Pre-penetration events and sporulation of Colletotrichum kahawae Waller and Bridge (SYA colletotrichum coffeanum Noack) on different cultivars of Coffea arabica

Abstract

Some components of resistance of C. arabica to C. kahawae were assessed by inoculation detached barriers and seedlings of six cultivars with 2x10** (6) conidia ml** (-1). Conidial germination and appressorial formation or epidermal walls of susceptible cultivars occurred within 4 h of inoculation compared to 30 h after inoculation on a resistant cultivar. A high percentage of appressorial formation was noted on epidermal walls of susceptible cultivars within 24 h of inoculation. Conidial germination and appressorial formation was greatly inhibited on epidermal walls of resistant cultivars. Sporulation of C. kahawae on susceptible cultivars occurred on the 3rd day after inoculation and by the 8th day, large necrotic depressions showing heavy sporulation had developed. Resistant cultivars showed inconspicuous dark brown lesions with very sparse sporulation on the 10th day after inoculation. The differences among cultivars, characterized by initial stagnation of pathogenesis and suppression of sporulation on resistant genotypes, could be related to resistance to C. kahawae