Induced systemic resistance protects pearl millet plants against downy mildew disease due to Sclerospora graminicola

Abstract

Three-day-old seedlings of pearl millet (Pennisetum glaucum), when root-dip inoculated with different concentrations of zoospores of Sclerospora graminicola, had increasing degrees of downy mildew disease incidence with increasing inoculum load. Inoculation of plants with 6000 zoospores ml⁻¹ caused infection in all plants but resulted in only 18% disease as evidenced by external symptom manifestation. The plants treated to this suboptimal level of zoospores, when challenged after 4-6 days with 40 000 zoospores ml⁻¹ remained predominantly healthy compared with the controls, suggesting induction of resistance by the suboptimal dose of inoculum used. The resistance induced was systemic and protected tillers and inflorescences.