Induction of resistance in pearl millet against downy mildew disease caused by Sclerospora graminicola using benzothiadiazole, calcium chloride and hydrogen peroxide- a comparative evaluation

Abstract

A major constraint in the production of pearl millet is its vulnerability to downy mildew disease caused by Sclerospora graminicola. Induction of resistance in pearl millet against downy mildew disease was studied treating seeds of the highly susceptible cultivars of pearl millet using the plant activator benzothiadiazole (BTH) (CGA 245704), calcium chloride (CaCl₂) and hydrogen peroxide (H₂O₂). 0.75% BTH, 90 mM CaCl₂ and 1.0 mM H₂O₂ were efficient in managing the disease by giving 78%, 66% and 59% protection, respectively, against downy mildew disease. In vivo quantification of Sclerospora graminicola by an enzyme-linked immunosorbent assay confirmed reduced fungal biomass in plants induced for resistance. Optimization of the time gap between the inducer treatment and inoculation with the downy mildew pathogen identified a gap of 4 days for building up of maximum resistance. Inducer treatment not only offered protection but also increased the vegetative and reproductive growth parameters and enhanced grain yield. Among the inducers used, BTH gave more protection than calcium chloride and hydrogen peroxide. Plants raised from H₂O₂ treatment enhanced the vegetative and reproductive growth parameters compared to the other two inducers. Seedlings raised from inducer-treated seeds recorded an early and increased hypersensitive response as a reaction to Sclerospora graminicola inoculation.