Abstract
Endophytic Trichoderma hamatum UoM 13 isolated from pearl millet roots was evaluated for its efficiency to suppress downy mildew disease. Under laboratory conditions, T. hamatum seed treatment significantly enhanced pearl millet seed germination and seedling vigor. T. hamatum seed treatment resulted in systemic and durable immunity against pearl millet downy mildew disease under greenhouse and field conditions. T. hamatum treated seedlings responded to downy mildew infection with high lignification and callose deposition. Analysis of defense enzymes showed that T. hamatum treatment significantly enhanced the activities of glucanase, peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase in comparison to untreated control. RT-PCR analysis revealed differentially expressed transcripts of the defense enzymes and PR-proteins in treated, untreated, and checks, wherein PR-1, PR-5, and cell wall defense HRGPs were significantly over expressed in treated seedlings as against their lower expression in controls. T. hamatum treatment significantly stimulated endogenous salicylic acid (SA) levels and significantly upregulated important SA biosynthesis gene isochorismate synthase. The results indicated that T. hamatum UoM13 treatment induces resistance corresponding to significant over expression of endogenous SA, important defense enzymes, PR-proteins, and HRGPs, suggesting that SA biosynthetic pathway is involved in pearl millet for mounting systemic immunity against downy mildew pathogen.
Highlights
The sequence homology was made by using BLAST (Basic Local Alignment Search Tool) program and multiple sequence alignment was with related Trichoderma species was performed using Multalin server by using CLUSTAL 2.1 software (Fig. 1)
We showed that seed treatment with T. hamatum UoM 13 isolate reduced downy mildew severity on susceptible pearl millet cultivar under both greenhouse and field conditions
The protection offered by T. hamatum UoM 13 seed treatment was comparable to the downy mildew protection offered by the synthetic systemic acquired resistance (SAR) inducer chitosan and with that of resistant check AIMP 92901-P3
Summary
It is often cultivated under extremely harsh conditions of frequent drought, high temperature, low and erratic rainfall in infertile soils having poor water holding capacity It is currently grown in an area of over 28 million hectares worldwide, upon which approximately 500 million people depend on for their survival. Root colonization by different Trichoderma spp. like T. asperellum, T. hamatum, T. harzianum and T. virens have triggered systemic acquired resistance (SAR) against different diseases[4]. The primary objective of the present study was to evaluate if endophytic T. hamatum strain UoM 13 isolated from pearl millet host plants is efficient to elicit systemic immunity against pearl millet downy mildew disease. Since enhanced production of antimicrobial enzymes and pathogenesis-related (PR) proteins are induced by the SA signaling during induction of resistance, the present study aimed to analyze the role of endogenous SA accumulation and SA biosynthetic genes
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