Factors affecting appressoria formation by Colletotrichum corchori

Notes and brief articles species at this critical temperature. This has been postulated as the primary reponse of sen sitive species to chilling temperatures and is thought to lead to changes in membrane permeability and in the activity of membrane-bound enzymes with the accumulation of toxic intermediates and hence damage or even death of cells (Lyons, 1973). It is, therefore, of interest that Matsumoto, Buckley, Sommer & Shalla (1969) observed membrane disorganization, particularly of the mitochondria, of chilled sporangiospores of R. stolonifer, Similarly Madelin & Ogunsanya (1979) conclude that cell lipids and cytoplasmic membrane systems may be involved in chilling sen sitivity of conidia of B. ricinicola.

This work was carried out during J. Hocker's industrial training from the Department of Food Science, Agricultural University, Wageningen, The Netherlands. The authors would like to thank Professor J. M. Ogawa for cultures of R. arrhizus and R. oryzae. REFERENCES

DENNIS, C. & BLIJHAM, J. M. (1980). Effect of temperature on viability of sporangiospores of Rhizopus and Mucor species. Transact ions of the British My cological Society 74, 89-94. LYONS, J. M. (1973). Chilling injury in plants. Annual Review of Plant Phy siology 24, 445-466. LYONS, J. M. & RAISON, J. K. (1970). Oxidative activity of mitochondria isolated from plant tissues sensitive and resistant to chilling injury. Plant Physiology 45, 386-389.

MADELIN, M. F. & OGUNSANYA, O. C. (1979). The fine structure of conidia of Botryodiplodia ricinicola with observations on chilling. Annals of Botany 44, 417-425. MAHESHWARI, R. & SUSSMAN, A. S. (1971). The nature of cold-induced dormanc y in urediosporesof Puccinia graminis var. trit ici. Plant Phys iology 47, 289-295. MATSUMOTO, T. T., BUCKLEY, P. M., SOMMER, N. F. & SHALLA, T. A. (1969). Chilling-induced ultrastructural changes in Rhizopus stolonifer sporangiospores. Phytopathology 59, 863-867. MATSUMOTO, T. T. & SOMMER, N. F. (1967). Sensitivity of Rhizopus stolonifer to chilling. Phytopath ology 57, 881-884· O'BRIEN, F. E. M. (1948). The control of humidity by saturated salt solutions. Journal of Scientific In struments 25, 73-76. OGUNSANYA, O. C. & MADELIN, M. F. (1977). Sensitivity of Botryodiplodia ricinicola conidia to mild chilling. Transactions of the British Mycological Society 69, 191-195. SMITH, W. L., MILLER, W. M. & BASSETT, R. D. (1965). Effect of temperature and relative humidity on germination of Rhizopus stolonifer and Monilinia fructicola spores. Phytopathology 55, 604-606. T EITELL, L. (1958). Effects of relative humidity on viability of conidia of aspergilli. American Journal of Botany 45, 748-753. UDUEBO, A. E. & MADELIN, M . F . (1974). Germination of conidia of Botryodiplodia theobromae in relation to age and environment. Transactions of the British Mycological Society 63, 33-44. WEXLER, A. & HASEGAWA, S. (1954). Relative humidity -ternperature relationships of some saturated salt solutions in the temperature range 0° to 50 °C. Journal of Research of the National Bureau of Standards 53, 19-26.

FACTORS AFFECTING APPRESSORIA FORMATION BY COLLETOTRICHUM CORCHORI R. P. PURKAYASTHA AND USHA

MENON

D epartment of Botany, University of Calcutta, Ca!cutta-700019, India Colletotrichum corchori Ikata & Tanaka, associated with anthracnose disease of jute (Corchorus capsularis L.) causes much damage in India and other jute-growing countries. The initiation, formation and action of the appressoria are integral parts of the infection process (Emmett & Parbery, 1975) and a clear understanding of these structures and the factors associated with their formation is necessary for a detailed study of the disease. In this investigation the behaviour of Colletotrichum spores towards susceptible, resistant and non-host cultivars was studied, together with the effect of Tran s. Br. my col. Soc. 77 (1), (1981).

some physical and chemical factors on appressoria formation. To study appressoria formation on artificial substrates drops of the spore suspension were mounted on glass slides and incubated for 24 h under various conditions, after which they were stained with cotton blue in lactophenol and exam ined microscopically. Standard drops of spore suspension were also placed on leaf surfaces and incubated for 24 h under moist conditions. Percentage germination and appressoria formation on leaf surfaces were

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Notes and briefarticles calculated after decolorization following the standard technique of Janes (1962) and staining with cotton blue. The leaf exudates were obtained by placing water drops on the leaves for a period of 24 hand then collected, combined and assayed as described by Purkayastha & Deverall (1965). The results showed that both germination and appressoria formation were optimum at 25°C. The spores germinated and appressoria formed over a wide range of temperatures (20-40°) and pH values (4-8), and there were more appressoria formed with increase in pH values up to 8. Spore germination started after 4 h incubation and appressoria were observed after 16 h. Germination of spores was better in light than in darkness and appressoria formation increased up to an optimum light period (10 h), beyond which there was a reduction. Ishida & Akai (1969) observed that the optimum temperature for appressoria formation in C. lagenarium varied from 20-26°, while 22° was recorded for C. gloeosporioides (Purkayastha & Sen Gupta, 1973). Probably there are many factors making up the 'conducive environment' for appressorium formation in particular species (Emmett & Parbery, 1975). There is evidence that in Puccinia helianthi the decrease in appressoria at increased light intensity was overcome by exposure to alternate periods of light and dark (Sood & Sackston, 1972). Ten phenolics (phloroglucinol, resorcinol, catechol, vanillin and picric, gallic, phthalic, salicylic, tannic and benzoic acids) were tested for their effects on appressoria formation. Most compounds had little inhibitory effect, but 100 p.p.rn. vanillin and tannic acid reduced appressoria formation significantly (17"1 and 11'2 % respectively, compared with 84'9 % in the water control). This substantiates the earlier findings of Srinivasan & Narasimhan (1971) that vanillic acid, ferrulic acid, p-salicylic acid and p-coumaric acid decreased appressoria formation in C. falcatum, Appressoria formed on the leaf surfaces (Table 1) and in the leaf exudates (Table 2) of two jute cultivars (D-154 and JRC 412) and one soybean cultivar (Soymax) as well as on glass slides, but the percentage of appressoria formation was significantly less on the resistant cultivar. The differences in the other three treatments were insignificant. Electromagnetic radiations such as ultraviolet light, X-rays and y-rays have been used to control various fungal diseases by killing the pathogens, and in some cases satisfactory results have been obtained (Agrios, 1978). An attempt was, therefore Trans. Br. mycol, Soc. 77 (1), (1981).

made to ascertain how X-rays affect appressoria and spore germination of C. corchori. Results suggested that doses of up to 500 r are inhibitory to both processes. Leath & Rowell (1970) showed that Puccinia graminis formed appressoria equally well on both host (wheat) and non-host (corn) but they did not compare the resistant and susceptible cultivars. Similar results were also obtained with Erysiphe graminis and E. cichoracearum by Staub, Dahmen & Schwinn (1974) and Heath (1972) observed that appressoria were formed more or less equally on both resistant host and non-host cultivars by Uromyces phaseoli var. vignae. This observation does not agree with the results of the present study since a marked difference in appressoria formation has been observed between resistant host (D-154) and non-host (Soymax) cultivars. Suppression of appressoria formation on resistant host leaves or in leaf exudates may be due to the presence of an inhibitor in the resistant cultivar and the isolation

Table 1. Effect of leaf surface on appressoria formation by Colletotrichum corchori Percentage Germappressoria tube Percentage formation length Substrate germination ±S.E. Cum) Jute JRC 412 56 (susceptible) 21'3±O,8

D- 154

(resistant) Soybean (non-host) Glass slide

88'S

59

43

Table 2. Effect of leaf exudates on appressoria formation by Colletotrichum corchori

Exudate from Percentage leaves of germination Jute JRC 412 (susceptible) D- 154

93'2

Percentage appressoria formation

Germtube length

±S.E.

(jlm)

49 13'2±o,g

22

(resistant) Soybean (non-host)

95'S

55

Glass slide

97'3

47

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Notes and brief articles and characterization of this compound may give some insight in understanding the mechanism involved in the suppression of appressoria formation on resistant hosts. REFERENCES

AGRIOS, G. N. (1978). Plant Pathology. Academic Press: New York and London. EMMETT, R. W. & PARBERY, D. G. (1975). Appressoria. Annual Review of Phytopathology 13, 147-167. HEATH, M. C. (1972). Ultrastructure of host and nonhost reactions to cowpea rust . Phytopathology 6:2, 27-38. ISHIDA, N. & AKAI, S. (1969). Relation of temperature to germination of conidia and appressoria formation in Colletotrichum lagenarium. Mycologic 61, 382386. JANES, B. S. (1962). Leaf clearing technique to assist fungal spore germination counts. Nature, London 193, 1099- 1100. LEATH, K. T. & ROWELL, J. B. (1970). Nutritional and inhibitory factors in the resistance of Zea mays to Puccinia graminis . Phytopathology 60, 1097-1100.

PURKAYASTHA, R. P. & DEVERALL, B. J. (1965). The detection of antifungal substances before and after infection of beans (Vicia faba L.) by Botrytis spp. Annals of Applied Biology 56, 269-277. PURKAYASTHA, R. P. & SENGUPTA, M . (1973). Studies on conidial germination and appressoria formation in Colletotrichum gloeosporoides Penz. causing anthracnose of jute (Corchorus olitorius L.). Zeitschrift fur Pjlanzenkrankheiten und Pfianzenschutz 80,718-7 24. SOOD, P. N. & SACKSTON, W. E. (1972). Studies on sunflower rust. XI. Effect of temperature and light on germination and infection of sunflower by Puccinia helianthi, Canadian Journal of Botany 50, 1879- 1886. SRINIVASAN, K. N. & NARASIMHAN, R. (1971). The effect of certain phenolic and related compounds on spore germination and appressorium formation in Colletotrichum [alcatum , Proceedings of Indian Academy of Science 73, 81-91. STAUB, T., DAHMEN, H. & SCHWINN, F. S. (1974). Light and scanning electron microscopy of cucumber and barley mildew on host and non-host plants. Phytopathology 64, 364-372.

PRODUCTION OF AL TERNARIOL AND AL TERNARIOL MONO METHYL ETHER AND MORPHOLOGY OF ALTERNARIA ALTERNATA P. HAGGBLOM

Institute of Physiological Botany, University of Uppsala, S-751 21 Uppsala, Sweden Alternariol (AOH ) and alternariol monomethyl ether (AME) are toxic secondary metabolites produced by strains of Alternaria alternata (Harvan & Pero, 1976) and have been isolated from such commodities as decaying tomatoes (Harwig, Scott, Stoltz & Blanchfield, 1979) and sorghum (Burroughs, Seitz, Sauer & Mohr, 1976). In papers where production of AOH and AME were followed on natural (Burroughs et al., 1976) or artificial substrates (Hult & Gatenbeck, 1976, 1978) the hyphal or mycelial morphology of the cultures was never discussed. During previous work with light inhibition of AOH and AME production in A. alternata (Haggblorn & Unestam, 1979) it was noted that a producing strain, maintained as stock culture, spontaneously lost most of its ability to produce AOH and AME after several transfers. In this work I have studied the changed morphology of this genetically altered strain of A. alternata in relation to decreased production of AOH and AME. Trans. Br. mycol. Soc. 77 (1), (1981).

Alternaria alternata (Fr.) Keissl., strain IMI 89343, Commonwealth Mycological Institute, Kew, Surrey, England (toxin-producing) and a low-producing strain of A . alternata, isolated after several transfers from the producing strain, were cultivated on liquid modified Czapek-Dox medium (Gatenbeck & Sierankiewicz, 1973). Stock cultures were kept in darkness at 4 °C in 50 ml bottles containing 15 ml of modified Czapek-Dox medium with 1'5 % agar (Difco). Inoculation techniques and cultivation are described by Haggblom & Unestam (1979). Dry weights of mycelia were determined after drying for 24 h at 105°. Extraction, separation, and qualitative and quantitative analysis of AOH and AME were made according to Haggblom & Unestarn (1979). The TLCplates were developed by the method of Hult & Gatenbeck (1976). After consecutive transfers it was observed that the AOH and AME producing strain had lost its toxin-producing ability almost completely. Cul-

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