Efficacy of Bacillus subtilis G-1 in suppression of stem rot caused by Sclerotium rolfsii and growth promotion of groundnut

A total of seven biocontrol agents with known antifungal activity against other soilborne fungal pathogens were screened for their antagonistic potential against Sclerotium rolfsii Sacc, the causal agent of stem rot disease of groundnut (Arachis hypogaea L.) by dual culture assay. Among the various biocontrol agents tested Bacillus subtilis strain G-1 was the most effective in inhibiting the mycelial growth of S. rolfsii and recorded an inhibition of 28%. Groundnut seeds when treated with B. subtilis G-1 showed significant increases in root length, shoot length and seedling vigour. A talc-based powder formulation of the highly effective strain, B. subtilis G-1, was developed and its efficacy in controlling groundnut stem rot was determined under greenhouse conditions. The results indicated that seed treatment with the powder formulation of B. subtilis G-1 alone effectively reduced the incidence of stem rot and increased the pod yield; but combined application through seed and soil increased the efficacy. Seed treatment and soil application with B. subtilis G-1 reduced the stem rot incidence from 80 per cent (with non-bacterized seeds) to 5 per cent. When the treated seeds were sown in soil, the antagonist moved to the rhizosphere and multiplied well in it. These results suggest that B. subtilis G-1 is an effective bioagent against stem rot of groundnut. Further studies are required to assess its efficacy in controlling stem rot of groundnut under field conditions.

Bacillus subtilis strain G-1 has good potential as a microbial agent for biological control of stem rot of groundnut caused by Sclerotium rolfsii.