Biological control of downy mildew of maize caused by Peronosclerospora sorghi under environmentally controlled conditions

Downy mildew disease, caused by Peronosclerospora sorghi, is one of the most serious diseases of maize. The disease is currently managed by seed treatment with metalaxyl fungicides. However, problems regarding environmental pollution resulting from the use of fungicides and development of fungicide resistance within populations of P. sorghi are of increasing concern. Assuming that biological control by means of using antagonistic microorganisms may be an alternative for the management of this disease, the efficacy of biocontrol agents viz., Bacillus subtilis G1, Bacillus amyloliquefaciens B2, Brevibacillus brevis 57 and Pseudomonas fluorescens Pf1 for the management of downy mildew of maize and for promoting plant growth was evaluated. The results indicated that seed treatment with B. subtilis G1 and B. amyloliquefaciens B2 significantly (P = 0.05) increased the germination percentage and seedling vigour of maize as assessed by roll towel method. Among them, B. subtilis G1 was the most effective and recorded 9% and 31% increases in germination percentage and seedling vigour of maize respectively, as compared to the control. A talc- based powder formulation of B. subtilis G1 when applied through seed at the rate of 10 g/kg reduced the downy mildew incidence up to 54% under greenhouse conditions. Results of this study suggest that B. subtilis G1 is a promising bioagent for the management of downy mildew of maize and for promoting plant growth. This antagonist could be further exploited for commercial scale up for ecofriendly management of downy mildew of maize under localized climatic conditions