ABSTRACT
Downy mildew of pearl millet caused by the biotrophic oomycete Sclerospora graminicola is the most devastating disease which impairs pearl millet production causing huge yield and monetary losses. Chitosan nanoparticles (CNP) were synthesized from low molecular weight chitosan having higher degree of acetylation was evaluated for their efficacy against downy mildew disease of pearl millet caused by Sclerospora graminicola. Laboratory studies showed that CNP seed treatment significantly enhanced pearl millet seed germination percentage and seedling vigor compared to the control. Seed treatment with CNP induced systemic and durable resistance and showed significant downy mildew protection under greenhouse conditions in comparison to the untreated control. Seed treatment with CNP showed changes in gene expression profiles wherein expression of genes of phenylalanine ammonia lyase, peroxidase, polyphenoloxidase, catalase and superoxide dismutase were highly upregulated. CNP treatment resulted in earlier and higher expression of the pathogenesis related proteins PR1 and PR5. Downy mildew protective effect offered by CNP was found to be modulated by nitric oxide and treatment with CNP along with NO inhibitors cPTIO completely abolished the gene expression of defense enzymes and PR proteins. Further, comparative analysis of CNP with Chitosan revealed that the very small dosage of CNP performed at par with recommended dose of Chitosan for downy mildew management.
Subject(s)
Chitosan/pharmacology , Disease Resistance/genetics , Nanoparticles/chemistry , Nitric Oxide/biosynthesis , Pennisetum/drug effects , Plant Proteins/genetics , Acetylation , Benzoates/pharmacology , Catalase/antagonists & inhibitors , Catalase/genetics , Catalase/immunology , Catechol Oxidase/antagonists & inhibitors , Catechol Oxidase/genetics , Catechol Oxidase/immunology , Chitosan/chemistry , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/immunology , Germination/physiology , Imidazoles/pharmacology , Nitric Oxide/agonists , Nitric Oxide/antagonists & inhibitors , Pennisetum/genetics , Pennisetum/immunology , Pennisetum/microbiology , Peronospora/growth & development , Peronospora/pathogenicity , Peroxidase/antagonists & inhibitors , Peroxidase/genetics , Peroxidase/immunology , Phenylalanine Ammonia-Lyase/antagonists & inhibitors , Phenylalanine Ammonia-Lyase/genetics , Phenylalanine Ammonia-Lyase/immunology , Plant Diseases/genetics , Plant Diseases/immunology , Plant Diseases/microbiology , Plant Proteins/antagonists & inhibitors , Plant Proteins/immunology , Seedlings/drug effects , Seedlings/genetics , Seedlings/immunology , Seedlings/microbiology , Seeds/drug effects , Seeds/genetics , Seeds/immunology , Seeds/microbiology , Superoxide Dismutase/antagonists & inhibitors , Superoxide Dismutase/genetics , Superoxide Dismutase/immunologyABSTRACT
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.
