Molecular and morphological characters: An appurtenance for antagonism in Trichoderma spp.
Biocontrol agent Trichoderma has attained importance for substitute of chemical pesticides and hence an attempt was intended to corroborate the positive relatedness of molecular and morphological characters with antagonistic ability. Twelve isolates belonging to Trichoderma harzianum and Trichoderma viride were assessed for their mycoparasitic effect on phytopathogens Pythium aphanidermatum and Sclerotinia sclerotiorum. Though T. harzianum isolates were more aggressive than T. viride isolates, the percent inhibitory effect among T. harzianum isolates did not vary much (80 to 86%). The inhibitory effect of T.viride isolates ranged from 50 to 80%; however, TvChen, Tv4, and TvNir were distinguishable from other T. viride isolates in exhibiting higher degree of antagonism. The dataset generated through morphological characters and molecular markers (RAPD and ISSR) showed a comparable output grouping the isolates Tv4, TvChen and TvNir in one cluster and all T. harzianum isolates in another cluster. Multiple nucleotide alignment of ITS 1 and ITS 2 region produced 100% homology among T. harzianum isolates whilst the nucleotide substitution at 62nd and 150th position of ITS 1 region and 27th and 40th position of ITS 2 region differentiated Tv4, TvChen and TvNir from other T. viride isolates. Genetic assessment could not establish substantial disparity among T. harzianum isolates which was comparable with its antagonism. The genetic distinctness of Tv4, TvChen and TvNir isolates authenticated their higher degree of antagonism. It is obvious from the present study that genetic diversity analysis had a positive correlation with the antagonistic ability of Trichoderma isolates. Thus an integrated approach of morphological and molecular markers can be employed to identify a superior strain of Trichoderma for its commercial exploitation.
Key words: Trichoderma, antagonism, morphological and molecular characters, RAPD, ISSR, ITS.