EFFECTS OF CALCIUM AND CALMODULIN ON SPORE GERMINATION AND APPRESSORIUM DEVELOPMENT IN COLLETOTRICHUM-TRIFOLII

Spore germination and appressorium formation are important steps in th e process of fungal development and pathogenesis. These prepenetration events, which begin with spore attachment and culminate with appresso rium maturation, a common scheme for many pathogenic fungi, are prereq uisites for penetration of host external barriers and subsequent colon ization. Conditions for in vitro spore germination and appressorium de velopment in Colletotrichum trifolii are described. In addition, effec ts of Ca2+ and calmodulin on these processes have been examined, Resul ts indicate that, as for other pathogenic fungi, appressorium developm ent is induced on a hard surface, The data suggest that disturbance of calcium homeostasis, by ethylene-bis(oxyethylenenitrolo)tetraacetic a cid (EGTA) or calcium channel blockers, impairs appressorium developme nt, Moreover, calmodulin inhibitors affect both germination acid diffe rentiation, implying that the Ca2+/calmodulin signal transduction path way is important in the early development of C, trifolii on the plant host surface.