Management of late leaf spot of groundnut (Arachis hypogaea) with chlorothalonil-tolerant isolates of Pseudomonas aeruginosa |
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Authors: | G Krishna Kishore ‡ S Pande A R Podile † |
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Institution: | Department of Plant Sciences, University of Hyderabad, Hyderabad 500 046;and;Pathology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, India |
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Abstract: | Fifteen groundnut-associated bacterial isolates that inhibited by > 90% the in vitro conidial germination of Phaeoisariopsis personata , causal agent of late leaf spot disease of groundnut, were applied as a prophylactic spray (108 cfu mL−1) and tested for control of the disease in the glasshouse. Two groundnut seed-associated bacterial isolates, GSE 18 and GSE 19, identified as Pseudomonas aeruginosa , reduced the lesion frequency (LF) by up to 70%. A 90-day-old peat-based formulation of P. aeruginosa GSE 18 reduced LF measured 15 days postinoculation by up to 60%. Both P. aeruginosa GSE 18 and GSE 19 were tolerant to chlorothalonil (Kavach®) up to 2000 µ g mL−1 in LB broth. In glasshouse trials, GSE 18 and GSE 19 tested in combination with reduced concentrations of chlorothalonil were highly efficient in management of the disease. The disease was completely controlled by chlorothalonil (> 250 µ g mL−1), and in the presence of GSE 18 or GSE 19, 100 µ g mL−1 chlorothalonil was equally effective. Application of rifamycin-resistant mutants of GSE 18 or GSE 19 together with chlorothalonil significantly increased the survival of these isolates in the groundnut phylloplane. In the field, a combination of GSE 18 and 500 µ g mL−1 chlorothalonil reduced disease severity comparable to 2000 µ g mL−1 chlorothalonil alone. Use of chlorothalonil-tolerant pseudomonads together with a quarter concentration of the recommended field dose of chlorothalonil doubled pod yield compared with the untreated unsprayed control. |
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Keywords: | Arachis hypogaea integrated disease management peanut Phaeoisariopsis personata |
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