STUDIES ON INTERACTION BETWEEN TRICHODERMA AND SOIL BORNE FUNGUS (Sclerotium rolfsii) AND ITS MOLECULAR BASIS
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Date
2015-04
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University of Agricultural Sciences Dharwad
Abstract
Sclerotium rolfsii is a soil borne fungal pathogen, which infects more than 500 crop species. Trichoderma spp. are being used effectively for the control of S. rolfsii. In the present study, both in vitro and in vivo assays were carried out to identify the potent Trichoderma isolate to suppress the S. rolfsii growth. The ten Trichoderma isolates studied behaved differently for different assays. Of the ten isolates, T. virens IABT1010 showed highest linear growth rate (19.75 mm/day) followed by T. viride IABT1044 (18.87 mm/day). However, in direct confrontation assay T. virens IABT1002 showed 100% growth inhibition of S. rolfsii. Similarly, for volatile substance assay, the isolate T. harzianum IABT1041 significantly inhibited the S. rolfsii, whereas chitinolytic activity was highest in T. virens IABT1002 (84.16 pmol/µg/min) and gluconolytic activity was high in T. viride IABT1044 (596.9 pmol/µg/min). In the in vivo assay, least seed rot infestation (55.55%) was observed in T. koningii IABT1252 treated Groundnut seeds compared to 100% in untreated seeds sown in S. rolfsii inoculated soil. The isolate, which performed better under in vivo experiment (T. koningii IABT1252) was selected for gene expression profiling in two stages of interaction viz., prior and after contact with S. rolfsii. The differentially expressed transcripts in both the stages were encoding for hydrolytic enzymes, secondary metabolites biosynthesis, transcription factors, signalling proteins, transporter proteins and protein involved in establishing the initial interaction. Of the 58 clones sequenced six did not show homology with any of the genes deposited in NCBI database. The differentially expressed transcripts by SSH was validated by profiling the expression pattern of few differentially expressed genes by qRT PCR study. The present study identified T. koningii IABT1252 as most potent, which needs to be studied further for its field performance. The identified genes, with mycoparasitic activity can be used to genetically engineer the crop plants in order to improve disease tolerance ability.
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