Variation in plant growth promoting activities of Azospirillum under pesticide stress

AbstractThe study was conducted to assess the effect of pesticides chlorpyriphos 50% EC, imidacloprid 30.5% SC, carbendazim 50% WP, mancozeb 75% WP, butachlor 50% EC and thiobencarb 50% EC on survival ability and plant growth promoting activities of Azospirillum. Based on results of compatibility test, Azospirillum survived the recommended doses of imidacloprid 30.5% SC, carbendazim 50% WP and mancozeb 75% WP but failed in presence of chlorpyriphos 50% EC, butachlor 50% EC and thiobencarb 50% EC. Also, Azospirillum showed highest tolerance to imidacloprid 30.5% SC (5.4 mg L-1) and lowest to carbendazim 50% WP (0.11 mg L-1). Among the various plant growth promoting activities assessed, highest indole acetic acid (IAA) production (30.85 µg mL-1), ammonia excretion (4.35 µg mL-1) and Phosphate (P) solubilization (10.79 µg mL-1) was recorded in the presence of recommended doses of imidacloprid 30.5% SC followed by carbendazim 50% WP and mancozeb 75% WP. However, lower auxin production, ammonia excretion and P-solubilization was reported in the presence of half - minimum inhibitory concentration (½MIC) doses of chlorpyriphos 50% EC. Remarkable quantity of siderophore production was noted in the recommended doses of imidacloprid 30.5% SC followed by mancozeb 75% WP and carbendazim 50% WP. This study is the first report on variation in functional traits of nitrogen fixing bacterium, Azospirillum, under herbicide, fungicide and insecticide stress.