Identification of Trichoderma species and their antagonistic potential against Aspergillus flavus in groundnut

The antagonistic potential of 212 Trichoderma isolates, obtained from soil samples collected from 4 districts in Andhra Pradesh, India, and 2 districts in Karnataka, India, against a highly aggressive and toxigenic strain of A. flavus (Af 11-4) was investigated. One-hundred and forty-five isolates were antagonistic to Af 11-4. Among these, only 39 showed clear inhibition zone against Af 11-4. These isolates were identified and further evaluated for antagonism, involving production of volatile and non-volatile antibiotics, and hyphal interaction with Af 11-4. The 39 isolates were classified into 6 groups: T. harzianum (11), T. hamatum (1), T. viride (9), T. longibrachiatum (5), T. koningii (9), T. pseudokoningii (3); and unknown species, based on morphological traits and inhibition zone against Af 11-4. Twenty-one isolates showed inhibition of Af 11-4 colony by producing volatile antibiotics compared with the control. Among the isolates, T 102 (T. longibrachiatum) showed the maximum inhibition. Fifteen isolates showed inhibition of Af 11-4 colony by producing diffusible antibiotics compared with the control. Isolate T 29 (T. pseudokoningii), T 42 (T. harzianum), and T 83 (T. koningii) showed significant inhibition of Af 11-4 growth. Examination under microscope for hyphal interactions showed that isolates T 16 (T. viride), T 109 (T. harzianum), and T 188 (T. viride) showed clear hyphal coiling with Af 11-4 mycelia