The aim of this study was to determine the antagonistic capacity of fungi to B. cinerea in blackberry crops in Costa Rica. During the first semester of 2009, 35 isolates of native filamentous fungi from the carpoplane of blackberry fruits were obtained, six of which belonging to the genus Trichoderma sp. were selected to evaluate their antagonistic effect in vitro against B. cinerea through the dual-culture technique. In this evaluation, competition for the substrate and the antibiotic effect were determined. The first one was calculated using Bell’s scale, and for the assessment of antibiotic effect, percent inhibition of radial growth (PIRG) was calculated. All tested isolates effectively competed for substrate against B. cinerea, within Trichoderma strains Lu13 and Lu15 excelled, achieving grade I in the scale used, where the antagonist overgrew the pathogen covering 100% of the culture medium. The remaining isolates of Trichoderma, were classified in grade II of antagonism. As to the antibiotic effect, all isolates inhibited mycelia growth of B. cinerea, four of which showed an effectiveness higher than 80% in this in vitro screening technique.
Keywords: gray mold, antagonistic test, Trichoderma, antibiosis.