| Summary: | Forty-two Trichoderma isolates were characterized using various molecular and morphological approaches. Morphological identification using conidial and growth characters did not provide sufficient information for reliable species identification. ITS sequences clearly separated all the biocontrol isolates from the pathogenic isolates of T. harzianum. Endochitinase gene sequence based analysis of the isolates revealed similar pattern of grouping to that of ITS except for two isolates (Tv 2 and TRC 1), whereas beta-tubulin gene phylogeny resulted in a better resolution of the isolates belonging to the section Pachybasium. Isolates belonging to Trichoderma sections Trichoderma and Longibrachiatum grouped similarly when analyzed by ITS, endochitinase and beta-tubulin sequences. Though morphological and ITS sequence analysis differentiated pathogenic isolates from biocontrol isolates of Trichoderma, the endochitinase and beta-tubulin genes did not, presumably due to the functional nature of these genes in the fungus. Significant differences were observed in biocontrol efficacy when Trichoderma isolates were applied against Fusarium culmorum in wheat. No correlation was observed between biocontrol efficacy and phylogenetic relationship of the isolates. Significant growth enhancement was observed when Trichoderma was applied to the soil. Antagonistic mixtures performed poorly when compared to individual application of the biocontrol isolates. Genetic diversity inferred from ISSR data revealed a high level of inter- and intra-specific variability. All isolates clustered into 27 different groups distributed into six clusters. Sequence variations observed in endochitinase gene and ITS regions were successfully used for development of strain- and species-specific primers with a very high level of specificity and sensitivity of down to l0pg/μ1 of DNA concentration in conventional end-point PCR. The study reveals the efficiency of molecular markers for species identification and explores the genetic diversity among the isolates and their impact on biocontrol efficacy.
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