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Pursuit of Native Fungal Biocontrol Agent Trichoderma for Nepal and Ohio

Ram B. Khadka: Department of Plant Pathology, The Ohio State University

<div>Experiments were conducted to assess the biocontrol mechanisms of 39 <em>Trichoderma</em> isolates from diverse microclimatic domains in Nepal and Ohio, USA. <em>Trichoderma</em> species identified by internal transcribed spacer gene sequencing were: <em>T. asperellum </em>(n=15), <em>T. koningiopsis</em> (n=15), <em>T. harzianum </em>(n=3), <em>T. ovalisporum</em> (n=2), <em>T. cerinum </em>(n-1), <em>T. citriviride </em>(n-1), <em>T. hamatum </em>(n=1) and <em>T. ghanense </em>(n-1). Standard agar plate assays were conducted to evaluate growth inhibition by <em>Trichoderma</em> isolates of <em>Rhizoctonia solani</em>, <em>Phytophthora capsici </em>and <em>Pythium ultimum</em> by competition, mycoparasitism, and antibiosis through production of volatile and non-volatile inhibitors. The efficacy of these isolates in suppressing radish root rot caused by <em>R. solani</em> was tested under greenhouse conditions. Four isolates of <em>T</em>. <em>koningiopsis</em> (T-17, T-28, T-29 and T-3) showed more than 60% inhibitory activity against the pathogens by volatile metabolites. Two isolates each of <em>T. asperellum</em> (T-18, T-30) and <em>T. koningiopis</em> (T-29, T-25) inhibited pathogen growth through non-volatile metabolites by more than 50%. Six isolates of T. <em>koningiopsis</em> (T-25, T-1, T-16, T-21, T-22, and T-8) and two isolates of <em>T. asperellum</em> (T-27, T-30) outperformed the others in confrontation and <em>in planta</em> experiments. The majority of the effective <em>Trichoderma</em> isolates were recovered from tropical and subtropical climates in Nepal. These isolates merit further evaluation for biocontrol and other industrial applications.</div>