CONIDIAL GERMINATION AND APPRESSORIUM FORMATION OF COLLETOTRICHUM-COCCODES ON TOMATO FOLIAGE

Conidial germination and infection processes of Colletotrichum coccode s were quantified on foliage of processing tomatoes (Lycopersicon escu lentum Mill.). The abaxial surface of two apposing terminal leaflets r emoved from a fully expanded leaf at the 4th to 5th node was inoculate d with 10-mu l droplets of C. coccodes conidial suspension. Leaflets w ere incubated for 2 to 24 h in 2-h intervals at 25 degrees C under hig h relative humidity. Explants with the conidial droplet were fixed, cl eared, and preserved for microscopic observation. The percentage of ge rminated conidia and those with unmelanized and melanized appressoria was determined for each leaf disk. Conidial germination increased line arly with time (R-2 = 0.73) (P = 0.001), maximizing (68.3%) 24 h after inoculation. The percentage of germinated conidia with unmelanized ap pressoria peaked 6 h after inoculation (38.3%). Melanized appressoria formation followed a linear trend (R-2 = 0.74) (P = 0.001), maximizing (62.0%) 24 h after inoculation. Infection vesicles were produced in 2 .7% of conidia by 22 h, indicating successful infection.