512 Transactions British Mycological Society

REFERENCES

BOEDIJN, K. B. (1929). Beitrag zur Kenntnis der Pilzftora von Sumatra. Recueil desTravaux botaniques nierlandais 26, 396-439.

DONK, M. A. (1965)' The mycological publications of K. B. Boedijn. Persoonia 3,325-33°.

GAMS, W. (1971). Cephalosporium-artige Schimmelpilze (Hyphomycetes). Stuttgart: G.Fischer Verlag.

EXPLANATION OF PLATE 47Acremonium hypholomatiJ

Fig. I. Conidiophores (x 650).Fig. 2. Conidiogenous cell with conidium (x 1000).Fig. 3. Conidia stained with cotton blue (x 1000).Fig. 4. Conidia stained with Giesma after N-HCI hydrolysis showing single nucleus (x 800).Fig. 5. Chlamydospores (x 1000).Fig. 6. Strands of hyphae from which conidiophores arise (x 1000).

Fig. 1-3 and 5-6 by Mr D. W. Fry; Fig. 4 courtesy of Dr D. E. Shaw.

INFLUENCE OF CONSTANT ANDFLUCTUATING TEMPERATURES ON THE GROWTH

OF MACROPHOMINA PHASEOLI

P. E. REYNOLDS, W. H. SMITH AND K. F. JENSEN*

Macrophomina phaseoli (Maubl.) Ashby (Sclerotium bataticola Taub.), animportant stem- and root-rotting pathogen, is thought to grow best athigh temperatures (Bega & Smith, 1960; Tompkins & Gardner, 1935).Diseases incited by this organism are assumed to be favoured in tropicalregions and in areas of high summer soil temperatures (Edmunds, 1964;Edmunds, Voigt & Carasso, 1964; Hodges, 1962; Livingston, 1945;Norton, 1953; Vaartaja & Bumbieris, 1967).

The relationships between organisms and the temperaturel> of theirenvironments is extremely complex. One of the most important aspectsof this relationship is the differential influence of fluctuating and constanttemperatures (Jensen & Reynolds 1969). The degree and significance ofthis differential response has been discussed for M. phaseoli by Smith (1964).The isolate (R-3, isolated 1959) used by Smith (R. S. Smith, Jr., Pac.S.W. Forest and Range Exp. Sta., Berkeley, California) was obtained andemployed in the present study along with a recent isolate (A-I, isolated1970) obtained from the same California forest tree nursery and isolate(A-2) acquired from the American Type Culture Collection (No. 14380).

* Graduate Student and Assistant Professor of Forest Pathology, respectively, School ofForestry, Yale University, New Haven, Connecticut, 06511 and Research Plant Physiologist,Forest Insect and Disease Laboratory, U.S. Forest Service, Delaware, Ohio, 43015. Thisinvestigation was supported by the National Science Foundation, Grant Number GB-21252.

Trans. Br. mycol. Soc. 58 (3), (1972). Printed in Great Britain

Trans. Br. mycol. Soc.

1

3

2

Vol. 58 Plate 47

4

6

(Facing p. 512)

80 ,..----,1,..----,1,..----,,..-----,----,1----,

Notes and Brief Articles90 ,--,---,---,---,---,-------,

---- After 48 hMean 30-

" /JI... .....70 ~

-0---0- After 24 hXO /JI-----_//_ ...._~,,-_-.

E 60 ""', E 70 / /{/ "1§ I - ... , g / A'/ '- Mean 25"I ............ / --..c:: ~ /_--

~I

~ 60~'"50 I o V2 IeIJ I 5b Mean 30 -:- I :- 503 40 I - (J ,v I ';JE I E

~.~ 30 ) .~ 40"':l - "':l/'

/'V \(J

/'OIl OIl

2

~'" -Mean 25~

20 "- - :- 30(J (J

>~ <C

10 20 ---- After 48 h~After24h

o 1 I 1 I I 10 L.._L.----..lL.....----l_.......I._----I..._--l

15 20 25 30 35 0 6 12 18

Constant temperature 0 Range of temperature fluctuation (')

Fig. 1 Fig. 2

Fig. I. Average colony diameter of Macrophomina phaseoli, isolate R-3 grown on potatodextrose agar at various constant temperatures after 24 and 48 h of growth.Fig. 2. Average colony diameter of Macrophomina phaseoli, isolate R-3 grown on potatodextrose agar at various fluctuating temperatures after 24 and 48 h of growth.

This latter isolate has been maintained in a freeze-dried or frozen condi­tion.

The growth response of M. phaseoli was measured in an incubatorequipped with a cam-type temperature programmer. Constant-tempera­ture treatments were 15, 20,25, go and S5 ± 1°. Fluctuating temperatureregimes had ranges of fluctuation of 6, 12 and 18° around means of 25°and soo. The isolates were grown on potato-dextrose agar in Petri plates,inoculated by cutting an agar plug from the edge of an actively growingculture with a cork borer and inverting the plug in the centre of a plate.After 24 or 48 h of temperature treatment the mean diameter of eachculture was determined by measuring the colony diameter at two loca­tions, at right angles to each other. The temperature regimes werereplicated twice. Each replication contained four plates.

Growth produced by R-g after 24 and 48 h at constant temperaturewas greatest at 25° (Fig. I), but growths at 25° and goO did not significantlydiffer at the I % level.

Growth produced by R-S after 24 h of fluctuating temperature wassignificantly greater at both means and at all amplitudes of fluctuationthan growth at the constant temperatures. The greatest growth after 24 hwas produced at So ±3° (Fig. 2). Measurements made after 48 h revealeda somewhat altered pattern. Growth at 25 ± gO, for example, was notsignificantly different from that at the constant temperature of 25°. Thegreatest growth at 48 h was recorded by those cultures grown at 25 ±6°.

Trans. Br. mycol. Soc. 58 (3), (1972). Printed in Great Britain

Transactions British Mycological Society

15 20 25 30Con;,lant temperature CO)

35

Fig. 3. Average colony diameter of Macrophomina pluzseoli, isolate R-3 (isolated fromCalifornia forest tree nursery in 1959), isolate A-I (isolated from same Californiaforest tree nursery as R-3 in 1970) and isolate A-2 (obtained from American TypeCulture Collection, no. 14380) grown on potato dextrose agar at various constanttemperatures after 24 h of growth.

Smith (1964) found that the constant temperature of 35° was optimalfor linear growth of isolate R-3, while our data indicate 25° to be mostfavourable. With respect to fluctuating temperatures, Smith claimed thatamplitudes greater than 2'2° (4°F) decreased growth rate at a mean of25°. Our data suggest that a fluctuation amplitude of 6° around a meanof 25° is stimulatory to the growth of isolate R-3. Isolates A-I and A-2were therefore investigated.

When isolates A-I and A-2 were exposed to our five constant tempera­tures, maximal growth (after 24 h) was obtained at 35°, consistent withSmith's original findings (Fig. 3). Preliminary experiments just completedon the pathogenicity ofisolate R-3 indicate a slight attenuation ofvirulenceover that demonstrated in a previous experiment (Smith, 1969).

During the approximate 7-year period since Smith's original experi­ments were performed, isolate R-3 has been maintained under coolrefrigeration (4°) on agar slants. If variation in temperature responseexists in the organism, selection may have operated in favour of hyphaeor spores more adapted to lower temperatures.

If temperature is the primary factor, or one of the primary factors,which restricts the present significance of M. phaseoli as a pathogen incool temperature regions, then capacity to develop vigorously at lowertemperatures as indicated in this study may suggest the potential for in­creased pathogenicity in cooler areas.

The difference in growth between constant and fluctuating temperatureregimes and between various isolates indicate that temperature data must

Trans. Br. mycol. Soc. 58 (3), (1972). Printed in Great Britain

Notes and Brief Articles 515be very carefully interpreted and that considerably more study is requiredto increase our understanding of temperature relationships.

REFERENCES

BEGA, R. V. & SMITH, R. S. (1960). Diseases threaten forest nurseries. Pacific South WestForestry and Range Experimental Station, Miscellaneous Paper no. 52. 3 pp.

EDMUNDS, L. K. (1964)' Combined relation of plant maturity, temperature, and soilmoisture to charcoal stalk rot development in grain sorghum. Phytopathology 54,5 14-5 17.

EDMUNDS, L. K., VOIGT, R. L. & CARASSO, F. M. (1964-). Use of Arizona climate toinduce charcoal rot in grain sorghum. Plant Disease Rep()rter 48, 300-302.

HODGES, C. S. (1962). Black root rot of pine seedlings. Phyt()patwlogy 52, 21lHH9.JENSEN, K. F. & REYNOLDS, P. E. (1969). How two types of fluctuating temperature

affect the growth of Fusarium s()lani. North East Forestry Experimental Statiqn, ResearchNote NE- I05· 4 pp.

LIVINGSTON, J. E. (1945). Charcoal rot of corn and sorghum. Research Bulletin of theNebraska Agricultural Experimental Station no. 136. 32 pp.

NORTON, D. C. (1953)' Linear growth of Sclerotium bataticola through soil. Phytopatwlogy43, 633-636.

SMITH, R. S., JR. (1964). Effect of diurnal temperature fluctuations on linear growthrate of Macrophomina phaseoli in culture. Phytopathology 54, 849-852.

SMITH, W. H. (1969). Comparison of mycelial and sclerotial inoculum of Macrophominaphaseoli in the mortality of pine seedlings under varying soil conditions. Phyto­pathology 59, 379-382.

TOMPKINS, C. M. & GARDNER, M. W. (1935). Relation of temperature to infection ofbean and cowpea seedlings by Rhizoctonia bataticola. Hilgardia 9, 219-230.

VAARTAJA, O. & BUMBIERIs, M. ([967). Organisms associated with root rots of conifersin South Australian nurseries. Plant Disease Reporter 51, 473-4-76.

FUNGI ISOLATED FROM SURFACE-STERILIZEDTOBACCO LEAVES

D. NORSE

Chitedze Agricultural Research Station, Lilongwe, Malawi*

The presence of Colletotrichum species has frequently been detected inapparently healthy tissues. Shear & Wood (1913) found species ofColletotrichum and Glomerella in apparently healthy leaves, stems, flowersand fruits of many plants after surface sterilization. Latent infections ofC. gloeosporoides are established in a wide range of tropical fruits soon afterfruit set, and visible symptoms do not appear until the later stages ofripening (Baker, 1938).

In a more recent study a wide range of fungal genera were isolatedfrom mature tobacco leaves which were either symptomless or carriedbrown spot lesions caused by Alternaria longipes (Ell. & Ev.) Mason (Welty,Lucas, Fletcher & Young, 1968). The most common genera found wereAlternaria, Cladosporium, and Epicoccum. Latent infections of Alternarialongipes have been detected in tobacco leaves as early as 7 days afteremergence (Norse, 1971). During the latter study other fungi were

• Present address: Imperial College Field Station, Silwood Park, Sunninghill, Berks.

Trans. Br. mycol. Soc. 58 (3), ([972). Printed in GreaJ Britain