLS Jcn:-.Lty \vas bighcsl alld qtríatJ(}n bet\\tel1 treatJ~;,;:ít5 \\~b grciH6L In SUS <H Dcb!'e Zeit. despllt: 'ilfn1l1cant d:tr,,:~~nces I R '"7, R8¡ bct\\et.:n treaunents, dén"ilY \VjS

rather ¡Ü\\. l1L), :'\céc,hng 60 pustu!es per leaL

\liddlf' caf1Op~ b:u

In ses at Am0\). :he pu,tllk densa)' dld not t:xt,;ccd 150 in ll:iddlc C¿IlOP) "I\"er. .\t VJ., pu~tuk dcn~lt~ w~¡s ,llreaJ:y JO pcr lcaf f0~ trcutmc:1t O. la RES pll~IUk de¡:s,l~ \\.a~ klW lhrüughour lile ";C,lson Jr:J ;J¡nl.:-:·C'fi(eS al1l0ng treatments \\ere :->1U<.11l but ,lgn¡fi,:ant. begl:~nlllg ,H V4. A ,igmncaJl1 C*T int¡,;ractlol1 wa, tound.H R6 ,lr;J R 7, In Debre Zcll, treatmCl11 etfcCls. rem,¡ined ~ign¡rictnt aú¿:' R6 '.'.¡lh highc)( diffl!Tel1':CS al R7B anJ R81

tu"'''' Gmop~ laH'r

Ru~; \\;b 111~: .. .,b..,e:-vcd hl th.:: lov • .;r ":~IIH.lpy layer. :\s the crop de\·t'll1ped, le" \ 0:' wJth íH,s.tules \\crc r..:mo\'cu frn111 lhe ¡nfedion proc;;:" b~ 1l0r"1;¡¡ !cal' drop and ;-m:,~n puslUle tÍ\!l1\ity \"',.!S

rcdu..:cU. Fl..ll" SL S ami RES in Ambo. diftclenCé"'> net\\ce:l trcat~ !neub \\~n~ "I::p~ltJcan! \\](11 ~lgmficant C"'T intcr:lctlOn al Ro lJ: O<:Or:: ZeH. (be resulb \vere similar ano Jilferences bClWé"en ¡re.1 ::neJ"!b \\ efe ,¡gnificant

6.00 ,

iJJ .) '2 (f)

".j (J)

:J ~

2 .. U) J") :J ~

1.00 '--__ -I.:t:l_ , • Spray freauenc¡es

• sus ORES Fig. I E¡rL'¡;f¡,lf ,pr.;y tn:.lUnenh ,m ptb¡ul-t <;jL~, Ambo. ! <)'10, JI R - \, Data \ alues dI;;' mean of :..;.ppet. Il1lddle dUO hOllc'm (",jlJUr: 1.I:e, B!"d, ¡;OIUrtl~h. ses. \\ hile w!umnii. RES, E...¡¡:1l ;,:oIUI1111 h lhe mean t~f )\:\ r("p¡¡c,H:on~

Pustule size

L' ílpt'1" I.':mup~ Ja~ t'r

In 1990 al Ambo d¡tf~rcn{.·es in "lze úf pu>¡uk~ J:nong rhc lreatmcnb began ¡o ,ho\\ at R5. Dítfere1H;\!s ,lmunf! trcat1i:ents were $trol~g ~lt R(J w RS, Th\! trend \Vas similar f",r hoth cu!ti· v;.lrs. Differe~lCC$ bet'0.ten tn:alHiel1b were laq!er ll1 SL:S [11.ln Jl) RES (Fig 1). For SC,:S In Dehre ZClt, \.lLtfen:Ecc~ bct\\een

lreatment5 \\...:re ::.ignttJc:mt aftl.'r R 7

\liddl .. \."¡)JlU¡): la~cr

Whclí bean erop:; were not sprayed wlth :'Ut1giddes. [!Usad;;: ,,:i.,:e .:ontinucJ ro ¡naej~e" Dilfercl1cei bel\\een tre~11111e!ltS werc :-igmlkant :¡t':er V·,t in Ambo_ 1990. ell1d aftcr Rú in Debn: Zelt. 199 l. In Ambo. ~I s,lgnitl.:ant C*T mtcra.:tlO!1 \\ el" :'ound .H R6.

L .. wcr (";lIWp~ la~~r

lE !Í11)'>,l t;:bt). lh\! dau \\tre cOlketeJ onl) (bree 1¡n1.:;,. due to fa"t ddóliallol1, All :,pra~ treatmenls resu!tcd In a reJut:eu ru;.~ tule ~i.'.e. As rhe crop dc\CdopeJ. reducríon 01' ru~tllle "ILe \Veh

~üntmuollS for .tll :-.pra;. lreat:l1ents, Trearmem O fo::-.ulted ¡n <1

Rusted Phaseolus Beans~in::..:E::th>c,ú~p::.:ia=---_________________________ _ 395

(jl

T rt

e '00

>­UJ

,. ,L -'r-~~------------------~

, • •

Spray rrequenc¡es _ sus C::J F'l?:S

, •• r-~~-------------_,

ID o.

~ " ,

.. , • ,'r---------------------,

~

e ro "

o

jI]

I

• Spray frequenCles

_ sus CJ FES

Flg, 1 Effecf of spray treatmen!s on )'Icld pararneters, Ambo. ! 990. (Al" seed yíeld (SY) in g pe: ID -:; (BJ. seed welghl (SWj ín mg: seed- 1: (C),

number of seeds pod-' (SPI: (Di. number of púds plant-) (PP). Black columos, SUS: whue columns. RES: bars indlt:-alt SD. Each eúlumn is the mean of si>: replications

large pustule size. especially in SUS. In RES, differences be[ween treatments were significant al R6.

Otber diseases

Severity of other diseases. mainiy cornmon baClerial bl1ght. anthracnose and ascochyta blight did nol exceed 11 % in any ueatment. Differences between treatmenls were non-significant except at R6 and R7 in the upper canopy layer. The trends were símilar for the two culü\'ars. Disease intensity increased from upper to iower canapy layers.

Dead 1íssue

In aimost aU cases (except the middle canopy layer at R5 in Ambo and the uppercanopy }ayer at R8 and the middle canopy layer at R7B tn Debre Zeit) differences belween treatments were non-significant (P ,; O~05), In the upper canopy layer dead tissue did not exceed 10% whHe in the middle canopy layer it ranged between 10 anó 15 ror SUS and 12 to 24 for RES~ In tne lower canopy layer aead tissue values were up to 30.

'\~teld and yield compooents

Seed yield

In Ambo (Fíg. lAl; seed yield varíe<! from 24 g m -, to 156 g m-'ín SUS and from 153 gm-'t0218gm-'in RES. In Debre Zeit in SUS (Fig. 3A), values ranged from 106 g m-' 10 186 g m -'], The range between the highest and lowest yield value was 132 g m- 2 for SUS and 65 g m-~ for RES. suggesting an interaction effect of spray treatments and cultivars. Close exam~ ination of the graphs (Figs 2A, 3A) -shows that the interactíon effect is largely due to treatment O where no spray resulted In a significantly lower yield for sus. When the disease pressure was low, as in Debre ZeÍt. the range ín SUS was only 80 g m~:. Differences between cultivars and treatments were significan1. In Ambo, a significant C*T interaction was found (data not shown).

SwI ",eight

Spray treatments increased seed weight ln both cultivars, but the effects were slight Differences between treatments were significant Seed weight ranged from l25 mg for treatment O tú

150 mg for lreatment 4 in SUS and from 130 mg to 147 mg in RES (Fíg. 2B). The range of variatíon for SUS (25 rng) was larger lhan for RES 07 mg), In Debre Zeit. seed welghl ofSUS ranged between 124 mg and 136 mg (Fig. 3B).

Seeds per pod

Seeds per pod ranged berween 3.3 for 4,0 for SUS and 4,1 to 4,7 for RES in Ambo. and 3,5 to 4.1 for ses in Debre Zeit. In Ambo, there were significant differences between cuhívars (Figs 2C, 3C). Differences among treatments in both Ambo and Debre Zeit were small except for the dift'etences between sprayed and non-sprayed.

Pods~ plltro

In SUS. pods per plant ranged from 2,5 to I I ~8 ín Ambo and 11.8 to 20,0 in Debre Zeit (Fig, 2D), In RES. at Ambo, the range was between 10.9 and 15.9 (Fig. 3D). Dífferences between cultivaís and lreatments were large in Ambo. Significant C"'T interactions were found, located mainly in the contro.st between sprayed and unsprayed plels ofS1,;8,

Córretations between parameters for rUS! assessment

Table 4 provides eorretation coefficients (r) for the reJationships between the vanous beao tust parameters. For SUS in Ambo, the r vaiues increased as the crop deveioped, being iow at V4 and R5 aud hígh at R7 and R8~ Híghest correlations ()oQ,85) were found between rust severity and pustule densiry at R7A~ R8L For RES the relationshjps were relatively low and unre­latOO to plant development. The r values were highest at R5 for pustule density and incidence or rust sevcrity.

396 HABíU and ZAOOI(S

.. , 1) n,

A ID B

'oo 3\ , .. 1 ID T ~

ID Q .. , Q

Ol

~ 80~,

e 100',

··1 ~ ':l <;; (1)

S Ul .'

, "

'Q e ~ D o • e el. ro

Q ~ • QJ ~

el QJ el

¡j) ,

u (J)

ID 1) (j)

1', O

0~ CL

, , • , • • • ,

Sera}' '¡;"-equencles Spray frequenCles

Fig. 3- Effect of spray treatments on :I':!;] ;¡arame:ers, Debrc Zea, 1991. (A) seed yield tSY) in g per m - '; (B) $ccd we¡ght {SW) in mg se-ed -1;

(O number of sceds pod-¡ {SPl: (Di number of pods p¡ant- I {PP). Black columns. SUS; RES failed be>;ause of Vlrus :wack; bars indlCate SD. Each eúlurnn 15 thc mean of SiX fephLalh)f\)

rabie 4 Lmear cúrrelatlon coefficíems ¡' between rust parameters'

"'-._--" .. _--_ .. - .. ... ----- ._-_ . Growth Stage Locat¡ón Y::::H ((,¡L IN·RS' IN·PD IN·PS RS·PD

.. _---_. __ . ---" '-'--' --_ .. .. _----_ .. V4 Ambo 19'ü SUS ns' 0.47 0.64 036 R5 ns 039 0,70 0.69 R6 0.63 0.65 0.76 0. 7 7 R7A 0.12 0.83 085 0.89 R7B 0.79 0.84 0.79 0,93 R81 0.76 0.82 0.76 0.88

V4 RES m 0.77 0.73 ns R5 0.73 0.87 0.79 0.86 R6 ns 0.55 076 ns R7A 0.56 0.4.2 0.68 ns R7B 0.63 0.36 0.61 0.6ü R81 n50 0.38 0.53 os

R5 DZ 1991 SUS 042 ns OA5 0.63 R6 0.44 0.53 ns 1).59 RíA 0.49 053 os fHl R7B ns ns 0.39 {) 82 RSI ns os ns 0.63

M~ •• __ •• __ ~. __ • .. _--- ._ .... _-~ ... --_ .. _-_ .. .lnumber 01' plots lo test correbtlOn 3015 treutments by 6 replíc¿¡tíons), ~1r-; """ fUS( mcidence; RS tUS! severity: PD pustule dens¡ty: PS = pustule size: LOé .... lo.;;atlon; Cul = cultivar 'nll = not :ilgnrt1cant: r values'?: O 36 sigmñcant al P ~ O_OS

--_ ... _-----

RS·PS PD·PS

n, 0.51 0.47 0.59 0.74 0.&8 0.79 U.84 eSI 0.71 0.&2 0.75

0.46 0.&3 0.59 O.Ú5 0.55 0.63 ns ns

0.53 0.64 ns 0.65

0.56 0.52 0.38 os 037 ns tUl ns ns ns

•• ___ • __ ._M

Rusted P1UlSt'Q!IlS Beans in EthlOPW 397

Tabte5 linear correlatlotl cúeffidents between LAI and pod~ per plant ¡PPt :>eeds per pod (SP). seed welg.ht íSW). and seed yield ¡SY¡

Ambo, 1990 sus

Growth stage pp' SP SW sy pp ... _-_ .. _ .. __ .

~~_ .. _----V4 O 41 h ns os 0.49 041

R5 0.41 ns ns !J :'0 0.:-R6 0.54 ns lb 05ü (J 69 R7A 0.75 os o-e 0_:;' Ü 80 R7B 0,86 os 041 0.82 07& R8-\ 0.86 0.42 ti 50 0.9.' 0.65 R8~2 0.Q1 0.46 0.56 0.93 O gO R8-! 0.86 0.58 {).~4 11,8- U SR R9 0.84 0.54 0.:::5 0,90 ¡j 81 ---... -" ... _---_ ... 4number of plob tú test correlatlon "" 30 I S ¡reatme:1::~ hy 6 repl!catlOnsl bUS MI slgnificilllL r value ~ 0.36 SI¡plll1cant at P ~ 0,05

In Debre Zeit. high r values were obtainec between :-ust severít) and pustule densÍty at R7A-R81. In Debre ZeiL cor­reiations between incjdence and orher parameters were poor compared to Ambo, especially after R 78. This is under~

standable sínce in Debre Zeit differences between treatments were not signíficant after R7B. as appostd 10 Ambo where they remained significant at all growth slages.

CorrelafÍQDS lretween leaf átea inaex 3l'íd romponents of yield

Leaf area index (LAI) and pods j)«' plant

The correlations between LAl and peds per plam were ahvays positive (Tabie 5} ánd attained high leve!;;; hetween R7B and R9. For RES in Ambo and SUS in Debre Zeit. the coefficients were lower than in SUS Ambo. The developmental trend remained the same since high r values \\'ere found after '?;: R 7B. The híghest values were always found at R8. For SUS in Debre Zeit, resuhs were slgnificant from R7A onwards, with hlgh r at the end of RE,

Leaf afea lndex ami rottd ... per pod

The correlations between LA] and seeds per pod were weak, especially between V4 and R7/8 for SUS and lacked a devel~ opmental trend for RES in Ambo. Arter R 7B. especially for SVS in Ambo, rhe relationship became stronger but r dld not excecd 0.58.

Le:af 1IH:a ÍIldex amt sood W1!ight

In SUS in Ambo, {he correlation between LAI and seed weight became stronger as the crop developed with a maximum of r = 0.56 at R8 and R9. The r values were generally lower for RES than for SUS, Overal! the relatlOnship was weak. In SUS m Debre Zeit and RES in Ambo the relationship did not follov.: any pattern of crop developmenL

Lear area ¡ade" and seed yield

The r values were genera)!y high [or the correlation between LAI and seed yieid. increasing with developmental stage. The trend was the same in al! experiments. The highesl r values (;;'0,85) were obtained at R8 for SÜ, and RES In Ambo,

Ctmelati(lns betw{:eU rust and components uf yield Rust inddm«: and yield C"OfOpouents

For an parameters (data not shownj variation among cultivars. locatiolls and growth stages was high. For rust incldence and

Debrc Zen. 1991 RES SU

.... - -- .... _ ... _-sr S\\' SY pp sr sw Sy

.. _---_. 0.41 ns 051 ns '" ns 04\ o, ns 0,83 ns '" ns 0.56

DA? ns 071 os ns os 0.51 m_ Ü 43 0.82 0.55 ns ns 0,70 ns 0,53 0.61 OA5 os m ¡173 m os 0,6l 0.68 11$ 0.36 0.65 Ih :1~ 0.87 O.6i os ns 0.71 ns 0.48 0.85 O.n 051 0,66 0,81

O}ó 0.42 11.69 0,59 OS1 O.sq 0.48

seed yield, r valucs ranged between ~0.38 and -0.71 for SUS in Ambo and Debre Zeit. \Vith RES. the r value was slgnificant (P" 0,05) only al R8L For SUS!' peaked al R7B.

A similar and consistent result was Obtúlned for incidence and seed weight for SUS in Ambo" The rc1ationship was sig­nificant al all growth stages with high r value~ at R8. In SUS m Debre Zeit sigmficance was found onl)' al R7 and early R8" At bOlh locatioos r peaked at R 7 aod R8. For RES re,olt, lacked consistency. though significance was obtained al R5 10 R8. The r vaiues were genera U)' lower for incidence and seeds per pod. ranging belween ~OJ8 .nd -0,65. Far RES in Ambo. r was higher for incidence and seeds per pod than for incidence and seed yield. or incidence and seed welghL and r peaked al Ri-R8.

High r values were obtained for the correiation of incidence and pods per plant ranging between -037 and -0.79. In SUS at Ambo. r was significan! at al! growth stagcs WJth hUle variatl0n. ln Debre Zeít the r values were significam at R5~,R 7. For RES the correlations of incidence with seeds- per pod and pods per plant were better than with seed yield and seed weight. Differences in the relationsh¡p betwcen localion and;or year \Vere cornmOn and variations wcre Jarge for RES in Ambo and SUS in Debre ZeiL

Rust lle\'cnt) aOO yiel4 «(lmponen,s

The correlat1on coeffidems for rust severity and seed yield showed variatíon among cuitivars. growth stages, locations. and canopy iayers (Table 6), For SVS in Ambo. rwas significant at almost al! gfowth slages with peak values at R7, In Debre Zeit. r was significara at R6···R8 for aU three canopy layen;. For RES. the relationship was weaker, with a sIgnIficant !' only in the upper canopy ¡ayer af R8.

The situation was similar for correlation between rust severity and seed weight reiationships. In Debre Zeit. the r vaJues wefe stronger at R7B-R81 in tbe upper canop)' and middle canopy layers. In RES. significant r value.s were oblalOed only in the upper canopy layer al R 7A, rniddie canopy layer at R5 and R6, and lower canopy ¡ayer al R5

As to the correlations of rust severity and seeds per pod r

was rarely significant in SUS in Ambo. In Debre Zeit, r was significant al most growth stag~1i in the upper canopy and middle canopy layers. F or RES. no consistent trend was found but significance was attained occasionaUy.

The correlations: were better for rust severity and pods per

398 HAIlTt: und ZAOOKS

Tabíe 6 Linear correlation coeffkiems'" between ru:st severity ano yield parameters

.~~_ ... ~~~ ... . .. ~-----_ ... ~ .. ..~ ... ----~. --~~ ...

Ambo.l99il Debre ZClt. ¡ 991 SUS RES SUS

.'~-_."-- .. _-_. Leuflayer Growth stage Sy' SW SP pp Sy SW SP pp Sy SW SP pp '~--~~ .. ---_.-'" ._-----_ ... . .. ~--_ .. . .. ----~.~~_ .. ~~

IX' R5 ns' ns ns ns ns ns -0.48 ns R6 -0.54 -0.50 os -0.57 ns ns -0.04 -0.42 os os os os R7A -0.66 -0.64 ns -0.73 -0.41 -0.39 -0.)7 -0.52 ns -0.39 -0.43 ns R7B -0.64 .. 0.64 TlS -0.69 ns ns ns ns -0.39 --o 54 -0.55 -0.55 R81 -0.60 -0.67 ns -0.67 ns ns os os -045 -0.53 -0.46 -0.50 R82 -0.61 -0.64 -0.36 -0.71 -0.41 ns ns .. {).42 R&3 -0.52 -0.6& ns -0.60 -0.41 ns -0.59 -0.45

~C R5 -0.62 -o 53 ns -0.69 os -0.45 ns -0.39 ns ns ns ns R6 ns -0.36 ns -0.38 os -OA-3 ns -0,43 -0.42 os -OAO ns R7A ···0.43 -0.39 ns -0.54 ns ns os -0-37 -OAO ns -0.49 ns R7B ~O.65 -0,65 ns -0.70 ns 05 ns -0.39 -0.75 -0.40 -0.54 -0.52 R81 -0.51 -0.54 ns -0.58 ns os ns ns -0.81 -0.55 -0.63 -0.58

Le R5 -0.5) -0.36 -0.44 -0.49 ns -0.55 ns os ns ns ns os R6 -0.42 ns ns -038 ns ns -0.65 -0.43 -OAO os os os R7A -0.53 -0.43 ns .. 0.62 tlS ns ns ns -0.53 os n, -0.52 R7B -0.45 ns n, -0.48

. ~~_ ... .. ~-~_ ... ~._~-_ .. ..~~~ .. -_ .. ~.~.~~--_ .. '!\.umber of plms to te:;t correlatlon = 30 {5 treatments by 6 replicntions). "ns = Dol slgmficaot: - = nor determinecl: r va[ue ~ 0.36 s!gmficant al P ~ 0.05. Te upper..:anopy layer. Me = middle canopy layer. Le = lower CUfiOpy [ayer.

plane especial1y in SUS in Ambo. l' being significant in most cases, High r values were obtained at R 7 in all (eaí' layers. In Debre Zeit. the rcsult was similar but with fewer cases of slgnificance. For RES. rust severity was significantly correlated wíth pods per plan! ín ¡he míddle canopy layer. In ¡he "pper canopy layer. results indicated lack of consistency w¡th the development of {he erop.

Pustule density, pustule size liAd yicld components

The correlations between pustule density or pustuJe size and ;. !CId components foUowed the general trend of rust severity and yield relationships and thus were nN considered in detaiL

Correhuions 3mong yield rumponents

Significant relationships between the yield components were found (Table 7), excepl for s-eeds per pod and seed weight. r values were consistentl)' h¡gher for pods per plant and s.eed yield relationships. Bean yield is determined by its components,

Sy ~ PP'SP'SW

\\ here SY ~ seed yield, PP ~ pods per plant, SP ~ seeds per pod and SW = seed weight. A simple linear regression of SY with Ihe product of PP, SP aud SW gayo the foUowíng equalíons.

In a muJtiple regression analysis. where SY was regressed ro the mdividual yleld components. with or wHhout two~way and t"nree-way interactions, the complex equations did nOl result in a s¡gníficantly hígher R" than the simple equations shown ahoye.

Discussion Spr.ly treatments

Crop grol\th und disease

The objective of lhe spray treatments was not disease control per se, but ¡he generation of epidemics al different severity levels, Ihis objective was uttained. Oxycarboxin has no direct elfecl on ¡he physiology "fthe hasl plant lNewby and Tweedy, 1973; Pring and Richmond. 1976), Spray treatments inftuenced rust intensity. and therewith, indírectly leaf area índex. The magnítude of dfects varied with !ocation, cultivar, canopy layer and parameter. Spray effects on other diseases and dead tls5ue were negHgjble,

Leaf Mea index wus most affected alter pod formatíon, Rus!. measured by either incidence. severity, pustule density or pllS~ tule sÍze. varied with spray frequendes. Incidence was found most sensüive since differences were sIgnificant at ail growth stages. whereas the impact of spraying 00 severity and pustule den:;it:: ,'as larger after flowering than duríng vegetative devd­opment,

DitT'erences between cultivars were common for LAL inc¡~ dence. severity, and pustule density but not for pus rule size. Rust epidemks began at an early stage. and the bean crop continu~d to produce new ¡caves. henee ir is not $urprísing tú

see great differences between treatrnents for incidence froro an eady developmental stage onward as opposed to rust severity and pusmie density. Spray treatments produced the highest vanations at pod inítiation and secd tilling. regardless of the paramders assessed,

In mo~t Cases (LAI. incidence, severity, pustule dens1ty), there is a strcng cultivar by treatment {C*T) intcT,-lCÜOn, stronger ¡n SUS than in RES. suggesting a differenrial reaction to ;ust intensüy at different levels ol' (partlal) resistance, This IS no{ uncomn:on as Lirn and Guunt (986) suggested for the spnng

RUSled P¡'uwohn B::an'> in Eth¡op¡,¡

Tahlc -: Correlallon matw.:c:<' o;'pod .. per plant \ PPl. seed:. pe: pod (SP) sed we:g:ht tSW} and seed ) ¡eld (SYl - --.. ~.--_._- .. __ ._.~

--.~~~-._-~ .. __ ._~,.~ .... ~-----~.----.-- --_.~--

Year LOC,lt¡O;¡ CulIhar pp SP S\\' Sy ~~-_.~ ------- .. _--_ .. ,,-- .-----~'_--

pp 1990 Amb0 SUS 1.HO

sr e,51~ 1,00 SW fU" n:: LOO sy 0.90 fLj4 0,Sr; LOO

pr RES 100 sr ti» 1.00 SW 0.46 m LOO SY 0.81 ns G.3-8 LOO

pp 1991 Dcbre ZClt SUS 100 SP 0.56 100 SW 0.69 ns LOO SY 0.71 0.48 0.51 100

"number úf piN), 10 te),! correlatlon = ~O 1) trcannent\ by 6 rcpiJcotlOmL bm = no! ~igniñtdm: r value ~ 0.36 s!gmficunr ai P % 0.05.

bar1ey~leaf rust pathosYSlcm. The result suppons the s.uggestíon to combine partía! resistance wíth adequate fungicide man~ agemem (Zadoks. 1989, 1993). bu! for bean production m Ethi­opía one has to be caulíous in fo!"commending fungicides, The comp011ents uf disease management bcyond partíal resistance are probabiy cultural (intercropping, c:ulti\ar mixtures. sowlng datest

Caoopy tll.'.-m

Distinctlon bel\\cen leaf layers produced mteresti11g resuits. The lower leu\cs díed early. Treatment effects at the lower canúp~ layer \\ere not as sIrong as in the upper canopy and middle canop) iayers. but rcmained significant in most cases. Cultivar by trettment ínieraction was absent at the !O\\er can­opy ¡ayer mainb due to lae!.. of differences between cultivar:;, Rust began to develop on the lower canopy layer and increásed and moved up.wards as the crop developed, Rust intensity seemed te decline at the lower layer because 01' remova! (Zadoks and Schem. 1979) by dealh úf primary pustule!l a11d subsequent appearance of many bu1 slgnifkantly smaHer pustules.

MoreoveL ¡caves at Jower canopy ¡ayer senesced and dropped ear!y. Effects of early epidernics on lower leaves were reported by Rouse el al. (1980), Kolbe (1982) aud by Lim and Gaulll (1986). In legumes. it is not always clear which nades contribute moS! to yield (Waóill el aJ.. 1984: Debouck, 1991). RuS! in Phaseoius beans. if it comes early. wilJ most often affect the primal}' and the first trifolioiate ¡eaves which later become the lower ¡eaves, The fac! rhat rust was finH observed in the lower leaves make these leaves epídemiologic-ally importanC despitC' low incidence and eady removal frÓI11 the infectiQn process. This is of particular imponance to any rust control strategy. The ioss of leaves in the lower canopy layer per se may not airoct ~ íeld significa11tly but infectiú11 at thi!> stage acts a., a source of inoculurn for the upper canopy laycrs. suggesting the appropnateness of managing bean rust al this early stagc"

Vit'1d t(im'jJ6MIl1S

Yield depends on climate, production situatiofl. cultivar, patho~ gen and disease severity {Zadoks and Schein. 1979; Daamen. 1989; Savary and Zadoks, 1992a,bl. Analysís of dísease effeelS on yjeld should include analysis of yield components lO obtain

a balanced \"ie ... ' of theu' cffccts on final yield and th-elf relation~ ships. Sorne- 01' these yieJd components were studíed in the present repon

Epidemici. affected seed yield. seed weighi. seeds ¡:'Ier poo and pods pet plan!. There was variation in the degree of response (Fig, 4), as secd yield and rods per plant werc more affected than seeds per pod and seed weight. SUS was always more sensitive to spray treatment than RES. suggesting a Jarger efft:ct of spray s in susceptible cultivan;.

Disease effecls 011 legumes incJude reduC"uon of attainable nurnber of piant~. pods per planto seeds per pod, seed weight and !.leed yield The effects 011 the yield component~ and seed yleld depend on tbe pathosyslem, Viilliams (l975, 1978) and Rapwood et.al. (1984) shO\-ved tha~ rus! (Ur(mlyce.\ !'Icia-lahü(')

of faba bean mainl) affected seed \veight and chocolate spot ¡Botryli., fahad rn~-l.mly pods per plant. In our study poos per plant was moSi affected.

The present repon suggest:. the importance of rust in coru­mon bean. especialJy when á susceptible cultivar is attacked early. Rust is endemic in Ethiopia, especially Jn the Rift Valley and the soutnem provinces. where an outbreak of rU5t in com­binaríon w1t11 wlde~spread cuhivation of a susceptible cultIVar can be devastaüng_ Tbe yield advantage obtained byapp}ying fungicides frequendy shows the damage potential of bean rust. but the experimental results also indicate that even minimum chemical treatment could produce economic beneflts. The use of fungicides in Ethlopia is infiuenced by the availability and cost úf chemicak availabihty of sprayers and water, and the value of the crop (cash or consumption)"

Relationsbips

Rust MSeSSmen1 parame1ers

Smce distase assessment is laborious. bean breeders and exten~ sion specialists want a simple method suitíng their needs. Cor­relations between tbe rust parameters incidence. sevcntv. pustule density ami pustule size depended on cultivar. iocati~n and leaflayer. Higher correlatiou coeffidents were obtained for susceptible than for partially resistant cuhivars, and r values. were better al Ambo. where disease pressure was higher than at·Debre ZeiL Linear correlations become more significant with larger ran,gcs of rust intenslties.

400

Ambo. 1990 SUS

§ lO.

~ " S

1l ro >

• ~ ;; ~

Ambo. 1990 RES

=, =,

_.

=, ~ '00 =, o

,,1 & s -, J:! 5O~

_. • >

• 25é ~

~ SV SW SI' .. Y'eld parameters

Fu:.i. Yldci comp0:lents in relative v;¡iues, Yield values ilS percent of th; referencc frust free pior). (A) Ambo, 1990 SUS. (B) Ambo, 1990 RES; {C) Debre Zeit. 1991 SUS. SY seed yield; SW = seed weight: sr .'" number ol' seeds pod- 1

: PP = number of pods p(¡lnl- I Columns per llcm r:.:prcscnt spray frequency from O (untreated t:onrrol) to -4 trCU\rnents

Thefe are conftic:ing reports on relauonships of incídence and severity. The lnCldence-severlty relatlonship may vary with season and leaf ¡ayer (James and Shih. 1973). wíth location but no! with season (Chuang and Jeger, 1987). and with environ­mental factors {lmhoff et al., 1982). At h1gh <Jiscase !evels. the relationship between incidence and severity becomes undefined (Zadoks, 1985). The relarlonship bet\veen rust assessrnent par­an1eters is extremely variable. A choice has tú be made ac.'Cord­ing to objectlves. For bean breeders, rus[ seventy may be more attractive, For epidemiological purposes. rust seventy and pus­tule Jensüy are more appropriate, EXlension specialists. \-I"ho may have to deal wtth several erap::; and wilh discases and ¡n~ects simultaneously, muy wish te sel~t lhe :;implest (incl­dence). WhlCh muy be less accurate ror evuluating beun rus!.

Le.,! ;lrtu iodex aOO }idd ('OOlponents

LAl is <Jn important detenninant of seed yield in the cornmon belln. LA! was more dosel)' related to pods per plant than to

HABTU and ZADOKS

seed weíght and seeds per podo The correlations between LAI­pods per plant and LAJ-seed yield varied Wilh growth stage rather than with cultivar and location. The r values were larger al the later stages of erop development. This is understandable as differences in LAI between treatments were greatest after pod fonnation. The r valt:.es for LAI-seeds per pod and LAJ~ seed weight depended on locaLÍon and cultivar.

Rust aOO yield parameters

Correlations between rust and yield parameters \vere affected by cultivars, growth stages. canopy layen; and !ocatÍons. ~o dear trend was visible. Relatiouships oi rust parumeters wüh seed yield or pods per plant were always beuer tban with seed we.ght or seed per podo especially ror SUS at Ambo. The relationships INere not greatly affected by the development of the crop but varied with iocatiou. The strong relationship for seed yield and pods per piant at all growth stages and canopy layers regardless of the :-ust parameter used. suggests- the importance of aH stages and canopy ~a}eiS in aoy further epj­demio'ogical studics, Tne poi m will be daborated in a sub~ sequent papeL

Vield compmwuts

In dry be;!!]S the principal components of yield are pods pe!" plum, seed:; per pod. and seed welght (Adame;. 1967). Our data suggest a strong correlatlOn betv..'een pods per plant and seed yield. Early attack by rust mal' have atfccted the number 01' fl.owers. Be,lO rust <1t an ear1y stage atfects growth and devei­opment otll!aves and thus [he production oftlowers and finally. the pod number. The effect of r:lst on abortiun ~md pod fi/ling could be partly due to the s,hortening of the pod-fiHing penad by defoHaüon, The !mg:gestlon úfStone :.md Pedlgo (1974). thar the pod filling stag:e was the most sensiuve to defoIJation :.md subsequent IOS5 uf photosynthesis, explams the slrong relation­ship between pods per plant and seed Yleld" The strong COf­relation between pods per plant and seed y¡eld under different condítions (Ioc:.nion. cuiti\·ar and growth stagesJ ¡!lustrares the overriding importance of rust attack ,tt an early stage and its subsequent influenc~ un the number 01' ftowers.

Ackno"ledgements

The aUlÍ10rs thank the Holena Agnculnln)! Rc>c;.:rcn CC'::tC'T <lnu the Plant Prútecuon Research Centre al Ambo {or pro\ l!.hng field lacilitH::'. Thanks also to AbyH! Tílahun. Y¡¡Ola Abenv and Tesla:c Beshlf rúf áss¡stance m Jata collecilon J.nd (o Wond¡magege f{)r manilgernent 01 {he tria! at Debre Zeit Financ¡aÍ mpport wu~ pw\'ujed by Wagemngen Agrleulturál Un¡vers¡ty. Tht' '\e!herlands. InSllIute of Agricultural Research. Erhwp¡!L and CIAT <!aStcrn Afce;. reg¡'.)l1.¡! otfke,

Literature Adams. M, W, i 1967): Bu5IS of )'wld cúmponcnt5 in ~'rop p!UJ1ts wJth

~peclu! refcrence to the fidd bean. P¡WW:O/IIS ruJqarn Crop Se!. ¡, 505-510,

Chuanc. T. y , M. J. Jc!!er.l; 9:\7): Rdaüüll!>.ll1p bet>"ccn ::;c¡dence ;;.nd scve;üy 01' banur..¡ 1;,U· Sp:,lt in TaiwalL PhYlopathoicgy 77, 1537--1541.

Oaamen. R. A. II%q)· ,\-..i\c)q;,ent oI' ¡he pwllle nf pü\\dery mlldew ,md il!> damage funCHon al !ow d¡scaSl: imenslllcs in tieid C.\pí . .'nmenh '-'Illt wmter wheaL Nelh, J. Plan! PathoL 95,1\.5-10"5.

Deb0w:L D (199l): Sy,,:;;rllUIh.':i .1nd Mürphúh.'!,!y_ In- \llll Schüüho\c!i A __ ¡¡nd O. VOYSCH ,ed!>..i. Common l>édIH: RC$c!I:'Cll for cop Improvemem, pp. 55 118: C.--\.B lr11ern,won..¡1. L'K.

De Wic e T. (l9K2): L<1 productlvtte des paturages ~ahéliens. In: Penmng de Vries, E W T ,md M, A, DJite)c (eds,l. La Prouuctmte des púturag:es sahélien~--L ne étude des )01s. d¡;,s l¡ég¿'tutH.ms, de

Rusted Plraseolus Bcans in

l"exploitation de cette ressource naturetic pp, 23~35, Pudoc Wag­eningen.

Fernadez, F" P. Gepts. M. Lopez (1986); Etapes de desarrollo de la plantarle frijol comuo (Phaseolus rulgaris L,_ CIA T. Calí. Colombia 34 pp.

Free<!, R. D .. E. J. Heflin, S. P E,,,,mmith (1986) MSTAT 1.41. Michigan State Umversíty.

Habtu A., K. Awgechew (19S4); Chemical control of bean anthracnose in haricót bean, Ethiop. J. Agric, Sd. ti, 78--87.

Howland. A, K, J. C. McCanncy (1966); East Afrlcan bean fust slud­jes. East African Agrk For. J. 32.208-211),

lAR, Institute of Agricultura] Research (19741: Lowland pulses pro· gress report for [he penad 1974. lnstHute of Agricultural Research, Addis Ababa, EthlOpia,

Imhoff, M. W., K j, Leonan!. e E. Mam (l982): Analysis of disease progress curves. graóients, aod mcidence sevcrity relationships for tield and phytotron bean rust epide-mics. Phytopathology 72. 72~80.

James. W. e, c. S. Sh.ih (1973): Relationship between íncidence and severity of powdery mildew and lcaf rust 011 wmter wheaL Phy­topathology 63: 183-181.

Kolbe, W. (1982): Zehn Jahre Versuche mlt Bayleton zur Mehitau~ bekampfung im Getreide·bau (1972-1981). Pfianzenscbutz nach­ricbten Bayer 35. 36-71.

Lim. L G" R, E. Gaunt (1986): The effect ofpo\vdery mildew íErysiphe graminis esp. hordei) and leaf rust (Puccinía IlOrd!'!) on spring barley in New Zcaland. 1. Epldemic development, grecn leaf area and yield, Plant Patho!. 35, 44-53.

Mackenzie. D. R. (983): Toward tlle management of crop losses. Jn: Kornmedahl, T. and p, H. Wmiams (eds.J. Challenging Problems in Pian! Health, pp, 82-92, American Phytopathological Society, St. Pao!. MN, eSA.

Newby. L e, B. G. Tweedy (1973l: Theeffect ofoxycarboxin on amino aCld metabolism by PhaseQlllS l'ulgaris var. Pinto_ Phytopathology 63,68&-688.

Pring, R. L D. V. Rlchmond (1976): An ultrastructural stud:y oC the ctrecl of ox.ycarboxin on Urom.vces p/wseoliinCecting [eaves of Phase-01«5 rulgartS. Physíological Plant PathQl. 8: 15~162.

Rapwood. O, R. A. Bainbridge. J. McEwen, D, p, Yeomao (1984): An etTcct ofrust íUr-omyres tida-fabae) on the j'ield of spring-sown field beans (Vicia/aba) io the VK. erol' Protection 3,193-198.

40,

Rouse, D. L L. V. Gregory, J. E Ayers. H. Cole (1980): Powdery mlldew of wheat: Relallon of y:¡eld camponenrs to díscase severity. Can. J Plant PathoL 2, 131~136.

Savary, S .. J. C. Zadoks 0992a): Analysis of erap loss io the mulrjple pathosystem groundnut-rust-Iate Jeaf spot. L Six Experimcnls. Crop Protcctton 11; 99-109.

Savary, S .. J, C. Zadoks (l992b): Analysis of crop 10$5 in the multiple pathosystcm groundnuHust-late leaf spoc H. Study of the inter­actions between d¡sealies and crop intensificatian in factorial expcrt~ ments. Crop Protecilon H, 110-120.

Sbgh, J. P .. A B. K. Musiyimi (1981): EffecL<¡ of heao rust on bean yíeld. Indla.n J. PhytopathoL 34. 37g-379,

Sla\'cly, J. R .. G. F. Freytag, J. R, Steadrnan. H, F, Schwaru (l9&3): The 1983 bean rust workshop. Annua! report o[ bcan Jmprovement cooperative 26, 4-··ti

Stone, J. D .. L P. Pedigo (1974): Development and economic injury leve! ofthe green cJover-wonn on soybean in lowa. J. Econ, Ene 65, 1 97-2D1

WadiU, \ .. K Pohronezny, R. McSorley, R H. Bryon (t984): Effecl oí' manual defoliation on püle bean y¡eld. j, Econ. EnL 77. lOl9-1023.

WiUiams. P. f. (1975): Growth of broad beans infecled by Borrytis !aboe. J. Han. Sei, SO. 415---424.

WiUiams. p, E 0978): Growth 01' broad beans mfected by Uromyces rióo-{abac. Ann. AppL BioL 90. 329-334.

Zadob, J C (1978): Methodology of epidemiologlcal research. In: HorsfalL J. G, ami E. B. CowIing (eds), Plant Disease: AnAdvanced Treatise. pp. 63-96. Academic Press. New York.

ZadoKs. J. e (1985): On the conceptual basís of crop ioss assessment: The thrcshold theory. Ann, Rev. PhytopathoL 23, 455-473,

Zadoks, J. C. 0989J. EPIPRE. a computer based decision support system fo! pest and ó¡sease controlln wheat: IlS development and implememation in Europe. Plant Dis. Epidemiol. 2, 3--29.

Zadóks, J. C. (1993): The partial past: Conunents on the histar)' of thinkmg about resistance ofplants agaiost insect:s., nematodes. fungl, and otner harmful agents, In: Jacobs. Th. and J. E. Parlevliet {ros) Durability of Discase Resistance, pp, 11--22. Kluwer Academjc Pub­lishers, Dordrecht, The Nethedands.

Zadoks. 1. C, R. D, Schein (1979): Epidemiology and plant disease managemenL Oxford University Press, New York. 427 pp,

Euph)'llca 83: 95-102,1995. 95 © 1995 Kluwer A~"fldenllc Publt .... hers, Prínted /11 tite Ncrherland.'1

Components of partial resistance in phaseolus beans against an Ethiopian isolate of bean rust

A. Habtu 1.2 & 1. C. Zadoks I

J Departmelll of Phytopathology. Wageningell Agricultural Universit,l. PO.BoJ. 8025. 6700 EE Wageningen. The Netherlands; 2Perll10llem address: Imtituleof Agricullllral Research. Nawrerh Research Centre. P.O.Box 436. Natareth. Ethiopia

Received 15 Juiy 1995. accepted 10 February 1995

Key woros: bean rust. common benn. Phaseolus l'ulgaris, Uromyces appendiculatus. infection efficiency, infectlous period. latent period, parlial resistance, pustule sÍze, sporu1ation cnpacity

Abstract

Phaseolus bean cultivars. obtained from the Ethiopian national breeding programme. and cultivars widely grown in the country, 15 in total, were tesred in a greenhouse for five components of partial resjscance lo one ¡solate of boan rust. The single-pustule ¡solate carne from Ambo. a site where bean lines are tested against rus! because the climate is conducive to bean rust. The components examined inelude laten! pedod (LPso), infcetian efficiency (lE). sporulatíon capacíty (SC), infcelious period (IP) and pustule size (PS). Differences in cultivar responses were found for all PR components. Differenees were largest. however, for ¡nfeetion efficiency and sporulation capacity. Cultivars Exrico 23. A 176. Veracruz 10 and BAT 1198 had a high level of PR 10 the isolate tested. Mexícan 142. a widel)' grown cultivar in Ethiopia was intermediate, whereas Red Wolaita. an important cultivar in che south, showed a low level of PR. Linear correlations between LPso anó lE. and between se and PS were high. Linear correlarions between lE. se. or PS ",ith IP were not significant. Though differences in cullivar response were found fm all components. any one parameter may nOl suffiee lO explain the PR potential of a particular cultivar. The study suggests that latent periodo infection efficiency and pustule size should be used in seJection for PR. For the evaluation of large numbers of bean cuhívars in the greenhouse j lE and PS are preferable to minimize labour requirements.

Introduction

CommOD beans (Phaseolus vulgaris L.) differ widely in their susceptibility to bean rust (Ballentyne. 1978; Coyne aDd Sehusten, 1975; Fromme and Wingard, 1921). Genetic studies in beans have suggesled most rust resistance to be monogeníc (Ch"st and Groth. 1982; GraflOn et al .• 1985; Stavely. 1984, Webster and Ainsworth, 1988; Zaumeyer and Harter, 1941). Because of lhe ability of the bean rust fungus to adapt to new bean cuhlvars with monogenic resistance (high variability in terms of pathogenicily). theeffectiveness of race-specific resistance is only temporary (Beebe and Pastor Corrales. 1991). Attention therefore shifled tu a raee non-specific type of resistance, partía) resis­tance. Partial resistance (PR), a resistance that causes

a reduced epidemic build-up of a pathogen despile a susceptible ¡nfection lype (Parlevliet, 1981), can be expressed at different phases during the life cycle of a pathogen (Zadoks and Sehein. 1979).

Simulated epidemies and experimental investiga­tions suggest latent period lo be the most important component of partial resistance in determining the rate of epidemic build-up (Parlevliet and van Ommeren, 1975; Zadoks. 1972). ¡nfection frequency. ,poroJa­tion capacity, pustule size and sporulation pedod were aiso used as estimates of partial resistance in sever­al pathosystems (Mehta and Zadoks, J970; Parlevliet. 1975; Parlevlíet and Kuiper. 1977; Shaner and Hess, 1978; St.tler and Parlevliet, 1987). In the bean-rust pathosystem (Statler and McVey. 1987), no differenees in laten! period between cultivars were found. bUl the

96

number uf pustules per uní! area and the number of spores per pustule were associated wíth levels of par­tíal resístance.

For a variable pathogen, in lenns of pathogenici­ty. such as Uromyces appendiculatus (Pers.) Vng. of beaos. seleclÍon for higher leveIs of PR migh! be a good altemative to setection for specific resistance. at least when PR ís not race-specific andlor monogenic (Turkeosteeo. 1973). Selection for PR is not always easy because the expression of PR varies according to environmenlal faetors (Zadoks and Sehein, 1979). For a better unders!anding of !he interactions between hoS! and palhogen it is essential <O evaluate compo­nen!, of PR. For applíeation in a breeding prograrnme one or two of the components have to be seleeted. In the bean-rust pathosystem this paper addresses the fol­lowing: whieh components should be used for disense screening prograrnmes and can we detect djfferences in the level of resistance among bean cultivars found in the advanced stages of the breeding programme with respect to the components of pardal resistance and, if so. which eomponent(s) is (are) the most effeetive and l'eliable in deterrniníng PR of rust in benos?

Materlals and rnethods

Experimemal design

The fitieen bean cultivars used for this experiment orig­inated fram the bean impravement programme of the lnstitute af Agricultural Researen. Nazareth, Ethiopia, of which Red Wolaita and Mexican 142 are widely­grown cultivars, Exrieo 23 (Awash) and A 176 (Roba) were recently released and Brown Speckled is a stan­dard check in !he large kidney bean trial. Bean plunts were grown in a sterilized soj) (sandy loam 50B rep~ resenting the soil type in the Rift Valley) in 15 cm diameter pots in the greenhouse al the Nazareth Agri­cultural Researeh Centre. The planlS were grown al 'Ibout 23 '" 3 'C dUlÍng day time and 15 ± 3 ·C at night. As the experiment was conducted in the dry sea­son, light \Vas not a limiríng factor. No fertilizer was applied.

Two separate experiments were carried out. one for determining latent periodo infection effidency and pustule size. and the alher for delermining sporulation capacity ano infectious periodo Each experiment was performed three tímes in sequence {blocks), each time wlth four replicntions (subblocks). Per subblock. each cu i ti var was represented by onc poto four pi ants per pot,

and pots were ranctomized within subblocks. Assess­ments were made 00 two ofthe four plants. two leaves per plant

Inoculation

Al! cultivars were inoculated with urediniospores of a single-pustule isolate at lhe primary lcaf stage, 10-12 days after sowing. The iso)ate originated from Ambo, where the relatively cool and moist clirnate ís conduclve to bean rusto Inoculation was carried out by spraying suspensions with about 2 x 10· urediniospores ml- I over both sides of the primary bean leaves. Microscope slides greased slightly with Vaseline™ were placed horizontally near the plants lo check the resulting 'pare densíty (spores cm-2 ). After inoeulation, all plaot' were placed in a near-saturated almospnere. Twenty-four hour, after Ibe deposition of spores, planl' were returned to a bonen in the green­nouse where they remained for the duration nI' lhe experiment.

Progress curve

Numbers al' pustules per cultivar were caunted daily once white ftecks hud beeo observed. The change in number of pustules with time WQS pIotted to see varia­fion arnong cultivars,

Larem periad and infection eJjideflcy

The lateot periods were calculaled by counting the number of visible pustules every day until no more PUS!ules appeared fParlevliet, 1975). Latent pedod, LPso, was calculated as the time in days berween inoc­uiation and lhe moment at which 50% pustules were open. The infectioo efficieocy (lE), the ratio between Ihe Dumber of resulting pustules and the number of spores applied. both per unit area (Zadoks and Scheio. 1979), was determined by couoting the oumber uf pus­tules per unit leaf urea (sum of the upper and lower surfaees) oftne leaves about 15 days uf ter inoculatíoo. For both parameters counts were ~ade on 2 x 2 cm2

area.

Sporu[atioll capadt)' and infectious period

Sporulation capacity (Se, weight of spores produced per unit area) and infectious period (IP, period in days fmm the appearonce of the ¡¡rst ope" pustule ""ti] the end of sporulation) were determined per cultivar.

97

Tabie 1" Latent pcnod (LPs¡,), micelion efficiency (lE), xporulationcopac-ity (se), lnfectlous ptnod {IP) ano pU~lule ~il,.e {PS) of primary leaves of 14 cllttivars, inocul:t,e-d with a bean ru.~t i~olale from Ambo

Culrivars LP<)j; lE SC IP PS

ICA 15441 9A:l 2.5ú O.34cf 27.6a 4.0c Jalisco 33 9,6 .. ),lbcd Ll2a 14.6d 6.0. RedWolaitu 9.6n 3.5bc 0.76cd 15.2d 5.0b

Brown SpeckJed 9.7n 3.% Q,38ef 15.2d 5.0b KV Womk:r765 9.7a 5.4a O.44de 24.3b 5,Ob

Diacol Cnlima 9.9;)0 2.4d 0.58cd 27.3. 4,Oc

Mexlc;)11142 g,9ab 2.9cd O.53de 23.6b Bcd US#3 9,9.b 3Abc 0,50de 21.5bc 3"scd

Mexlco 6 IO.lnb 2.4d O.5Jde 21.5bc 4,00

CSw IO.2ab 3.6bc Q,47de 15,5d 3,5cd

BAT 1198 10.7.b 0.8ef Q,Q4g 19.& 2.5c

Veracruz: 10 1 L4b L2e O.19fg 22.4b 3.0de

Exrico 23 (Awa;;h, 17.0c O.2f O.D4g 144d 2.5e A 176 (Rob.) 18,6, O.lf O,D4g 15,Od 2.5e

Cultivar meam; withm cach componen! followed by Ihe same _euer are not ~ign¡ñcantlyd¡ffereO! al p:S 0,05,

Spores were colleeted evety 3 days (until no more spotulation occurred) by means of a spore collector, beginning the first day of sporulation, Spores wete eol­locted from two areas of 4 cm', one at either side ofthe leaf. The data were converted ro mg spores cm- 2.

Pus!ule size

Pustule sire (PS) was assessed when itreached its max­imum. at abou! 14days after inoculation formost ofthe cultivars, according to the scale of Stavely el al., 1983 (1 = no visible symptoms, 2 = necrotie spots without sporulation, 3 :diameter of sporulating pustule < 300 ¡.tm,4 = 3(){}-500 JLm, 5 = 500-800 JLm and 6 " ;> 800 ¡.tmJ.

Statistical analysis

AII data were subjected to ANOVA and mean values were separated by LSD al p ~ 0.05,

Results

Data compaction

Each experimenl was performed 3 times sequential­Iy (blocks), with 4 replications (subblocksJ per time,

Since no significant differences were found between blocks and subblocks, data were averaged over repli­cations and times,

Progress curves lar pustule production

In sorne eultivars minute, mised, white tlecks appeared on bOlh sídes of the leaves abou! 7 10 8 days after inoc­ulation, A day or two later the epidermis ruptured and reddish brown coloured sporulatingpustules appeared, AII cultivars showed asymptotically sigmoidal curves (Fig, 1), except BAT 338-Jc which was immu"e to the Ambo isolate. In most cultivars a maximum was reached asymptotieally 15 days after inoculation but about 24 days for Exrico 23 and A 176, The cultivar, can be grouped, ex post Jacto, ioto four cJasses. Group 1 is represented by KY Wonder 765, group 2 by Brown speckled, Red Wolaita and Mexican 142, group 3 by Veracruz !O, and group 4 by Exrico 23, The olher lines are nol shown to avoid blurring Ihe pieture.

Latem penad

LPso, varied between 9,4days farICA 15441 and 18,6 days for A 176 (Table 1 J, The eultivars can be grouped into 3 LP5(J e1asse, (Fig, 2), Mostcultivars are in group l with latenl periods ranging from 9,4 to 9,9 days. In group 2 are Mexico 6, CSW, BAT 1198 and Veracruz

98

E u

'-GJ JJ ¡:: 5 Z

40r-----------------------~--,

8 10 12 14 16

Days afrer !noc~ie.tiOfÍ

--1- KY Worder765

- -fr - 8rown SpeCK,

--- Red Wcla:ta

__ o Veracruz 1C

-+- Exr;co ::3

Hg. 1. ProgresHurves of numberof pustules crn-2 with lime io da;;s for 6 reprc¡;CntatlVc cultiVUcs" pnffi<l.ry kilves.

'" > 1\)

ID o:

1,00 I----~~~------, ~:;..rv'

0.75

0.50

p:: / SJ'

/;'/9 ,/?' /: . I

jI ... ' I i. ,,' ,

JI i ,i Iv / l / i , i l' !

0,25 ".

I /

/ ¡

/

/ +' /

,-

/ ,/

V/~~ / 0.00 ~";;';~.~ __ '/ ________ --J

8 12 14 16 18

--r-- KY Wonder765

- _\7-- - 8rown Speck.

'l. . h/exlcan 1.4 2

-11-- VeraCrU2 ~ O

FI}; 2, Rclative numrn:r of pu»tul!:s per cultivar ploltcd wilh lime ltl ..layo; j\Jr Jelcrminnllon (Jf latenl flCnód l LP'ill)¡ grJ.pn \howmg su rcpresenlativc r.:ultivars,

Tnble 2. Correluuon mu!nx of laten! period (LPstl ), infeclion eftk:lency (lE). sporuJatiQn capacity (Se), infe<::t!ou:;; penod (lP) nnd pustule size (PS). Num· ber uf observation;;; ffable 1) = J 4. P S 0.05. Entries are. linellf correlation coefficlems

LP50 lE se IP

lE -0.74

se -0.62 OJS2

IP -!lA3 "' n:;.

PS -0.62 0.77 0"85 n,

10 with ao LPso betweeo 10.1 aod J 1.4 day •. In group 3 are A 176 aod Exrico 23 with an LP50 of 17.0or more

doys.

lrifection efficiency

lE varied between 0.1% for A 176 to 5.4% for KY Wonder 765 (Table l). lE was below 1 % for A 176, BAT 1198 and Exrico 23, belween I and 2% for Ver­acruz 10,2-3% for 4 cultivars and greater than 3% for tbe rcmainder Differences in lE were mainly due to tbe .mall number. ofpuslules observed io A 176, BAT 1198 and Exrico 23.

Sporularian Capadl}

Total amount of spores produced during one infe<:­tÍon cyele varied between 0,04 mg cm- 2 for A 176 to Ll2 rng cm-2 for Jalisco 33 (Table 1). Total amount 01 spores produced was high for Jalisco 33 and Red Wolaita, moderate for Mexican 142, Diacol Calima .nd Mexico 6, and low for A 176, Exrico 23 and BAT 1198.

¡n'cc/ious period

lnfectious period varied considerably (Table 1). Six varieties had a short IP in the range 14-16 days, where­as Ihe remainder had 20 days or more. The longes! IPs (2: 27 days) were found with Diacol Calima aud ICA 15441.

99

Pustule size

Pustule size. classified in micrometers, shows variation bClween cultivars (Table 1). Pustule sizcs werc small

3.0 11m) for cultivars A 176, BAT 1198, Exrico 23 and Vera Cruz lO, small-medium (3.1-4.0 11m) for ICA 15441, CSW, Mexican 142, Mexico6 aod US # 3, large (4.1-5.0 11m) for Brown spe<:kled, KY 765 and Red Wolaita, and very large (> 5.0 1,m) for Jalisco 33.

Relationships between the pr components

AII paired correlatíons (Table 2) between LP, lE, SC and PS were sígníficant and relatívely high. Howev­cr, correlations of IP with tbese parameters were not significan! with the single exceplion of IP with LP

Discussion

Contexl

Partía! resistance is usualJy supposed to be polygenic, manageable by breeders, and durable (e.l'. Lamberti et aL 1983; Jacobs and Parlevliel, 1992). In sorne cases, however, PR is monogenic (Turkensteen, 1973) and thus líable to be overcome by a new and adapted phys­iologic race. The genetíc background of the resistance in the varieties tested bere is not known. When grown widely, sorne liues such as Exrico 23 and A 176 could possibly exert such a high selection prossure on !he rust that new and adapted races might appear. Sele<:­tion for the highest possible partía] resistance could be risky.

The experiments reported were desigued to repre­sent Ethiopian couditions. An array of varietios, used in the Ethiopian breeding prograrnme, was lested. The widely grown cultivars Mexican 142 and Red Wolai­ta were inc1uded for comparison. Due to constraints imposed by technical, financia] and polítical factors only one rust isolate could be tested. Though it carne from Ambo, the brceders' testing site for rusl resis­tance. its representativeness cannot be guaranteed. In faet, unpublished results sugge't tha! the Ethiopian bean rust population j5 rather diverse. No fertilizer was applied as it is not recommended for beaos. The soil type (sandy loam) used represents ¡he soils of the bean growing arca in the Rift Valley.

The experiment was monocycHc, testing young plants in a greenhouse with a single isolate, at low soil

100

fertility leveL Thus. ils result. cannot be generalized. Rather. they should be eonsidered as a methodologieal excereíse. in the wake ofthe pioneer study by Fromme ano Wingard published in 192 L

Variarions in components

Latent period, infeetion efficieney. sporulation capac­ity, infectious period and pustule size are impor~

mm components of partial resistanee, Zadoks (1972) demonstrated The importanee oflatent period by mean s of dynamlc sjmuiution. In experiments. latent peri­od was found to be an important component in some pathosystems (Parlevliet. 1975; Neervoort and Par­levliet. 1978; Savary el aL, 1988), among whleh the bean rust pathosystem (Fromme and Wingard. 1921: 10-15 days), In other pathosystems (Statlcr and McVey, 1987; Roumen, 1993) no important dif­ferences ín LP \Vere found, among which bean-rust (Statler and ;-leVey, 1987), In the 15 cultivan; of beans studied here. Importunt differences in latent period were round. The differences were largely due to two cultivars, A 1 í6 anó Exrico 23, Wilh lateOl periods cxceeding 16 days. The difference between groups l and 2 ;s roughly one day, If the beun season is 90 days and the rust season is 80 days (primary leaf infected), the rustean cmnplete 8cycles Ingroup I and 7 eycles in group 2. with multlplicationsup to lO· and 101

, respec­tively. The use of a partially-resistantcuHivar in un area of origin could play an important role in reducing the amouot of rust inoculum migrating to other pans of the country, Exnco 23 and A 176, in group 3. are newly reJeased culti\'ars testcd under a wide range of enviro n­mental conditions in Ethiopia. Despite their suscepti­~ility ro anthracnose (Habtu, unpublished), limiting wider ,cceptanee, they showed a high level of partia! resistance to benn rust at aH test sites. Collaborativc actíviúes, either in the area of regional rust nurseries or beao yícld regíonal trials. eurrentty ongoing in East­em Afríea. <hould help 10 determine the performance ofthese CUltiY:lfS under varying dimatic conditions.

Differences in infection efficiency among cultjvurs were found in most parhosystems stuJied (Groth and Urs, 1982; Aho and Ou, 1982; Parlev!iet and Kuiper. 1976; Statler and McVey, 1987; Roumen, 1993), Our s[udy also supports such findings. Sporulationcapacity was llighly correlated with partial resistanee in the field (AUST et aL 1984; Neervoort and Parlevliet, 1977), SmaU pustuk size was assocíated with s)ow rusting oí' whem (Ohm and Soancr. 1976) and hlgh partia! resis­tanee '" beaos (Stmler and Me Vey, 1987), In Qur study

cultivars A 176 and Exrico 23, with long latem periods, low infectíon effidencies and iow sporulation capaci­ties had smal1 pustules. BAr 1198 and Vera Cruz !O had somewhat shorter latent perlods but were otherw;se similar,

This s!Udy has indicated wide differenees between cultivars in five components of partía) resistance. Ideal­Iy, a hlgh degree of resistance ¡mplies long latent peri­od, Jow infeelÍon efficiency, low sporulating capacity. short infectious pedod and small pustule size. Exrico 23 and A 176 seem to possess such ideal charaeter­isties, elosely followed by BAT 1198 and Vera Cruz 10,

ConverseIy, a highly susceptible cultivar will have a short Iatent pedod, high infectlon effic;ency. high sporulation capacity, long infectious period and large pustule SilO. Of the 15 cultivars tested none showed such characteristics. Mexican 142. the wideJy grown cultivar, showed a moderate infection efficiency. Red Wolaita, the most dominant cultivar in southem Ethiopia, showed a high infeetion efficieney, Note that Mexican 142 is in lhe higher intermediate category if a11 components are eonsidered, In a crop loss study (Habtu and Zadoks. 1995), where Mexican 142 was used as a susceptible check, a seed yield 105S of up to 85% was obtained, This difference could be due to a high damage potenlial expressed by Mexican 142, One cultivar eould be more susceptible to damage than another.

Correlation of componenls

The rclationships berween the componenrs are not eonsidered to be high, 0,85 being the highest r obtained), This is probably due 10 mutual eompen­sation (Yarwood, 1961; Zadoks and Sehein, 1979) of PR components. For each component, except maybe IP, variations among cultivars are gradual. ~everthe­less. practically every pmr of cultivars has al Ieast one component wüh a significant difference, the two most resistant cultivars (Exrico 23 afid A 176) excepted, Determination of PR is laborious and also sensitive to environmentaJ conditions, The: expression of par­tia! resistance is complex and so is its measurement (Zadoks, 1972; Roumen, 1993), depending on envi­ron mental factors (Imhoff et al., 1982), The differ­ences between cultivars for the variúus components may point to a race-non-specific type of resistance (Shaik, 1985), which is oflen beJieved 10 be durable (Parlevliet and Zadoks, 1977; Parlevliet, 1993),

\Vithout genetic ana~ysis oí" the varieties, exposing them lo mao)' phenotypically different rust isolates, nOlhing definit. cán be ,aid about the genetic basis 01' PR and lts durability, The significant correlatíons between various components. of PR could even point lO oligogeníc PR If so, íts durabílity becomos ques­lionable,

Relotive importance oI components

Aoy ooe párameter may not suffíce to explain the PR polential af a particular cultivar, Ourresul! suggest' the indus;on af latent period, ¡nfeclíon efficíency and pus­tule size in the seleclion for partíal resistance, Deter­mination 01' latent period ís time-consuming. Por the evaluation of large numbers of bean cultivars in the greenhouse. infection efficiency and puswle size are preferable tú mínimize labnur. As pustule size and sporulation capacity are strongJy correlated there is no need to ¡nelude the latter for screeníng purposes. Infec~ tíous períod showed po", correlation with other com­ponen!s and should thus be handled with care, Severely ¡nfccted leaves dropped early, befor. spore production came to en end, Smal! pustules can continue 10 Pf<)­

duce spores for a long period and n"netheless have low sporulation, These results underline the importanee of testing for PR components at low infection density for a better expression of PR, as suggested earlier (Par­levliet. 1976),

Research implications

Because of the differen! responses of cultivars for the ditferent parameters ít is unlikely to find one measure representative for all components, The result suggest differences, however smal!, in all the camponents stud­ied, For polycyclíc diseases such as rust (Parlevliet, 1975: Zadoks and Seheio, 1979), even small differ­ences as found here may benefit integrated bean ruS[ management The existence of such differences in aH parameters provides possibilities lo identífy PR eul­tivars al nn early stage in the Ethiopian national bean breeding scheme, Before drawíng far-reachíng conclu­sions, slUdies need to be made (i) on the relationship between component response in a rnonocycJic study on seedling leaves and polyeyclíe disease progress in the field on ad"lt plants, (ii) correlation between com­ponent response at seedlíng and arlult plum slages, (jii) {:orrelation between component response and disease progress in the fieid, and (iv) testing a range of PR cul­tivars with various rusl genotypes (Habtu and Girma,

101

unpublished¡ prevalent in Ethiopia and, eventually, in East Afríea,

Acknowledgements

We are very grateful to David AUen and Theo Jacobs for eritieally readíng lhe draft manuscript, and 10 the plant pathology seetion statT of Nazareth Research Centre for theír help in seed muItiplication, trial m.n­agement and data collection, We thank the Institute of Agricultural Research, Ethiopia, and the Wageningen Agricultural university, Tho Nelherlands, for funding the researeh,

References

Ahn. S.W & S H Ou, 198:: EpidemlOlogical lmphcahons of ¡he spectrum ofre"¡stanceto rice blast. Phytopatholog:yn: 282-2&4.

Ausl. H.J .• A$ Filho & lO.M. Menten, 1984. Resistance ofthree bea.n cullivars 10 Ummycex 1~¡U1SCftU expres¡;ed lhrough sporula­tioll of ¡he fungus. PhYlopath Z 110: 30-·36.

BaUentyne. BL 197&. The genetic bases of resistance tú ruStéáu~d by Ummyces appendlculmux Ín beans (PhtumluJ v,dgam L.). Ph.D. thesis. Universlty of Sydney, Australia. 262 p.

Beehe. S.E. & M PaslOf Corrales, 199 J. Breeding for disease resis­lance. In: A. \3n Schoonhoven and O. Voysest (Edi>.). Cúmmoli Beans: Rescareh forCrop lmprovcmcnt.pp. 561 ~617. CAB Inter­nalional, UK

Chri"c BJ. & J \- Grolh. 19-5::!. Inheritance of resistance in {hree cultivar" of beans [O rhe bean rust pUlhogen and the interactton of virulence and re.ü~tance genes. Phytopathology 12: 771-773.

Coyne, D.P. & "'1 L Schusten. 1975 Gefletic~ and breeding strntcgy for rCSlStance 10 ruS! {Uromyces pha.w;('h! in beans (Piwst!rJ/u.f mlJ.idrtS}. Euphyoc.114: 795-803.

Fromme. ED. & S.A. Wmgarn. 1921. Varietal susc:ep¡ibility ofbt:a.ns io rust. J. Agr Re);, 21.385-404.

Grafton, K.E, G e Weisen. LJ. Liulefield 6.: J.R Stavely. 1985. lnheritance of reSl1;tance io two races of bean rus! In dry edihle beans. Crop SCL 25; 537-539.

Groth,J.V. & NYRK Urs, 1982. DifIerences amongbean cultivars in receptivlty 10 Urmnyce.r Jintu€ojj Vllr. typlW. Phytopathology 72:374-37&

Habtu A. & J.e Zadoks. 1995. Disease progre);s, crop growth and yield studies u; a Pha.'i.eolus ~n rus! puthosystem of Ethiopla. 1. Phylopathol.

Jacobs. Th & l.E Parleviiet(eds.), 1992. DurabiHty ofDiseáse Resif;­t:'.mee. Kluwer , .... cJdemic Publishcn;, Dordrecht, The Nc!herlands, 375 p,

lrnhoff. M.W.. KJ. Leonurd & C.E. Maio, 1982. Pattems ofbean rus! lesíon slze ¡ncrease • .md sporc production. Phytopathology 72: 441-446

Lamberti, P .• Lh.L Waller & N.A~ Van der Graatf (eds.), 1983. Durable Resiswnce in Crop5t. Plenum Press. New York. 454 p_

MehU!., Y.R. & J.c. Zadoks. 1970. Vredosporeproductionand sporu­lation period oí Pucdnia recondila {SI'. tmieion -primary le¡)ve..~ of wheat. Neth J. Plant Pathol. 76: 267-276.

I

102

Seervoort, W.J. & JE ParlcvHet, 1978. Pllrtial resistance oi bnrley lO ¡eaf rust, Puccinia Iwrdet. V. Anaiysis oC the colllpónents of partlall'csíslOl1ce in cight burle)' cultivars. Buphytica 27: 33-39.

Ohm. H.W. & G.E. Shaner. J976. Three components of slow leaf­ru~ting at different gróWlh stages in whem. Phytopotho!ogy 66: 1356-1360.

Pruicvhet. JE. 197$. POJ1inl reslstance ofbarley to leaf rust. Pue­cima ilOrdei. l. Effect of cultivars and developmental sroges 00

iatcnt periodo Euphytlco 24: 21-27. Parlevlíet. J.K. 1976. Eva!u;;¡tion of the concept of horizontal resis­

!Unce in the barley-Puccinia I¡(Jrtlei host-parasite relationship. Phytoputhology 66: 494-497.

ParJevllet, l.E., 1931. Race non-specific disease resistance. In: l.E Jenkyn & R,T, Pl\lmb (eds,). Strategies for the Control of Cereal OiSCDSC, pp. 47-54. Blackwell Scienuñc Publication, Oxford,

Parlevliet. J.E .• 1993. What)$ durableresistance. n general outiine. lo: Th, Jacobs & J.E. P;;¡rlev¡ict (Eds.), Dur.ability of Discase Resl$tance. pp. 23-39. KJuwer Academ.ic Publishers. Dordre<:ht The NetherlMdi>.

P;;¡rlev¡¡et. lE. & H.J. KUlper, ! 977. PArtíal resistance of bn.rley 10

leaf rust, Puc.:cmill/wrdcl. IV. Effect of cuhivar and development $tage Oil infection frequcncy. Euphytica 26: 249-255.

Parlcvliet. l.E. & A. van Ommeren, 1975. Partlm resistance ofbarley to leaf rust, PUCCffllttlwrdel. II. Relationshipsbetween tield tnúls. mlcroplot tests and laten! penocL Euphytica 24: 193-303.

Roumcn, Re, 1993. Panial re",i5fance in rice lo blast and how lO sdecI for it Ph.D, The;.ís. Wageoulgen Agricultural Un\versity, Wageningen, 108 p.

Savary, 5 .• J.P. Bose. ;'vt Noirot & J.c. Zadoks, 1988, PeMUl ru!.! in \Vest Afrka; A new componenl in a multiple pathos}'stcm. Plan! DI~ease 72: [001-1009

Shaik. M" 19&5. Race non~specific resismnce in bean cultivar:; m mees of Umm)'ces appendicultJ1US and íl$ correlation witb lenJ epiderml1i chruacteris!ics. Phytopnthology 75: 478-481

Shaner, G. & F.O. Hess, 1978, Equations foc integraung cúmpo­nents of slow leaf rusting res:istance in wheat. Phytop3thology 68: 1464-1469.

Statler. 0.0. & M.A. MeVey, 19&7. Panial resistance to llromYÓw'es appendiculatus in dry cdibJe beans. PhyíopatboJogy 77; 1101-1103.

Statler. O,D" & J.E. ParlevHet, 1987. factors related lO partiai resjs­tanee ofbafley to Icaí ruS(, PhytOpllthology 77: 549-551.

St:1vcly, J.R" 1984. Genetics of resistunce ro Urom)r:es plwseo/i in á Phaseo[us vulgarH Une reslstant 10 most taces oflOO pathogen. Phympathology 74: 339-344.

SlU\'cly, J.R., G.F Freytag, J.R. Steadman. & H.f. Schwn.rrz, 1983. The 1983 bean ruSf worksnop. Anoual Rcport of Cornmon Beuo Improvemem Coopcrative 26: 4-6.

Turke:osteeo, LJ., 1973. Partíal resistance of tomatoes againsr Phy­wphfhora mJeswns, (he lute blighr fungus. Agricultura! Research Rcports, Wagemngen. 810: 88 p,

Websfcr, D.M. & P,M. Ainsworth. 1988.lnheritance aodstubility ofa ~mal1 pustule reactlOo ofsnap beanslO Uromycesappendiculalus. 1. Aro, SOCo Hort. Sci. 1 \3: 938-940.

YarwomtCE .. 1961. Uredosporeproductioo by Uromycesphasimli. PhYlOpatbology 5 ¡: 22~2i.

Z::ldoks. J.c'. 1972. :-'1odernconceptsof discasc reSts(ooce tn cereal!>. In: EG.H. LlIptoo. et.1L (Eds.), The Way Ahead in Pítmt Breed· mg. pp. ~9-9B Proc. S¡xlh Eucarpja Congress. Cambridge. 269 p.

Zawoks. J.c. & R,D, $chem, 1979. Epiderniology and P!:,mt Díseasc \1anagemenc Oxford Universiry Press. NéW York, 472 p.

burncyer, WJ. & LL. Harter, 1941. Inheritancc uf resistance tú six phYSIOlogicál race$ oi beun rusto J. Agr. Res. 63: 599-622

PI."t Pathology (1995)44, 503-509

Focus expansion of bean rust in cultivar mixtures

HABTU ASSEFA', F. VAN DEr> BOSCH+ and J. C. ZADOKS Deparlment of Phytopathology, Wageningen Agricultural University, P.O. Box 8025. 6700 EE Wageningen, The Neiherland" and + Depanment ol Mathematics, J<Vageningen Agricultural University, Drei}enJaan 4,6703 HA Wageningen, The Netlu:rlands

Radial expanslon of foei in mixtures of susceptible and resistant bean cultivars was studied at two shes in Ethiopia. Tbe roci expanded in a wave-Iike fashion. Al Ambo (1990), radial expansion velocity ranged frorn 6cm per day in mixtures wilh 20% susceptible plams lo 15cm per day in pl0lS with lhe susceptible plants only. At Debre Zeit, tbe velocity ranged from 3 cm per day in a mixture with 20% susceptible plants to 16c1!l per <!ay in plols wíth 100% susceptible plants, At both sites the radial expansion velocity of focí correlated lioearly with tbe logarithm of the fraetion of susceptible plants in the mixture, Velocities of focus expansion at Ambo and Debre Zelt were approximately equa! in plots consistingof susceptible plants onl)', At lower proportions of susceptible plants the velocities at Debre Zeit were lower than at Ambo. Indicauons were given as to the environmentaJ factors responsible for tbe observed dífference between sites. At each site, the variatjon between plots showed a clear spatial pattern~ probably due fo environmental factots.

INTRODUCTlON

Modernization of agricultural practice has resulted in a drastic decline in ínter~ and ¡ntra­specific crop díversity. The widespread use of single resistance genes over large areas led to no inerease in the frequency and intensity of epidemics (Zadoks & Sehón, 1979; Mundt, 1989), Alternative approaches for the rnanage­roent of djseases and disease resistance genes. such a. mixed popul.tion. (Borlaug, 1958), intercropping (Van Rheenen el al., 1981) and inter- and intra-specific diversity (Jensen, 1952; Zadoks, 1958, 1959; Groenewegen & Zadoks, 1979; Wolfe, 1985), were suggested,

The use of varietal mixtures and their potential to control diseases and stabllize yield have becn extensively studied, The effecuvencss of varietal mixtures in redudng the rate of disease progress was established both experimentalIy (Zadoks. 1958; Barrett, 1978; Jeger el al., 1983; Pan", et al., 1989; Pyndji & Trutmann, 1992) and by computer símulation (Kampmeijer & Zadoks, 1977; Mundt & Leonard, 1986; Mundt et al" 1986). The rate of disease progress can be measured by the velocity of focus expansion

·Permanent address: Institute of Agricultural Reseatéh, Nazareth Resear.:h Centre. p.o. Box 436. Nazareth, Ethiopia,

(Minogue & Fry, 1983a,1983b; Van den B_het a/', 1988., 1988b, 1988c), Focal expansion reaches a constant velocity. after an ¡nitial phase of focus build-up (Kampmeijer & Zadoks, 1977). Faclors such as level of resist~ ance, genetic heterogeoeity, plant density. tern~ perature, wind and stochasticity of spore díspersaJ can inftuence the velocity of focus expansion. as was illustrated experimentally (Buiel el al" 1989), analytically (Minogue & Fry, 1983a, 1983b; Van den Bosch el al" 1990; Van den Bosch, 1993) and by computer simula­tion (Zadoks & Kampmeijer, 1977; Zawolek, 1989; Zawolek & Zadoks, 1992),

Van den Bosch el al, (1988c) developed a model w describe the relationship between the veJocity of focus expansion, e, and the propor· tion of susceptíble plants in a mixture, ¡, They showed that

c= A +Bln(J) (1)

The velocity of focus expansion, c, increases linearly with the logarithm of the proportion of susceptible plants in a mixture,f. The purpose of the present study is lo examine this relatinnship for bean rust (Uromycf'S appendiculatus). in mixtures of resistant and susceptible enrnmon bean (Phaseolus i'ulgaris) cultivars, in two different environments"

504 Habtu AsseJa el al.

MA TERIALS AND METHODS 4,------------,

The experiment was conducted during the maio crop growing seasons (June to October) in the research statíons of the PhytopathologicaJ Laboratory at Ambo (1990) and the Institute of Agricultural Research at Debre Zeit (1991). Ethiopia. The two locations represent two different environments. Ambo (2150 metres aboye sea~level), representing the hígber alti­tudes, has more rainy days, more doud cover. less radiation, cooler nights and higher rust pressure than Debre 7",il (1850 metr.s above sea~level). which represents the intennedjate altitudes.

Experimental design

The experirnent was carried out in a 5 x 5 latin square design. The plot ,ize was 4 m x 4 m. Eaeh plot was surrounded by a strip 2'4m \lide planted with wheat. There were five treatments with the mixíng proportions of 1:0 (twice. one treatment as a control without a focus and the otoer one with focus), 1: 1, 1: 2 and 1: 4 susceptible (Mexican 142) lo ;esistant (Negro Mecentral) plants. Seeds of !he susceptible .nd resistant cultivars were mixed manuaIly. From thjs mixture one seed at a time was drawn randomIy and placed along the row at a distaoce of 10 cm between seeds. Eaeh plot con,isted of 10 rOWs of bean plants, planted with a distance of 40cm between rows. One row of resistaot heaos was planled around each plot to reduce interplot interference.

f:stabHshment of mrected plants

Four seeds of the susceptible bean cultivar were sown along with the test seeds at the centre of !ach ptoL At about 3 w-:cks after í"owing, in four of the five treatments, two of the f( ur plants were removed and the remaining planu were inocu­latOO wÍth rust suspensions Lo establish tht foci. Inoculated plants were covered with plastlc bags for 2411 to ensure conditions of high humidhy fOI ¡nfection. A plot planted with only the su,:;ccp­tibIe cultivar was left uninoculattd to serve as a control

Observadons

Observation grids (made of plastic striLg) wilil grid cells of040 m x 0·40 m were placed over lhe plots, with rhe inoculated plants in tht cenu ... :

o

-4' "'0---50 100 150 200

Distance Irom focal ""nlre (cm)

Fig. 1. Focu~ development of bean rust in cultivar mixtures, The natural logaritbm of tbe number of pustules js plotted against distance from the focal centre in cm. Parallellines are fitted 3t fom successive dates: C,.'), 10 days after inoculation (DAI), duy O; ('V), 11 DAI. day 7: (e),;o4 DAl, day 14: (O), 31 DAI, day 21.

cell. Thus eaeh pl"l was divided ¡nlo 100 eells. The development 01' the foei was monitored weekly by cOillltÍng the number of open pustules per grid cell, The numbers of pustules were counted on three trifolíolate ¡eaves at ¡he third, fifth and ninlh lear positions (fmm Ihe top). representing the top, middle and bottom canopy layer.;, re~pectively. When the number nf pus~ tules per leaf exceeded 50. the numbers were estimated in intervals of ten. Tú prevent cross­infection between plots during observation, the boots a:ld h~ .1ds of observers were deaned before enterin ~ the next experimental pIcL The observatiúns I,':ontinued untiJ the bean plants re~ched fuU maturity, although the leaves were BtiU grecn, Data were expre::.sed as the mean number of "Justules per leaf í:!l1d per grid ceH for cae:l pIol, ;: f'ter averaging over the three canopy layer •.

V"II)city of focus expansion

The rate (Jf ;ocus expansion was large compare!! lo the plot size use<!. This implies 'hat the area within which disease severit¡ exceeded a chosf!n va.'le increasea [rom zero to more than the pIot area wlthL1 1 to i' 5 weeks lc such situations the area met:..:; 't of Van den Eo,'¡ '1 et al. (J990) can'10t b~ used, V-le therefl .: appljed the gra.dier,,, method described by Buiel et al. {198~1. Using the observaticll grid, the average n'-,:nt:~~ of pustules was ca1cumted at distances of 20, 6U. ,00, 140and 180cm ."'cm the focal centre.

Focus expansion 01 beall rust in cultivar mixtures 505

~200

f O> • E HlO

~

I • o 10 20

Time (doys)

Fig. 2. Focus developmcnt of bean rust in cultivar mixtures. The distanre in cm of a disease gradient in Fig. J from the first disease gradient is plotted agamst time in days. The radial velocity of focus expansion per pIot was calculated from tne straight ¡¡ne, Dots represent suecessive observatiQn1L

These averages were base<! on a variable number of gnd <:elis. Theoretícally, Ihe taíl of the dlScase profile ís exponentiaL For eaeh plol Ihe loga­rithm of the number of pustules was plotted as a function of the distance from the focal centre (Fig. 1). Parallel straight hnes were fitled using the program STATGRAPHJCS (Statistica) Graphics Corpuration, 1986). Frmn Ihese Iines the horizontal distance lravel1ed. by the disease profile was measured relative to the first observation date, Plotting these disthllces as a function of time (Fig. 2' gave a straight Hne from

1 (a)

20

S

11

u .: 15 .~

t lOr j 15 , ~ 5e

~ ,

0·33 0·2 0,5 1·0

which the velocity of focus. expunslon was c3lculated.

RESULTS

Seans at Debre Zeit grew more vigorously and malured earHer than those at Ambo. The bean ruSl epidernics oríginatíng [rom the point sources, established by inoculation, continued to intensify and expand throughout the growing sea son at both locations. Disease intensity at and near the focal centres was higher at Ambo than at Deore Zeit At Debre Zeit. due ro walerloggíng ofsome plots in one ofthe replications, only four replic-alions were used in the ana~ysjs, The rust iufection in the control plots was negligible, and therefore we did not adjust the data for interference by inoculum from outside sources.

Velocity of focus expansion was plotted as a functlon of the natural logaríthm of the frd,ction of susceptible plant, (Fig. 3). The velodty of focus expansion at Ambo ranged from 6 cm to 15 cm/day, and for Debre Zeít from 3 cm to 16cm/day. The velocity of focus expansion, e, showed variation between plots (wide scattering of dOls) and wíthin plOIS (high standard devia­lions). The fitted tine for Debre Zeit was steeper than tha! for Arr,bo. The calculatcd probabilny that the two lines had the same slope was P 0,08. In plots with susceptible plams only (f = 1), the vel0ctHes, e, did not differ between locations. When .. he fraction of susceptible plants

r (b) J :. , , ,

(-n I !

11

¡ 0·33

Proportion susceptible pla.nts (f) 109 scaJe

Fig. 3. TIte ve1oci!~' "tfocl.'.s expansion, e, as a rl nction ofthc proyDrt;on of susceptible plants.f, In the experimental plots. Dot$ reprf'"5ent obs.:rved e values (mea s per plot), vertical l::lf';: reprcsent their standard dcviations. Data pointsal'" scattered ;:.Iightl;t in thf' horizontal di :~.:ti<1á to 3H,id obscurio.g data points: in similar positions. Thedrawn fine is fitted accordirw '} Equation L (a) Am"!:l., (b) Debr~ ;xit.

506 Habtu Assefa et al.

Ambo,l990 Debre Zel!. 1991 N

• , i 0\ G 0 El ,--

El :-:-1/0 l':J 1+' I -

• ~ ... I~/ • [J • 0 ~ O l..---., O \G 1, .. I

.~

" • ......... _-- ...... • • O L:J 0\ 1.""""' [±Ji O D ~

• .' • _ ... -......... -.....

O D 0 • EJ D [J O D Di , .' ~ "

EJ/ ,

'Ol EJ /a . . L-, • '.

Hg. 4. PosÜions ofbean plots. The signs at each plot indi<:ate wbether the numerical values of the observed veloclty of focus expansion, e, are Larger (+) or smaller (-) than the values calculated by Equation L (O) =: non~in(X':ulated control,

was low (f = 0·2), ¡he velocity, e, at Debre Zeit was smaller Iban that at Ambo. The agreement between lhe vn,:-erved daw u.lld the model was reasouabJe fJr both locat! )ns

Th(! spatial arrangernent of the plots is shown in Fig. 4, The sigas indicate wrl ther the observed velocity is larger (+) or smaller (-) ¡han Ibe velocity calculated from the fitted tines. The c1ustering of positive and negative signs in the field is noticeable. At Ambo (1990), mos! of the neg'dtive signs are clustered in the west of the Heló as indicated by the broken curve. At Debre Zeit (1991), mos! of ¡he negativo sígnsare located in the south~eastern section of tbe fletd.

DISCUSSION

In this paper we showed the velocity of focus expansion, e, to be proportional to the iogarithm of the fraction of susceptible planrs in the mixture, f, as predicte<! by !he model of Van den Bosch el al. (1 988c). There are, however, clear variatiúns between and wlthin experiments. In the foHowing discussion we suggest possible explanations fo! these variations.

There were within-plot variations. The sequen­tia! observations as plotted in Fig. 2 show variation around the regression tine which can he expressed in terms of a standard deviation. Figure 3 shows that these withín-ptot standard deviations are relativeJy high, suggesting high iariability of e in time. In ca1culating the focus

expansion ve)ocity. c. two methods, the arca method (Van den Bosch el al., 1990) and the gradíent method (Buíel el al., 1989), can be used. Studies made on cereal rusts indjcated that standard deviations in the gradient method. which was rather sensiüve to the presence of daughter fOO and background nolse. were much larger than those in the area method. The arca method ís general1y recommended for calculating t, but for relatively small pIot sizes. as in this study. it was not applicable.

VariabUity betweel1 plots ~f similar experimems was evident, suggesting systematic differences between plots. Differences between plots can be caused by several factors, induding wind speed and direction, experimental position relative to ditches, waterlogging, the prcsence or absence oi' trces tn the surrounding areas, etc. Wind influences the speed and shape of epidernics. (Gregory, 1973; Okubo, 1980, Zawolek, 1993). During the crop~growing season (June to October) the prevailing wind direction was south-west. Figure 4 shO\vs no obvious relation­ship bctween tbe wind direclÍon and the "l"' or -signs. The differences in vefocity of focus expansion between plots within locations did nOl depend on \v.ind direction. The experiment ar Ambo was surrounded by tan trees on the west side and up-hills on the south, and the experiment at Debre Zelt was in an open fieJd We \Vere unable to expJain the spatiaJ variation observed at the tWD Iccauolls in terms of field

Focus expansion 01 bean rust in cultivar mixtures 507

environment. Both fields had a light slope and the spatial distríbution of the sígns rather corresponded with the dírection of Ihe slope of the fields.

Ihe mostlíkely explanation of lhe sigo c1usters was a gradient in the experimental fleld created e¡lher by waterlogg;ng (Debro laIl) or by erosion (Ambo) due 10 water. Both could result in low availabilíty of nutrients, mainly N, 10 the plant, in Debre Zeit at the lower end of the field, and in Ambo al lbe upper eud. Several sludíes suggesl nn increase in rust and mildew diseases is associated with increasing application of nitro­gen fertilizers (Nazim el al .• 1982; Jenkyn el al., 1983; Leich el al., 1987). Al low N concentra­tions, biotrophic- fungi such as rust develop poorly (Zadoks & Séhein. 1979). which would resuh in lower values of t. Systematic differences between plots resulting in vRriation in e have a150 been observed in olher studies (Van den Bosch el al., 1990).

The difference i~ slope between the~,regression lines nf Fig. 3 ma)' be explained by variation in environmental conditions. Differences in velocity between locations cou1d arise fram variations in crop growlh, wind ,peed. turbulenec. periods of leaf welness. ele. Atlow f lhe velocity e is higher at Ambo ¡han al Debre lail, bUI al high f lhe velocilY ís abollt equa!.

Van den Bosch el al. (1988c) showed lhal lhe velocity of focus expansion IS proportional to the logarithrn uf the fraction of susceptible plants. The formula does not give insight into the dependence of the velocity on parameters other than the fraction of susceptible plallts in the mixture. The difference between the two experi~ ments, in the slope of the regression Hnes relating focus expansion veIocity to the logarithm of the fractjon of susceptible plants, can 001)' be attributed to the effect of other pararneters. Ihus. the formula 01' Van deo Bosch e/ al. (1988<:) mus! be extended.

Consider a Hne source paraHel lo the front of the focus. The number of pustules produced by this lme so urce at a distance x from this source is

N(x)=,Sof",~exp -.¡2~lx: I I [ I 1 v2 (! O'

where cr ís me standard deviation of the distance of daughter lesions fmm the Hne SOUTCC,! is the proportion of susceptible plants in (he mixture> and ,So is the net reproouctive number oí the disease (Van den Bosch el al.. 1990). This nel reproductive number ¡s the total number of

daughter lesions produced by one mother lesion during the whole course of its Jife jr jt is continuousJy sUITounded only by susceptible plants. Define the effective distance. X4f' as the distance beyond which N(x) decreases below a certain number, K. Then

X,r ~In [::~l (3)

The effective distance is a measure of the distante travelled by the focal front in one generation, Therefore the velúcity of fúcus expansion is proportíonal lo the effective distance

X'ff c=-T

(4)

where l' j5 the generation time. Rearrangement of Equation 3 lead, lo

where

I (T

A=~""·······-. T.j2·

B = iA In ( __ 1 "') ~v2

(5)

(6)

( ])

and e tS the veloc1ty of focus expansion. Since both the generation time, T, and the parameter "­are undetennincd, then A and B can be treated as arbitrary parameters.

For plots consistíng of susceptible planb only. f = 1. Ihi, implíes

e B+ Auln('SO) \ a

(8;

Usíng these formulae we can ñnd an expJanation fOf the observed differences in the slope of the regres5ion lines in Fig. 3. \Veather-conditions are much more favourable for infection and sporu~ lation at Ambo than at Debre Zeit. Favourable temperature and dependable rain resulting in long periods of wetness lead to a hígher nel reproductíon rate, Í'S~h for Ambo than for Deb'" Zejt. Increasing wetness periods may increase thl germinabílily of rusl spores (Imhotf, 1981), Prolonged pcriods of raÍn can also reduce th;~

dispersal of che urediniospores, which is esser ~ tially dependenl on wind (Amorim el al., 1994). The ex.perimental field at Ambo was partly bordered by high earth wal1s and tall trees. whích reduced the effects ofwind and turbulence and thus also reduced (7 in Ambo mOre than in

508 Habtu Assefa et al.

Debre Zeit, Such interacting condjtions could result in almost equal velocities foc f = I at the two locations (Equation 8), yet at the same time result In different slopes of the regression tines in Hg. 3. The standard deviation of the distance travelled by spores at Ambo is smal1er than that at Debre Zeít

(lA < (7Dl1 as argued aboye,

Low (f results in small slopes and high (Y resuJts In large ,lopes (Equation 5). We conelude Ihal the differences in slopes at the two sHes might be expiained by differences in environmental factoes.

The potential of cultivar mixtures foc reducing foliar fuogal disease has been extensively studied in cereals (Jeger el al., 1983; Mundt & Leonard, 1986a; Buiel el al.. 1989; Van den Bosch el al., 1990) and in beans (Mundt & Leonard, 1986b; Panse el al., 1989; Pyndíi & Trutmann, 1992). On the basis of the results obtained from repHcated focal epidemics in two locations, we condude that cultivar míxtures have potential for reducing foliar fungal diseases in beaos as. well. Farmers grow cultivar mixtures for different purposes (Ctawson, 1985). The disease supprcssive poten~ tiaI may b<!-'''ne' reason why farmers in Ethíopía used cu!th ar mi"tures (Westphal, 1974; Institute of Agricultúral Research, 1991 j. Thus, as pan of integrated crop and disease managernent, tradj· tional Ethiopian farmers can benefit more by supp1ernenting rust resistance culüvar:; in their cultivar mixture stratt!gy. \Ve al50 conc1ude that both al Ambo and at Debre Zeit radial expanslon of bean rust epidemics Ín bean cultivar mixtures orjginating from a point source was proportional to the logarithm of the proportion of suscerLíb1e plant:; in the mixture, as de>eribed by Van den Bosch er al. (l988c). We belie\.", ~hat more can be gainea b,l incorporating other parameters SU¡;h as wind, canopy (LAI or LAD), leaf wetness duration or a measure of partial resistance into the ruode!.

ACKI'iOWLED<lEME!'lTS

We than\ the H0¡etta Agricultura] Research Centre and the Plant Protection Research Centre at Amoo lOI p 'oviding field facilities. We are very gra"ful to Aby,e Tilahun, Yílma Abebe and Tesfaye Beshir for theír assistanct whh data coHection, and \Vondimagege for hi:... management oí 'he tria1 at Debre Zeit. We thank Gernt Gort for prOV¡dlllg statisttcal assistan.:e. rinancial sli.Jport was provided by VlageningcT'I Ae;ricultoral University, The

Netherlands, Institute of Agricultural Research. Ethiopia, and CIAT Eastem Africa Regional Office.

REFERE':-¡CES

Amorim L, Berger RD, Bergamin Filho A. Hau B, Mendes BMJ, Bacchi LMA, Vale FXR, Silva MB, 1994. A simulation model to describe epidemics 01' rust of PhuseoJus beans. 11. Validation. Phywpath­%!:y 84.

Barrett lA, 1978. A modei of epidemic deveiopment :n variety mixtures. In; Sean PR, Bainbridge A, eds. Plam Disease Epitkmiology. Oxford: Blackwell Scientific Publications, 129·-37.

Bor1aug ND, 1958, Tbe use of multiline and oomposite varieties tu c,outro! air-borne epidemíc d¡seascs of seJf·poUinated erop plants. In: FirSf lmerfUltional Wheal Genetü.'$ /:')mpQsium Proceedings. Winnipeg: University 01' Manitoba, 12-29.

Buiel AA W, Verhaar MA, van den Bosch F, Hoogkamer W. Zadoks le, 1989. Effect (lf cultivar mixtures on the wave velocity úf expanding yellow stripe rust too in winte-r wheat. Nerherlands J(Jumal (JI Agricultural Scier¡ce 37~ '75·· 8.

CJawson DL, 1985. Harvest security and intraspecific diversity in traditional tropical agriculture. Eco­nornic BOlany 39,56'-67,

Gregory PH, 1973. The Mtcrobiology of ¡fu> Almo­sphere. 2nd edition. Aylesbury: Leonard Hill, 377.

Groenewegen LJ~f, Zadoks JC 1979. Exploiring within·t1eld diversity as a defence against cereal distases: a plea for 'poly-g~notype' vaneties. India" JOllrnaJ ofGern:tkSlJrld Planl Breeding 39. 8J~94.

Imhoff MW, Maln CE, Leonard KJ. 19tH. Effect of temperature, dew period, and age 01' leavC5-, spores, and source pustules on gennination of bean rusr urediospores. PhYfopatn%,?}' 71,577--83.

(nstitute of Agrkultural Research (lAR), 1991. Research on Haricof Bean in Ethiopia, Proceedings 01' a National Works:hop, 1 .. 3 October, 1990. Addis Ababa, Ethiopia: lAR. 114.

Jeger MJ, Jones DG, Orimhs E, 1983. Disease spread of non~specialized fungal pathogens from inoculated point sources in intraspecjfic míxed stand:> 01' cereal cultivars. An'UlIs oI Applied Blology 102. 237--44.

Jenkyn JF .. Firmey ME, Uyke GV, 1983. Effects of nitrogen fertilizer and tridemorph 00 mildew, growth and yield of spring bar ley. }owna! o[ Agricultural Science 101, 517-4J).

Jensen NF. 1952. lntra~var¡etal diversification ín oat breeding. Agronomy Jouma/44. 30~4.

Kampmetjer p, Zadoks Je, 1977. EPIMUL, a Simula¡or 01 Foci and Epidemics in Mixtures. \lu/tilines, and Mosaies al Resistan! 4nd Susceprible Pl,mts. Simu!at¡on Monograph, Wllgeningen: PuJoc. 50.

Leich AH. Sampson DR, Shugar L, Srnid A, CUTnoe WT Kennema e, 1987. Yield, quality and disease resp' ose úf soft white winte; wheat cultivars to

Focus e:tpansion ol bean rust in cullirar mixtures 509

nitrogen fertilization in Ontaria. Canada. Cereal Research Communications 15, 265 ·--72.

Marshall DR, Pryor AJ. 1978. Multiline varieties and disease control. 1. The 'dirty erap' approach with each component carrying a unique single resistancc gene. Theoretical and Applied Genetics 51, 177~R4.

Minogue KP, Fry WE, 1983a. Models for the spread of disease: model description. PhylOpatholog}' 73. 1168---13.

Mínogue KP, Fry WE, 1983b. Models fOf the spread of plant disease: sorne experimental results. Phyto­pathology 73, 1173~6.

Mundt ce, 1989. Modelling disease innease in mix.tures. In: Leonard KJ, Fry WM. ros. Plan! Disease Epidemiology: Genetics, Resisrance. and Managemem. ?\I"ew YQrk: McGraw Hill, 150~81.

Mundt ce Leonard KJ. 1986a. Analysis of factors affecting disease ¡ncrease and spread in mixtures of ímmune and susceptible plants in computer símu­lated epidemics. Ph;liIO{!athology 76, 832-40.

Mundt CC. Leonard KJ, J98-6b. Effect of húst genotype unit arca on development of focal epidemics of bean rust and common maize rust in lIlÍx-lUres of resistant and susceptible p!ants. Phyto­patlwlogy 76. 895~900.

Mundt ce, Leonaro K1, ThaJ WM. Fulton JH, 1986. Computerized simulation of crown rust epidemics in mixtures of immune aod susceptible cat plants with djfferent genotype unit areas and spatial distribu­tions oC ínitial disease. Phyropatlwlogy 76.. 590-8,

Nazim M, El-Shanawanl MZ, Attia MF. Saler MA, [982. Etrect of mtrogen fertHization on slow rustÍng resistance in the wheat cultivar Giza J 55 to leaf rusto Mi:nufiya Journal ofAgricullUral Rcscarch 5, 97 --113.

Okubo A. 198-0. Diffu/iion and Ecologiwl Problems' Marhematlcal Models. Berlin: Springer, 254.

Pause A. DavÍs JHC. Fischbeck G, 1989. Compensation­jnduced yield gaíns in mixtures of eommon bean (Phaseolus vulgaris L). Jouma! 01 Agronomy and Crop St.:ieru:c 162. 347-53.

Pyndji MM, Trutmann p, 1992. Managing angular !caf spot on cornrnon bean in Africa by supp1ementing farmer mix.tures V<-lth resistant varieties. Plan! Disease 16, 1l44-1.

Statistlcal Graphic5 Corporation, 1986. ST.1TGRAm¡CS.

Sta¡is¡ica! Grap}¡ics Sysfem" STSC, lile. Van den BosclJ F, 1993. OptimaJ cultivar mixtures in

focal plant diseases. i'Vl!lherlands Journal of Plant Path%gy!19 (Suppl. 3), 41~50.

Van den Bosch F, Verhaar MA, Huid AAM, Hoogkamer W. Zadóks le, 1990. Focus expanston in plant disease, IV, Expansion rates in mixtures of resistant 3nd susceptible hosts.. Phytopatho!úg,v 80, 598·602.

Van den Bosch F. Zadoks Je. MetzJAJ, 1988a" Focus éxpansion in plam disease. L The constant rate of focus expansiono Phy[opatho!ogy 78. 54~g.

Van den Bosch F. Zadoks Je, Metz JAJ. 1988b" Focus expansión in plant disease. !l. Realishc parameter sparse modds. Phytopat)w!ogy 78. 59~64.

Van den Bosch F, Frinking HD, Metz lAJ. Zadoks Je, 1 98Sc. Focus expansjún jn plant disease. lII, Two experimental examples. Phytopathology 78. 9í9~25.

Van Rheenen HA, Hasselbacn OE, Muigai SOS, 1981. The effoc! of grOWtng beans together with malle on the incidence ofbean dlseases 2nd pests" Netht'r/t.mds Journal (jf Plant Pathology 87, 193~9.

Westphal E. 1974. Pulses in Ethiopia. Their Taxanomy and Af{ricultural Sigmjicanu, Wageningen Centre for Agricultural Publishing and Documentation, 263.

Wolfe MS, 1985. The current status and prospects of multiline cultivan~ and varicty mixtures for di5case resistance. Annual Reriew 01 Ph.vtopulhology 23. 251~73.

Zadoks Je, 1958. Het gelc-róés,t onderzoek. Tienjaren­plan Voor Graaf/otukrzoek (Wagenllgt'j') S. l09~ 19.

Zadoks le, 1959. He! gde-roest oml~r¡fj··l:: T:enjaren~ plan voor Graanofidcrzoelt (Wageni~er) 6, 139~5().

Zadoks Je, Kampmeijer P, 1977. The role or crop populations and ¡heir deployment, iIIustrated by means. of a simulator EPIMUL 76. Annals nl the Nel1' York Academy ofScienc:e 287, 164-90.

Zadoks Je. Schein RD, 1979. Epidemiology and Plant Dúease ,"vIanagemcnt. ~ev.. York: Oxforo Vniversity Press.427.

Z3wolek \-fW. 1989. A Ph.vsical Theoty uf Fo,,'us Dt'l'elopment in Pla1ll Disewe. The Netherlamk Wageningen Agricultura] Un' .érsity, Ph.D. Thcsis.

Zawolek MW. 1991. Shapin{ a focus: wind and stochasticity. Netherlands Juurna! of Plan! Pathof~ O);:")" 99 (Suppl. 3), 241·55.

Zawolck MW. Zadoks Je, 1";92. Studies in focus development. An optjrnllrtl theorem fOr the dual dispersa] of plant pa.thogws. Phytopatho/ugy 82, 1288-97.