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Conidial Germination and Appressorial Formation of Colletotrichum capsid and C. gloeosporioides Isolates from Pepper. J. B. MANANDHAR, Research Fellow, International Rice Research Institute, P.O. Box 933,1099 Manila, Philippines. G. L. HARTMAN, Research Plant Pathologist, USDA, ARS, University of Illinois, Urbana 61801; and T. C. WANG, Associate Specialist, Asian Vegetable Research and Development Center (AVRDC), Shanhua, Tainan 741, Taiwan, ROC. Plant Dis. 79:361-366. Accepted for publication 19 December 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0361.

Conidial germination and appressorial formation of Colletotrichum capsici and C. gloeospori-oides were examined on pepper fruits and in association with some inorganic and organic compounds. Conidial germination and appressorial formation were greater on immature green or ripe red fruits of pepper (Capsicum annuum) variety Long Fruit than in water droplets on glass slides. Conidial germination was significantly (P = 0.05) higher for both fungi as concentrations of either sucrose or KCI increased. Appressorial formation for C. capsid was highest when sucrose was 10 mM and for C. gloeosporioides at 0.1 mM. Appressorial formation was reduced and mycelia formed for both fungi at higher sucrose concentrations, but not at 1-100 mM of KCI. Among six compounds tested for induced conidial germination and appressorial formation, CaCl2 and sucrose caused a significant (P 0.05) increase, KCI an intermediate one, and AlCl3 was lowest. β-resorcilic acid did not stimulate conidial germination and appressorial formation, and Fe-resorcilic acid stimulated conidial germination only for C. capsid. Three test melanin biosynthesis inhibitors at 1 g per milliliter stimulated conidial germination but varied in causing appressorial formation for both fungi. Appressorial formation of C. capsid was completely inhibited by tricyclazole and stimulated by fthalide and isoprothio-lane; appressorial formation of C. gloeosporioides was completely inhibited and stimulated by isoprothiolane and tricyclazole, respectively, and only slightly inhibited by fthalide. Inorganic and organic compounds that affect conidial germination and appressorial formation may play a role in the preinfection process of Colletotrichum spp. on pepper fruits.