Agric.Re~,24(1): 1-15.2003

PIGEONPEA HYBRIDS - A REVIEWG.C. Bajpai, Jogendra Singh and S.K. Tewari

Department of Genetics and Plant Breeding, College of AgricultureG.B. Pant University of Agriculture and Technology, Pantnagar - 263 145, India

ABSTRACTThe present review focuses on international and indigenous research efforts in developing pigeonpea

hybrids for harnessing higher productivity per se, strengthening of seed research and seed production.'Hybrid vigour and exploitation of heterosis for earliness, uniformity)11 maturity, better partitioning andyield potential of hybrids has been reviewed critically. Availability of male sterility, genetic as well ascytoplasmic and genetics of male sterility have been evaluated. Development and diversification ofmale sterility system led to release of hybrids viz., ICPHB, PPH4, IPH732 and AKPH 4101 etc. Dueto lack of effective seedling markel'S, hybrids based on GMS have limited scope, however, efforts are On

in stabiliZing cytoplasmic male sterility and its use in development of hybrids with increased yieldpotential in pigeonpea.

Because of vegetarian food habit,pulses are a major source of protein for largesection of Indian population, yet their per capitaavailability has declined from 64.6 g/day in1951-56 to about 43 g/day in 1996-98 asagainst recommended 85 g/day. While areaunder pulses in India since 1970-71 till date,has remained almost constant at 20-24 millionha, though, production and productivity haveshown positive trends. It is estimated that,. tomake pulses available at the recommended levelof 85 g/day, India will require an annual pulseproduction of 31.02 million tonnes for its 1billion population in the year 2001.

The data reveal' that India dominatesthe scene forpigeonpea cultivation.The world~rends largely reflected the situation in India,where, growth rate of area and production,exceeded 2%/year from 1970-90 (Srivastavaeta!., 1998). However, the growth rate of yieldin India were almost stagnant during theaforesaid period. This stagnant growth inpigeonpea productivity may be related to thecrops of relatively low status in the croppingsystem. Even today, pigeonpea like other pulsesalso considered a subsidiary crop. It is oftensown to marginal soil and is usuallyintercropped with crops such as sorghum,pearlmillet and cotton. Pigeonpea as a crop ofsecondary importance in many of these

systems, neither it receives little or nopurchased inputs like fertilizer, herbicide,pesticide etc. nor does it attract much of thecrop management attention. Though, releaseof early, medium and late pigeonpea varieties/hybrids in· recent years showed that theproduction has attained upward growth andalso confirms the impact of new technology.Recent release of pigeonpea hybrids viz., ICPH­8, PPH-4, COH-1 etc. may be more profitablefor farmers and crop may gain a status as acash crops with appropriate transfer oftechnology under lab to land programme.:

Prospects and opportunities of hybrids ,Pigeonpea has shown substantial

amount of nowadditive genetic variance(Sharma et a!., 1973; Reddy et a!., 1981;Saxena eta1., 198Iiand hybrid vigour for yield(Solomon eta!., 1957). The discovery of stablegenetic male sterility (Reddy et a!., 1978)coupled with its outcrossing nature, has openedthe possibility of commercial utilization of theheterosis in pigeonpea.

The genetic male sterility of translucentanthers requires roguing of 50% of the normalfertile plants from the female roWs in hybridseed production blocks at flowering and theidentification and collej:tion of seeds from malesterile plants in the maintenance block. Todate, it has been demonstrated that full seed

2 AGRICULTURAL REVIEWS

set is obtained if one fertile pollinator parent issown after every six male sterile rows (Saxenaet aI., 1986). The available sources of malesterility have been transferred to several geneticbackgrounds in different phenological groupsthat also have resistance to various diseases(Saxena et aI., 1986). Generally successfulhybrids are produced from combinations,where, SeA effects result in conside'rab'leheterosis in the Fl generation. However, to findthese combinations and develop a successfulhybrid programme, it will be necessary to testa large number of hybrids.

The available technology forpigeonpea hybrids production has potential todouble the productivity of pigeonpea. Hybridsrecorded more than 25% increase in grain yieldover improved local varieties underdemonstrations and encouraged farmers togrow hybrids with more confidence. Forforming strategies for sustainable hybridproduction, developmental efforts on hybridsare essential. Focus should be on breedinghybrid varieties resistant to biotic and abioticstresses, stabilizing of yields and enhancingproductivity in pigeonpea.

Genetic male sterilityI. Mechanism

The discovery. of three sources ofgenetic male sterility (Reddy etaI., 1978, Walliset aI., 1981, Dundas et aI., 1982) and theprevalence of sufficient natural outcrossing byseveral insect species (Williams, 1977, Onim,1981) led to the development (Gupta et aI.,1983) of pigeonpea hybrid. The three sourcesof male sterility were found to occur due to thefailure, at different stages, of male meiosis.Reddy et al. (1978) reported that male sterileswere identifiable by non-dehiscent, flat,translucent anthers. This type of male sterilityis designated ms l . Male meiosis proceedednormally in this male sterile line up to theformation of tetrads. then degenerationoccurred because of non~.eparation of tetrads.

The tapetum was found to be intact, whereas,in normal cells it disintegrated as meiosisadvanced. In the male sterile line identified byWallis et al. (1981) which is designated ms

2,

the stamens are brown, shrivelled andarrowhead shaped. Meiotic failure of this sourceof male sterility occurs earlier than it does inm<; I' Pollen mother cells degenerate at thetetrad stage with the rupture of the nuclearmembrane. The anther morphology of the thirdsource of male sterility is similar to that foundby Wallis at al. (1981). MeiullL luilure occurredat the pachytene stage Le. earl1~1 tlk~n the othertwo male sterile types (Dundas et aI., 1982).Krishnamurthy and Gnanam (1987) studiedthat in male sterile translucent (MST) anthers,the tapetum appears abnormal frorn the earlytetrad stage, the enlarging cells encroachinginto anther locule, the microspore tetrad losetheir viability and shape and eventuallydegenerate. Pandey et al. (1996) observedmale sterility associated with obcordate leafshape and had widely opened free and threadlike keel petals of the flowers, which mayencourage cross-pollination.

II. GeneticsSaxena et al. (1981,b) reported that

male sterility was controlled by a single recessivegene. In Cajanus volubilis x Cajanus cajancrosses monogenic recessive behaviour of themale sterility with reduced anther type wasconfirmed (Patel et aI., 1998). Male sterilityshown by translucent anthers is controlled bysingle recessive gene ms

l. Another source

characterized by brown arrow-head shapedanthers is also controlled by a single recessivegene ms2 • Both of these are controlled bydifferent independent genetic systems (Saxenaet aI., 1983).

III. Induction of male sterilityA. Through crosses

In pigeonpea male sterility coupledwith natural outcrossing can be utilized toimprove populations and develop high yielding

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hybrids. The male sterile Prabhat DT line, bredat ICRISAT is most popular and commerciallyused in development of short duration hybrids.Govil et al (1994) developed a short durationms Pusa 33. QMS-1, ms-ICP 3783, HUA-7are some other male sterile lines of longduration group (Rajni Raina et al, 1996).Pandey and Singh (1998) developed ams­DAMS1, which might be a good source forhybrid breeding programme of Northern partof the country. Apart from these PMS-1 andIMS-l are also being used in hybriddevelopment. Patel etal (1998) obtained stablems in crosses from C. vo/ubi/is x C. cajancultivars. The conversion into male sterility isin progress in BON 31, MA 97, ICPL 83024,ICPL 86023, AL 201, AL 230, AL 688, AL83015, Manak, Paras, ICPL 87051, BON 7,HYD 185, ICPL 8863, P 869, P853, AKT6,ICPL 83027, Bahar, NDA 88-2, DA 11, Pusa9, T7, ICP 8860 and PDA 85-1 (Srivastavaet al, 1997).

Variability of four types of male sterilitywas expressed in crosses with C. vo/ubi/is x C.cajan at PKV, Akola ((Srivastava et al, 1997).The cross, (c. vo/ubi/isx ICPL 83024) x AKMS7B, showed small anthers, purplish in colour,irregular in shape and non dehiscent typewithout pollen powder. The cross (c. vo/ubi/isx ICPL 83024) x DA 6B showed normalanthers, blackish white, non- dehiscent andwithout pollen grain. The cross, DA 6A x (c.vo/ubi/isx ICPL 83024rshowed unstable malesterility, pale yellow anthers with normaldehiscence. Another cross, AKMS-7 x (c.vo/ubi/is x ICPL 83024) showed insensitivemale sterility with yellow dehiscent anthers,where pollen powder was sterile in all theseasons.

B. Through chemicalsPandey et al (1996) induced male

sterility in long duration pigeonpea varieties viz.,Bahar, DA11 and Pusa 9 by chemical mutagenusing streptomycin sulfate (SS) and sodium

azide (SA). In other studies, chemical mutagens,viz., Streptomycin and Terramycin byIlPR,Kanpur, Sodium azide, EMS by !ARI, EMS andDES by GAU, S.K. Nagar, Streptomycin,Sulphate and Sodium azide by RAU Dholi havebeen used to transfer male sterility in diversepigeonpea genotypes (Srivastava etal, 1997)'.Complete male sterility to varying degree ofpollen sterility was observed in these cases.'Using GMS, many male sterile lines viz., msPrabhat NOT, ms Prabhat DT, IMS-1, QMS­1, msT 21, ms 288, ms 3783, ms 7035, msCo-5, ms BON-I, ms C11, ms BWR 370,AKMS-2, -5, -6,. -8, -9, -10 etc have beendeveloped in past by various breeders.

C. Through physical mutagenPlants with varying degree of male

sterility/pollen sterility were isolated throughinduced physical mutagen as Gamma ray byscientists at IIPR, Kanpur, IARI, l'Jew Delhi,HAU, Hissar, GAU, SK. Nagar, TNAU,Coimbatore, NDUA&T, Faizabad and BARC,Trombay. Verulkar and Singh (1997) obtainedspontaneously a male sterile UPAS 120 plant,which had white translucent anthers withcomplete pollen sterility. Inheritance studysuggested that the male sterility was geneticand controlled by a recessive gene.

Cytoplasmic genetic male sterilityI. Mechanism

Male sterility, the inability of a bi~xual

flower to produce functional male gamete orviable zygotes result from one or two genecontrol systems and is of nuclear genomicorigin, often designated ms and is cytoplasm­nondepend(mt for its expression and designatedas genic male sterility (g mst-Ariyanayagametal, 1993). The second less prevalent systemresults from the interaction of nuclear and ,cytoplasmic factors. Itis generally accepted thatspecific genes of sterile cytoplasm interact withthe fertility restorer gene (fr.) of the nucleargenome to produce male sterile phenotypes.The inheritance is non-mendelian as

4 AGRI!=ULTURAL REVIEWS

transference of the sterile cytoplasm is throughthe maternal parent. This system is designatedas gene cytoplasmic male sterility (g-c-mst).

II. Genetics of cytoplasmic genetic m~le

sterilityThe genetic factors associated with g­

c-mst are highly variable. More than one controlsystem may exist in the same crop. Single anddouble recessive gene controls have beenreported in a large number of monocots anddicots. Control by three, four, five and manyrecessive genes though less frequent, has alsobeen reported in crops such as sorghum, pearlmillet, sugarbeet, flax, alfalfa. Dominant geneaction has been found in wheatcarrot, potato,red clover whereas, polygene action noted insunflower, flax, alfalfa, peadmillet andinteraction of dominant and recessive genes incarrot and redclover was noted (Kaul, 1988).Different cytoplasm types of are known inonion, rice, petunia, sorghum and wheat. Theexistence of non allelic 'fr' genes and differentcytoplasm types contribute to complex geneticcontrol of g-c-mst (Kaul, 1988). Genic malesterile line QMS-1 when treated with sodiumazide at 0.025% for 48 hours or streptomycinsulfate at 500 mg kg'! for 24 hours appearedto undergo IJ1utational chan.ge from thegametophytictYPe of stE!rility maintenance tosporophytic maintenance. The sterility wasmaternally inherited and resembled to g-c-mst(Ariyanayagam, 1993). The maintainer was aheterozygous sib. Fertility restoration occurredwith many normal genotypes. In another studysterility resulted from interactions of genomicand cytoplasmic genetic factors of cells, thelate appearance of sterility symptoms suggestedthat either the interaction did not begin untilthe pollen grains differentiated or that the timelapse for the interaction to take effect waslong (Ariyanayagam et a/., 1994). In Cajanussericeus x Cajanus cajan hybrids, Wanjariet a/. (19'98) observed monogenic recessivemale sterility in two progenies, whereas,

another three progenies expressed dominantsterility. Thus, male sterility mechanism wasgoverned by. recessive as well as dominantgenes. Pod and seed set was studied in c-mslines by Rao eta/. (1996), he observed that c­ms plants were female fertile and were capableof an acceptable level of pod set under naturalpollination. Thus, these should pose noproblem in developing commercial hybridswhen cms lines are fully developed. Wanjariand Patel (2001) suspected apomixis in secondbackcross progeny on recurrent parent ICPL85030 to develop cytoplasmic male sterility.In BC4 generation, plant to plant backcrossesdeveloped by mechanical pollination with thepollen from same recurrent parent, revealed 5progenies with apomictic seed developmentwithout any sexual reproduction while fourprogenies showed 33.3 to 52.2% sexual seeds.

III. Induction of cytoplasmic genetic malesterility(A) Through crosses

Ariyanayagam eta/. (1993) haveindicated the prevalence of differences amongspecies, and among accessions within speeies,for the occurrence of male sterility as well asthe level of male sterility in successivegenerations, for instance, C sericeus, Cscarabaeoides and C acutilolius as femaleparents in crosses gave a higher frequency ofsterile progeny than C. albicans. Evenaccessions within the three promising speciesresponded differently to selection for the trait.Among the C scarabaeoides accessions, PR4562, was promising and among the C.sericeus accessions, EC 121208 gave goodresponse in triple and backcrosses. However,a combination of triple and backcrosses wasfound to be effective in overcoming theapparent antagonistic effect between thecytoplasm and genome of the parent. Thefemale sterility noticed with direct backcrossingwith pigeonpea parent was less prominentwhen several pigeonpea parents were

Vol. 24, No.1, 2003 5

introduced. This strategy was effective' ininducing genetic-cytoplasmic male sterility inC sericeus x C cajan crosses. .

In a· ;;mother search for sources ofCMS, 5 species -of Atylosia, 5 of RhYQchosiaand 2 of Aemingia were crossed with 9 varietiesof Cajanus cajan (Rajni Raina et al, 1993),however, only one plant' from the cross C cajancv. T.21 x A. mOilis was found male sterile.Analysis of PMC meiosis showed no separationof tetrads, as well a~' pollen grains were alsonot formed. The plant was maintained bybackcrossing with T21.

Hybridization with Cajanus sericeusindicated possibilities of cytoplasmic geneticmale sterility (Wanjari etal, 1998). The hybridsof C sericeusx C cajan showed 44% pollenfertility. Laggards and unequal distribution. ofchromosomes were seen at Anaphase I. Onthe basis of pairing behaviour, sevenchromosome pairs are seen to be common toboth the parents and two pairs had been in thetranslocation in the course of evolution.Rathnaswamy et al (1989) developed a c-g­mst by crossing two wild species, Cajanuscajanilalius and C acutilalius with genic malesterile lines"of C cajan (ms C05). Interspecificcrosses between Cajanus scarabaeaidesandCcajan 'has resulted in isolation of progenies,havi~g 100 per cent pollen sterility. From theresuits' it is evident that a stable CMS systemas a' line (~~8A) and its maintainer B line (288B)is now available (Srivastava etal, 1997). There

. . is a definite interaction of nuclear genomederived from recombination between C.sericeus and C cajan, use of this source inisolation of CMS line is in progress at BARC,Trombay and ICRISAT, patancheru. Ina~ditipn., four types of male sterile plants wereisolated in derivatives of Cajanus valubilis xCajanus cajan. The isolated male steriles alsoshowed heteromorphic variation of filamentlength in relation to length. of style, CMSprogenies identified at GTSs stage in C sericeus

(EC 121208) x ICP 88027 and 90-100%male sterility developed. In seiirch for CMS,various sources of male sterility using aliengermplasm as C cajanilalius, C albicans, Cscarabaeaides, C sericeus, C platycarpus, R.bracteata at IIPR, Kanpur, C valubilis, Cplatycarpus, R. bracteata, C lineatus at IARINew Delhi, C cajanilalius, C lancealat1, Cvalubils, .C. .acutilalius, C. platycarpus,Flemingea similata at PAU, Ludhiana; C.cajanilalius,.C valubilis, C sericeus, C lineatus,C lanceolatus, C scarabaepidesat PKV, Akola,S. scarabaeaides, C ,.seric~us, C caja/~ilaliusat GAU, S.K Nagar, C cajanilaliusat TNAU,Coimbatore, C .mallisat'BHU, Varanasi Wereused in crosses with C'cajan (Srivastava et a!.,1997). Variable 'sterility (10% to 99%) tocomplete sterility were noticed in F anddifferent segregating populations. Th~ugh,barrier in crossability was noticed with C.valubilis and C. platycarpus. The work atICRISAT confirmed the stability of male sterilityin GT 288A across the location and environment(Annual Report, I1PR, 2001-2002).

B. Through mutationIn a study at NDUA&T, Faizabad a

cytoplasmic male sterile source was isolated asa spontaneous mutant (ms ICP 6042 and msICP 1024). In ms ICP 6042 (A line) malesterility was maintained by Bahar Le. B lineand sterility was restored byPusa 9 (R line).Similarly other male sterile line ms ICP 1024(A line) was maintained by ICP6622, Bahar,T7 and NDA 88-2. The male sterility of msICP 1024 was restored by NDA~93~1, Pusa9, and ICP 2905, R-line (Srivastava et a/.,1997). Another spontaneous mutant in Bahar(DAMS-I) was found less sensitive to lowtemperature under Dholi condition. The anthercolour of this mutant was white (Srivastavaeta!.,1997). .

In hybrid of C cajan x A. platicarpusapplication of gibberellic acid, NAA and kinetinprevented early embryo abortion, later embryos

6 AGRICULTURAL REVIEWS

were cultured and hybrid pollen showed 41.5(X)sterility. In a another study Dundas et a/. (1987)studied hybridization between pigeonpea andtwo native Australian species, Aty/osia acutifo/iaand Aty/osia p/urinora. The hybrids showedhigh level of sterility, thus have potential foruse in pigeonpea hybrid improvement.

Role of wide hybridization,Jaswinder et a/. (1993) studied wide

crosses of C cajan with the wild relatives Cp/atycarpus, C cajanifo/ius and Rhynchosiaaurea. They observed that application of thegrowth regulators ~iz., gibberellic acid andkinetin helped to maintain developing hybridpods upto 19 days after pollination, whereas,untreated controls survived for only 5 days.Embryo age was found. critical for plantregeneration, with embryos less than 11 daysold fail to develop. In a search for CMS, oneplant from the cross, C cajan cv. T-21 x A.mol/is was found male sterile. The analysis ofPMC meiosis showed no separation of tetradsand no pollen grains were formed. The plantwas maintained by backcrossing with T-21(Rajni-Raina et al, 1993).

Dodia etal (1996) studied growth anddevelopment of pod borer, He/icoverpaarmigera en pigeonpea varieties T151 and thewild relatives viz., C scarabaeoides. Ccajanifo/ius, C reticu/atu!>" C sericeus and F

1generation of the cross C scarabaeoides' Ccajan.Larval and pupal mass, developmentalperiod and pupal length were alliowerfor larvaefed on wild flowers as compared to cultivatedpigeonpea. Growth and development of Harmigera was adversely affected on flowers ofall wild species and few larvae survived tomaturity.

Hybrids between 13 accessions of Cp/atycarpuswith ICPL 88014 and ICPL 85030as pollen donors failed to give fertile hybrids(Saxena etal., 1996). IPCW 64 and IPCW 70produced hybrid plants with both pigeonpealines but hybrid seeds were undeveloped and

failed to germinate. Reciprocal pollination usingC p/atycarpusas male parent was unsuccessfulin a study done at ICRISAT.

IV. Molecular analysisSeveral distinct lines of evidence

suggest that genes which control staminalsterility in maize, sorghum, sugarbeet andwheat are iocated on mitochondrial (mt DNA)and not on chloroplast (ct DNA). Observationson DNA sequencing of unique genes of theplant mitochondrial system provide convincingevidence for alteration of mitochondrialgenome to be the major cause of CMS. PlasmidDNA's are natural components ofmitochondrial genome and they can beactivated for transposition by genomic stress(Srivastava, 1985). CMS is a' maternallyinherited trait with the plant remaining femalefertile, while the pollen formation is abnormal.CMS was manifested as a result of theincompatibility of the nuclear" mitochondrialinteraction and the changes were mainlyencoded in the mitochondrial genome.

The differences in the restrictionfragment patterns 'among the variouspigeonpea cultivars could be the result of interand intra molecular rearrangements within themitochondrial genome, which is a commonphenomenon in higher plant mitochondria.The studies on another morphology also dearlyindicated the differences between cytoplasmicmale sterile lines and the genetic male sterilelines.

RFLP analysis of total genomic DNAfrom three putative CMS progenies derivedfrom crosses between the wild species Csericeus and cultivated pigeonpea was studiedby Sivaramakrishnan etal. (1996). Results alsosuggested that male sterile lines derived fromthese crosses had mitochondria of female wildspecies parent. The results presented bySivaramakrishnan et al. (1996) on the crossesbetween the wild species C sericeus and thecultivated species C cajan produced male sterile

Vol. 24, No. 1. 2003 7

lines having the mitochondria of the later.Souframanien et al (2001) used randomlyamplified polymorphic DNA (RAPD) markersfor the identification of two pigeonpeacytoplasmic genic male sterile lines, 288A and67A derived from crosses between the wildspecies Cajanus scarabaeoidesand C. sericeusand the cultivated species C cajan, respectively.The RAPD analysis of the male sterile line andmaintainer line can be of practical applicationand also in establishing the genomic stabilityof the male sterile lines. The identified putativemale sterile marker OPC 11600 may be usefulin hybrid pogeonpea breeding programme.

Hybrid vigour in pigeonpea and hybridevaluation

Solomon et al. (1957) was the first toreport hybrid vigour in pigepnea. To realize ahigh level of hybrid vigour for yield Shrivastavaetal. (1976), Reddy eta!. (1979) andVenkateswarlu etal. (1981) suggested selectionof parental lines belonging to diverse maturitygroups.

Singh et .al (1983) reported upto22.1% mid parent heterosis in a cross Muktax UPAS-120. Some experimental hybrids outyielded the best control cultivar by over 100oA)(Saxena et al, 1989). Anand Kumar (1990)evaluated ICPH-8 along with ICPH-11 andseven other hybrids and observed yield increaseupto 22% over best control, Pusa 33. Hybridshad more branches and pods as compared tothe controls. In another study, heterosis underirrigated conditions ranged between 171!1.) to67% as compared to 0 to 45% under non­irrigated conditions. Based on it, it appears thathybrids adapted to specific situations may haveto achieve high yield. Jain and Saxena (1990)observed that 11 medium duration hybrids fromcrosses between ms 3783 and advancedbreeding lines had significantly higher yield thancontrol, C11 variety. All hybrids also exhibitedpositive heterosis for plant height, seeds/podsand seed yield. Patel et al. (1993) studied 60

pigeonpea hybrids involving three genetic malesterile lines and respectively, eleven and ninemedium and short duration pollinators, thesehybrids significantly exceeded their parents forharvest index. Identification of stable geneticmale sterility aroused the interest in thedevelopment of F, hybrids in pigeonpea(Sandhu et aI., 1994). In the experimentalhybrids numerical superiority over best check,over the years ranged from 1 to 39%. In theexperimental hybrids yield gain upto 509/0 overbest check have been reported by variousworkers. Shrivastava and Khan (1994) studiedeight hybrids of Cajanus cajan and their pollenparents and seed parent (ms3783) for seedlingmorphology upto 6 days after germination. Ananalysis of variance showed significantdifferences between the hybrids and theirparents for radicle length on the 2nd .day·butnot for root length on days 4 and 6, plumulelength or epicotyllength. Heterotic responsefor root characteristics was highest on the 2nd

day, decreasing gradually on the 4 th and 6th

days. Heterosis for epicotyllength and plumule'length was poor compared to that for radicleand root length based on mid-parental values.A positive heterotic response was noted forradicle, root, plumule and epicotyllength.

Gowda et al (1996) noted significantpositive heterosis for grain yield in hybrids viz.,AKPH 9071 (181.79%), AKPH 4186(151.03%) and KBPH1 (119.46%).Superiority of early pigeonpea hybrids was dueto significant and positive heterosis for numberof pods per plant. So higher yield could beharvested from early pigeonpea hybrids.Twenty four pigeonpea hybrids, derived fromcrosses between 3 genetic male sterile lines(AKMS2, AKMS 11 and AKMS 21) and 8diverse testers (ICP 8863, ICPL 87119, BSMR175, BSMR 736, BWR 171, AKT 9221,C11and BDN2) were studied by Khorgade et al(2000), significant heterosis was observed inall traits studied. Significant heterosis over the

8 AGRICULTURAL REVIEWS

mid-parent and control cultivar was recordedfor seed yield per plant in the hybrids, AKMS11 x AKT 9221, AKMS 11 xC11 and AKMS21 x Cll.

Out of seventy one the highest grainyield of 2314 kg and 3981 kg ha- l wasrecorded in the main crop from the hybrid,NDPH 94-20 and RAUPH 9507, respectively.However, from of ratoon crop, the highestgrain yield ofl4-13 kg and 1300 kg ha- l wasrecorded from the hybrid RAUPH 9001 andRAUPH 9501, respectively while the checkvariety, Bahar'produced 1326 kg and 1285kg ha-1, respectively in main and ratoon harvest.Thus, raising of ratoon crop in long durationpigeonea hybrids in the northern part of Indiamay not be profitable (Pandey, 2000). Pathakand Sidhu (2001) noted as high as 5 t ha-1

yield from some of the hybrids which signify abreak through in yield of the hybrids. Sidhueta!. (2001) observed more than 25% heterosisover the check hybrid PPH-4 with regard tograin yield. An analysis of these topJ9 hybri9sfurther rev~aled that high heterosis' for yieldappeared to be related with high heterosis forsome of the yield components.

Component analysi~ of hybridsComponent analysis of hybrids have

shown high yield in the heterotic crosses to beclosely associated with het€rosis for pods perplant, number of primary branches, plant heightthat all contribute to increased total biomass(Reddy et ai., 1979, Marekar, 1981,Venkateswarlu etai., 1981, Saxena et ai.,1986, Cher(ilu eta!., 1989). Compton (1977)suggested that inbreedin~ depression is betterevidence of dominance than heterosis. Withthe discovery of genetic male sterility inpigeonpea (Reddy eta!., 1978; Saxena eta!.,1983) and the presence of natural outcrossing,it ha~ been possible to breed hybrid pigeonpeavarieties. In order to justify a major thrust in abreeding p~rgramme on F 1 hybriddevelopment, a large dominance variance is

essential. Heterosis, which can result from alltypes of non-additive gene aCtion, such as.additive x additive, need not necessarily indicatea high level of dominar1ce. In pigeonpeainbreeding depression does not seem to besignificant (Nene et a!., 1990). Ther~fore, inall theoretical probabilities, it is possible to selectpure lines equal in performance to F1 hybridLe. may be possible to fix a considerable partof the observed heterosis. .

In a study of about, 60' mediummaturing hybrids,' as a result of high heterosisfor pods, plant height and 'branches, manyhybrids showed significant heterosis for seedyield/plant (Patel et a!., 1991). Heterosis forseed yield over better parent was highest incrosses, MS3A x ICPL 78-1 and MS Prabhatx ICPL 384 (80 and 78%, respectively) whencompared with the standard variety BDN-2.Omanga et a!. (1992) estimated high GCAvariance than SCA for yield, pods, seeds/pod,seed size and days to flowering in hybrids usingMS-3A, MS-4A and MS-Prabhat, male sterilelines. MS-Prabhat appeared to be a goodgeneral combiner for dwarfness, earliness andseeds/pod. Tester, C11 appeared to be the bestgeneral combiner for yield. Patel and Patel(1992) observed high SCA effect for seed yieldin the hybrid MS Prabhat x HY3A. Patel andPatel (1992) noticed predominance of additivegene effects for days to maturity and 100-seedweight and of non-additive effects for yield,branches, pods and seeds per plant in hybridms Prabhat x HY3A. They further revealedmajor role of additive genetic variance for daysto maturity and 1DO-seed weight and that ofnon-additive genetic portion for seed yield perplant, branches, pods and seeds/pod.

Sidhu et ai. (1992) recordedinformation on reciprocal cross effects (RCE).Significant GCA, SCA and RCE differenceswere observed for all characters except seedweight, where, only GCA effects weresignificant. Narladkar and Khapre (1994)

Vol. 24, No.1, 2003 9

accounted significant heterosis in hybrid x AL 259, gave the highest SCA effects forMSHY9 x BON 2 over the better parent, seed yield and out yielded the control hybridstandard hybrid ICPH-8 and standard variety PPH-4 by a margin of 67.9,34.9 and 17.5%,BON 2 for grain yield. Patel eta1 (1993) studied respectively (Sidhu et a!., 1996). Ohedhi et a!.60 pigeonpea hybrids involving three genetic (1997) observed a significant rOle of additivemale sterile lines and revealed importance· of and non-additive gene action in a combiningboth additive and non-additive components of ability study of 50 hybrids based on 5 GMSgenetic variance in the inheritance of harvest lines and 10 short duration lines. In general,index, days to flowering, plant height and hybrids having high heterotic estimates for seedreproductive period. The non-additive portion yield included both or at least one goodwas also pre dominant for all the traits except combiner parent. In a line x tester study, Ajaydays to flower where additive genetic variance Kumar and Srivastava (1998) found 77.91%played a major role. SiJlgh' et al (1995) to 110.07% heterosis over better parent forreveaied that the maximu~ weight sh6'Glcl be , seed yield in hybrids involving three male sterilegiven to pods and primary branches during lines and twelve; male fertile (Pollen parents)selection. In general, cross combinations of long duration. Gene action wasinvolving parents of different growth habit predominating non-additive for the charactersexpressed high heterosis and low inbreeding studied. Iidepression, whilst cross combinations involving Chandirakala and Raveendran (1998)parents of similar growth habit exhibited low observed·significance of both gca and scaheterosis and high inbreeding. depression for variances for yield and yield contributing traits,most of the traits (Gumber et aI, 1996). Two hybrids MS C05 x ICPL 87 and MS COSNarladkar and Khapre (1996) studied that x ICPL 89020 were also identified assuperiorhybrids exhibiting more heterosis for grain yield hybrids. Significant heterosis over better parentwas high in crosses involving male sterile line was observed in all traits except pod/clusterMSHY-9 as the female parent rather than male (Manivel et a/. , 1998). The analysis revealedsterile Prabhat. Manifestation of heterosis for that both additive as well as non-additive genegrain yield was due to days to maturity, lower effects were important for all the traits. Maleheight of first effective fruiting branch and sterile line MS Prabhat NOT was the bestincreased number of primary branches and combiner for yield/plant. Most of the crossespods/plant. exhibiting high sca effects involved one good

A study involving three male sterile and other medium or negative combiners.lines, CMS Prabhat, PMS-l IMS-l and 11 Thus, crosses involving diverse parents anddiverse pollen donor lines of pigeonpea showing high sca effects for yield/plant couldexhibited preponderance of additive genetic be successfully utilized for' exploitation ineffects for plant height, primary branches, pigeonpea improvement. Wanjari eta!. (1998)secondary branches and pods/plant. Non- studied combining ability using 4 male sterilesadditive gene effects were noted for flowering, and 6 diverse pollinators. The cross MSP3 xmaturity, seeds/pod and 100-seed weight, AK22 was highest yielder and involved bothwhile both additive and non-additive gene the parents having high gca effects. It was likelyeffects were present for pod bearing length of to be an additive x additive combination, whilemain stem and seed yield/plant (Sidhu eta!., second hybrid MSP9x AK 31 was produced1996). Three top yielding hybrids, PMS 1 x from the parents each of which had negativeAL688, MSPrabhatxAL 101 and I\1,S Prabhat gca. It had expressed high heterosis (58.82%)

10 AGRICULTURAL REVIEWS

over the better parents. Singh et a/. (1999)studied twelve mal~ sterile hybrids and notedpods/plant as the most important yield

.. contributing trait was number of pods/plant.Studies carried 'over by Hooda eta/. (2000) on

. forty hybrids indicated that heterosis andepistasis were independent of each other.Anyone or both parameters can be exploitedfor the improvement of yiekl and itscomponents in pigeopnea. A study involvingthree genetic male sterile lines and eight testersof pigeonpea indicated the predominant roleof additive gene effects for yield' and yieldattributes except plant height (Khorgade et a/. ,2000). AKMS 21 was best general c;ombinerfor number of clusters per plant, proteincontent, 100-seed weight and number of seedsper pod. In a line x tester study using malesterile lines, additivegeneeHects, werepredominant for inheritance of plant height.pods per plant, seed size, whereas, non ad 4i1ivegene effect appeared to be more importantlorother characters (Sidhu et a/. , 2000). Amongfemales, ms Prabhat (On was a good combinerfor early maturity, plant height, primarybranches, seeds/pod, seed size and grain yield.Ajaykumar et'a/. (2001) studied three geneticmale sterile lines and nine diverse testers ofearly duration and revealed that non-additiveglmetic variance chiefly controlled theexpression of yield/plant and attributes suchas primary branches, pods/plant, seed/pod,100-seed weight, whereas, additwe geneticvariance predominantly governed theexpression of days to 50% flowering and plantheight. Among male sterile lines ms PrabhatOT and illS Prabhat NOT were good generalcombiners and among testers ICPL 8'8001 wasbest general combiner for yield.

Stability of hybrids •The first pigeonpea hybrid ICPH 8

was released during 1991 by ICRISAT incollaboration with All India Coordinated PulsesImprovement Project of ICAR and is

recommended for cultivation in central zonecomprising Maharashtra, Madj1ya Pradesh andGujrat. The hybrid matures in 115-135 daysgiving a yield advantage of 41-52% over othervarieties in cultivation (Srivastava et a/. , 1994).However, a sigq.ificant impact is yet to benoticed on farmers field. Thus, much remainsto be done even after selecting a good heteroticcombinations. The factors such as stableperformance, environmental factors, improvedseed and pollen parents, resistance to prevalentdiseases and pests, seed production researchand on farm research have to be given dueemphasis in future research. Vanniarajan et'a/.(1997) noted that hybrids with high meanvalues for plant height, branches/plant, 100­seed weight and seed yield/plant were moreresponsive to favourable environments butunstable in changing environments.

. Manivel et aJ. (1998) studiedphenotypic stability of 40 hybrids and 14parents grown over three environments. Thehybrids, MS Prabhat NOT x Pant A2, MSPrabhat NOT x ICPL 161 and MS PrabhatNDT x DM1-5 were found stable under threefertility levels as they had high mean andregression coefficient not deviated from unityand non-significant, minimum deviation fromregression. Pandey and Singh (1998) notedsignificant hybrid x year interaction for seedyield. Bqth linear and non linear componentsof H x Y interaction played important role inthe expression of seed yield It was observedthat RAUPH 9117 and RAUPH 9003 wereadaptable to all environments, while the hybridRAUPH 9122 and RAUPH 9127 weresuitable for rich environments. Primarybranches and pods were the prime contributingcharacters to seed yield in short durationpigeonpea hybrids.

Genotype x environment interaction,effects were also assessed by Saxena et a/.(2001) for seed weight and grain yield of 12pigeonpea pea hybrids and lines viz.. (ICPH 8,

Vol. 2tJ. No.1. 2003 11

resistance. Gradual increase in the incidenceof macrophomina stem canker in late typesneccessitates adequate attention on this di:;ease.Rathnaswamy et al. (1998) observed that nohybrid was resistant either to pod borer or podfly. It was also noticed that the hybridsexhibiting pronounced incidence of pod borerrecorded lesser infestation of pod fly. Govil .etal. (2001) recorded genes for wilt and sterilitymosaic disease resistance besides male sterilityin two early maturing breeding lines viz., ICPL83024 (On x ICPL 86023 (IOn. These lineswere used as one of the parents in hybridbreeding programme in order to provideresistance in the hybrids besides yieldingcapacity.

Hybrid should also be tolerant to waterlogged conditions. Results revealed thattolerance was controlled by a major gene orgenes, but the variation in the diversity andthe length of adventitious roots andhypertrophied lenticals indicated that thetolerant reaction was also influenced by majorgene complexes (Perera et al., 1998).Pigeonpea hybrid COH-1 was tested with eighttreatments viz., inorganic Nand P, enrich,FYM, rhizobium seed treatment foliarapplication of OAP, NAA, KCL and variouscombinations of these. Results revealed thatthe highest grain yield (970 kg/hal wasrecorded when 25 + 50 kg N + P was appliedalongwith FYM @ 6t!ha (basqi) coupled with750 kg of enriched FYM apart 'from Rhizobiumseed treatment and foliar spray of 25 kg OAP/ha, twice.

In a study gypsum, .Pyrite,phosphogypsum, elemental sulphur and singlesuper phosphate as sources were applied onhybrids (Rajendra et ai, 1998). The resultsrevealed that, gypsum registered maximumplant dry matter production, leaf area index,plant height, pods/plant and grain yield.

In our efforts to bring stability in hybridproduction, we have to incorporate multiple

12 AGRICULTURAL REVIEWS

resistance to these adversities such as fusariumwilt, sterility mosaic, phytophthora blight as foras disease are concerned and pod borer,HelicoveJpa armigera, Maruca, pod fly are themajor insect-pest. Abiotic factors also play amajor role'in limiting production such as excessmoisture in rainy season and low temperatureat podding stage, Excess of salts in soil or wateralso affects the growth of plants. Long termprogrammes are necessary for theincorporation of genetic resistance to variousfactors as for as possible by Pyramiding thegenes. Biotic and abiotic stresses affect theyielding ability of hybrids as well as dependingupon the crop stages at which the crop issubjected to these stresses. In depthphysiological informati.on on controlmechanism(s) for these multi adversitiesvarieties can help in reducing their adverseeffects in target environments. Geneticalapproach based on physiological traits alongwitherripirical selection for yield is feasible forimproving the yield structure of hybrids intargeted environment.

Released hybrid in pigeonpeaICPH-8 is a first high yielding short

duration hybrid maturing in about 140 days. Itis indeterminate in growth habit and producesprofuse primary and secondary branches.ICPH-8 has also been found to perform wellunder drought conditions. It was developed byheterosis breeding in the cross MS Prabhat­DT x ICPL 169 at ICRISAT.

Another hybrid PPH-4 is released byPunjab Agriculture University, Ludhiana in1994 by using heterosis breeding in the crossMS Prabhat DT x AL 688, Hybrid plants showprofuse branching, 2.5 to 2.75 m. tall anddisease resistant. It matures in 145-147 days.Hybrid, IPH-732 is released by Tamil NaduAgriculture University, Coimbatore. It isdeveloped from the cross MST-21 x {CPL87109. The hybrid is of indeterminate growthhabit and matures in 115-120 days. It has good

cooking quality and 22% around protein.AKPH~410 1, a short duration hybrid has beenidentified for central zone of the country. It is aF

1hybrid of AKMS-4 x AK-101. The hybrid

has been found to have 64% superiority overUPAS 120 and 25% over ICPH-8. It hasindetermin~te flowering, semi spreadingbranches, medium bold, reddish brown seedsand matures in 140-145 days. The seeds havearound 21% protein and 70% dhal recovery.Its average 100-seed mass is 8.3 g.

Hybrid seed production in pigeonpeaMass transfer of pollen grains from

pollinator to male sterile line in pigeonpea iscaused by insects. In most places in India theextent of natural out crossing is sufficient toproduce abundance of hybridseeds on the malesterile plants. A distance of 300-400 meters isvery safe for producing seeds of hybrids as wellas of male sterile lines. The recommendedplanting ratio is 1 pollinator to 6 female rows(Saxena and Ariyanayagam, 1991). Plant thefirst row' with the pollinator parent, thereafter,repeat planting, 60 em apart, the pollinator atevery 7th row. The intra-row spacing should be10 em. The rows between the pollinator rowsshould be planted with the male sterile parentat a spacing of 10 em. Start roguing in themale sterile rows, as sterile plants will havewhite anthers and no pollen grains, while thefertile plants will have yellow anthers withabundance of pollen grains. The flowering inthe male sterile lines is spread over a 15-20days period. Roguing is an expensive operationand about 200 mandays will be required torogue one hectare land young pods developedin the pollinator rows should be removedperiodically to ensure continuous supply ofpollen grains for effective hybridization. Pickmature hybrid pods from the male sterile rowsonly. Besides the main crop, within a year, 2­3 ratoon crops can be harvested at the intervalof 45-50 days. Verma et al. (1993) observedthat removal of fertile plants from rows

Vol. 24, No.1, 2003 13

designated as females and MS ones from rowsdesignated as males at flowering ensured bettercontrol of seed quality. The seed formaintenance of the control of the MS line washarvested only from the maternal (MS) plants.Ravikesavan et al, 1995 worked out cost ofhybrid seed as Rs 67.9Ikg. However, hevisualized that cost of producing hybridpigeonpea seed could be brought down byincreasing the yield of hybrid seed.

Seedling markers in hybrid seed productionHybrids based on GMS have been

developed and released in India for cultivation..The effective hybrid seed production needsclear identifying dominant characters with eachparents. Efforts were, therefore, made to isolatedifferent seedling markers. S~me of them werederived from interspecific crosses, while otherswere from germplasm derived spontaneousmutations. Seven seedling markers viz., Green(I) Epicotyl (II) Broad long pair of plumulecov~ring leaves (110 Broad short pair of plumulecovering leaves (IV) Narrow short pair ofplumule covering leaves (V) unifoliate first leafafter the pair of plumule covering leaves (VI)Dark pigmented (brown) stem (VII) completegreen stem. These seedling markers have beenfixed and tl)eir genetic behaviour and linkagewith sterility gene is in progress (Patil, 1998).These seedling markers may be useful for fieldtest of hybrids and parents in future.

Ideal plant type concept in hybrid pigeonpeaCytoplasmic male sterile derived

hybrids of determinate and indeterminate habitwith few branches having small leaves withopen canopy, small pods and seed size around9-10 gl100 grains may be an ideal plant typein future hybrid. The immense geneticvariability available makes it possible to evolvehybrids with very early to extreme late, dwarfcompact to spreading plant type in future. Extraearly and early hybrids could find a niche as asole crop in areas with a seasonal rainfall of500-800 mm. The expected yield is 1 t-2 t

ha'l. The early types need about 14000C d and750°C temperature during vegetative andreproductive phases, respectively. The hybridcrop, could, therefore, fit into regions, wheremedium duration pigeonpeas are not g~~wnand replace crops such as maize, which havesimilar agroclimatic requirements.

Role of hybrids and its impact on socio­economic aspects

India is the land of agriculturists andthat 80 per cent of its population isagriculturally occupied. The fundamentalfunction of an agricultural department is toenable the farmer to produce food for peopleand raw material for industry from the soil aseconomically as possible. In recent decades,India has fortunately relied more on increasingthe yield potential of crop plants bydevelopment of hybrids or improving the plantstructure than on expansion of cropped areato' feed their populations. Therefore, someimportant points of socio-economic aspectsmaybe u6eful in adoption of pigeonpea hybrids.

• The response of hybrids to non-monetaryinputs viz., improved hybrid adoption,timely sowing, timely weeding, ridgeplanting etc. requires only the knowledgeon the utilization of the material inputs atthe right time and place and organizationskill of the growers.

• Human labour is the highest single costitem in present day pigeonpea hybridcultivation.

• The high annual fluctuations in prices ofpulses indicating a higher risk might haveturned the farmers away from pulses andin favour of other competing crops likeoilseeds and cereals, which exhibit lessprice fluctuations.

• The non-availability of seeds of highyielding varieties and hybrids in desiredquantity is the major constraint in theexpansion of pulses like pigeonpea.

• In pulses there are a number of diseases

14 AGRICULTURAL REVIEWS

and insect pests, which cause heavy lossesresulting in poor production even inhybrids.The area, production and productivity canbe increased to manifold, if the improvedtechnology, essential inputs and credit aremade available at proper time to the

farmers.'. Various constraints experienced by pulse

growers are the major cause of sharpdeclination of production, productivity andacreage of pigeonpea. Hence, there is anurgent need to channelize our efforts topopularize pulse crops among farmers.

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