Seed priming with plant gum biopolymers enhances efficacy of metalaxyl 35 SD against pearl millet downy mildew

Abstract

‘Priming’ the plant and seed induces a physiological state in which plants are able to activate defense responses. Plant-based exudates are excellent gum biopolymers which contain plant growth-regulating hormones with priming potential without any side effects. In this study, gum exudates of Acacia arabica, Moringa oleifera, Carica papaya and Azadirachta indica were evaluated for synergistic effects of seed priming with exuded gum biopolymer combined with metalaxyl (Apron 35 SD) on pearl millet seed quality, growth parameters, and resistance to Sclerospora graminicola. Seeds of 7042S were primed with gum biopolymers and metalaxyl 35 SD and evaluated under laboratory and greenhouse conditions. Seed germination and vigor were synergistically enhanced using gum biopolymers solution (1:2 w/v) with 3 g kg−1 metalaxyl 35 SD. A. arabica and A. indica gum biopolymers alone or with 3 g kg−1 of metalaxyl 35 SD resulted in seed germination of >91%. Seed priming with 6 g kg−1 of metalaxyl 35 SD gave 89% seed germination and was not significantly different from control. A similar trend in vigor was observed among treatments. Seed priming with gum biopolymers alone provided varied disease protection levels when compared with the control. A. arabica or A. indica gum with 3 g kg−1 of metalaxyl 35 SD was the superior treatment, offering significant 86% disease reduction while exhibiting a growth-promoting effect. Synergistic use of gum biopolymers and metalaxyl 35 SD by seed priming is highly effective in growth promotion and management of pearl millet downy mildew disease.