Characterization of Trichoderma spp. antagonistic to Phytophthora colocasiae associated with leaf blight of taro

Eighteen Trichoderma strains isolated from soils of different regions of India were analyzed for their biocontrol potential against the taro leaf blight pathogen Phytophthora colocasiae. The strains were characterized using a combination of phenotypic and molecular approaches, viz., in vitro antagonism, extracellular enzyme production, ITS and tef1 gene sequencing and AFLP analysis. Eight isolates exhibited more than 75 % inhibition of the pathogen P. colocasiae. Differential antagonistic activity was evident for different strains. Assay of lytic enzyme production suggested the role of glucanase in mycoparasitism of P. colocasiae. Sequencing and phylogenetic analysis of the Trichoderma strains showed that isolates belong to three species: Trichoderma asperellum, Trichoderma longibrachiatum and Trichoderma harzianum. AFLP analysis revealed profound genetic diversity among the isolates. The most potent strain overall (TR7) identified as T. harzianum was able to control P. colocasiae in vivo also. This isolate could be used as a promising candidate for biological control of taro leaf blight disease.