Variation among colletotrichum isolates associated with coffee berry disease in Ethiopia

Variations among the populations of Colletotrichum species from diseased coffee berries were studied. A total of 35 Colletotrichum isolates representing 24 districts from major coffee-producing regions of Ethiopia was studied on the basis of cultural, morphological, and pathological characteristics. The isolates differed significantly on their colony color, density, sector, and acervuli. Mycelial growth rate varied significantly (p < 0.05) among the isolates and ranged between 3.97 and 8.69 mm/day. Sporulation capacity, conidial length (12.3–17.7 μm) and conidia width (3.6–5.1 μm) also varied significantly (p < 0.05) among the isolates. The dominant forms of conidia were cylindrical and round at both ends followed by cylindrical acute at one and round at the other ends. Cluster analysis based on cultural, morphological, and pathological characteristics showed that isolates of Colletotrichum species associated diseased coffee berries fell into three distinct groups and were identified as C. kahawae, C. gloeosporioides, and C. acutatum. Among these fungal isolates, only C. kahawae was pathogenic to both detached coffee berries and coffee hypocotyls tested. The other Colletotrichum species exist as saprophytic or sequential colonizer of dead tissues. In conclusion, our study indicates the existence of variation in cultural, morphological characteristics and pathogenicity among the C. kahawae and the other related Colletotrichum isolates. However, molecular methods and other detail biochemical tests would provide the genetic diversity of the CBD pathogen populations in the country.