Field application of Bacillus subtilis isolates for controlling late blight disease of potato caused by Phytophthora infestans

Abstract

Abstract Field studies on the biocontrol activity of four B. subtilis isolates viz., B. subtilis MTCC-2422 (T-3), B. subtilis KU936344 (T-4), B. subtilis KU936345(T-5) and B. subtilis KU936341 (T-6), against late blight disease of potato caused by fungus like-organism Phytophthora infestans were investigated. These isolates produce mycotoxins against the causal organism. The fungicide (Mancozeb) M 45 (CURZATE®) was used as positive control. Potato (Solanum tuberosum) cultivar, Kufri Jyoti was used. The treatments were utilized as soil drenching as well as foliar spray. Results reveal that, bacterial treatments significantly reduced disease incidence of late blight compared with the control. Bacterial treatments increased the plant vegetative parameters like plant height, sprouting, number of leaves, fresh weight and dry weight of plants. In addition, treatments also showed the clear difference between commercial and non-commercial tuber yield/hectare. In this experiment, two observations displayed the reduction of the disease severity. There was 32.73% increase in the control plot and 14.3% in chemical fungicide, while in bacterial treatments there was 12.75%, 14.09%, 4.7% and 4.13% increase in the T3, T4, T5 and T6, respectively. Soil drenching of bacterial culture gave the high yield in commercial potato tubers, even when compared with the chemical fungicide. The total yield of control block was 166.04 quintals/hectare but non-commercial yield was 101.07 quintals/hectare. In chemical fungicide, total yield was 188.8 quintals/hectare and non-commercial tubers was 69.66 quintals. The bacterial treatments T4, T5, T6, showed less non-commercial potato yield 48.29, 22.60 and 24.67 quintals/hectare in the total yield of 177.02, 212.89 and 190.737 quintals/hectare in respective treatments. So this study uncovers that B. subtilis treatments are effective under field condition for the control of potato late blight.