Mechanism of Biocontrol of Aspergillus flavus in Groundnut by Species of Trichoderma

Aflatoxin contamination of groundnut by Aspergillus flavus is a serious problem affecting the quality and commercial value of groundnut kernels. Biological management of A. flavus infection at pre- and post-harvest levels by using species of Trichoderma is a promising approach. Trichoderma isolates from the fields of Andhra Pradesh and Karnataka states of India were evaluated for their ability to control A. flavus (strain Af 11-4) in the laboratory. Out of 212 isolates of Trichoderma, 36 were potent antagonists and these were analyzed for the production of volatile and diffusible antibiotics. Twenty-one of the 36 isolates produced volatile antibiotics and 15 produced diffusible antibiotics. Biocontrol mechanism of their action was analyzed by estimating extracellular enzyme production viz, chitinase, protease and glucanase. Maximum chitinase activity was associated with the isolate T. viride (Tv 24), T. pseudokoningii (Tp 29) and T. harzianum (Th 42). T. harzianum showed a maximum protease activity while T. koningii (Tk 83) and T. longibrachiatum (Tl 102) produced glucanases in the presence of glucose