Biocontrol potentials of native bacterial strains for the management of coffee berry disease (Colletotrichum kahawae) in Ethiopia

Coffee berry disease (CBD) is a calamitous anthracnose of green berries of Coffea arabica L. caused by a fungal pathogen Colletotrichum kahawae Waller & Bridge. Coffee yield losses reach 80-100% on susceptible cultivars if effective control is not properly implemented. The antagonistic potential of 23 native bacterial strains, collected from Arabica coffee tree, was assayed against the fungus under in vitro and in vivo conditions. The strains were first tested for their antifungal activities on mycelia growth inhibition and suppression of conidia germination. Those promising strains were further evaluated for disease reduction and biocontrol efficacy in detached green berries and seedling hypocotyls of highly- and moderately- susceptible coffee cultivars. Among others, Bacillus cereus ECk-03, B. megaterium ECk-05, B. mycoides ECk-06, and Pseudomonas spinosa ECk-17 showed significantly (P < 0.05) greater mycelia growth inhibition (67-87%) and higher suppression of conidia germination (85-90%). The infection of berries and seedling hypocotyls by C. kahawae were almost prevented and thereby significantly (P < 0.05) reduced severity of CBD (>75-80%) was achieved in highly and moderately susceptible coffee cultivars 'cv. 370' and 'cv. 74110' treated with Bacillus megaterium ECk-05, B. mycoides ECk-06 and P. spinosa ECk-17. The strains demonstrated the highest CBD reduction and pronounced biocontrol efficacy (>70%) at 48 h pre-fungal inoculation. The consistent performance of Bacillus megateriumECk-05, B. mycoidesECk-06 and P. spinosaECk-17 strains in antifungal activities and higher disease reduction suggest as potential biocontrol for the management of CBD encouraging organic coffee production.