Streptomyces spp., a potential biocontrol agent of charcoal rot of sorghum caused by Macrophomina phaseolina

Seven strains of Streptomyces spp. (BCA-546, BCA-659, BCA-667, BCA-689, BCA-698, CAI-8 and CAI-133; demonstrated previously to have potential for plant growth-promotion on sorghum and chickpea) were evaluated for their antagonistic potential against Macrophomina phaseolina, causal agent of charcoal rot disease of sorghum, by dual culture assay, secondary metabolite production assay and in greenhouse disease screen. All the seven strains inhibited M. phaseolina in both dual culture as well as secondary metabolite production assays but four of them (BCA-546, BCA-667, BCA-698 and CAI-8) were notable. When these selected four strains were tested for their antifungal activity in greenhouse on sorghum by tooth pick method, BCA-546 and CAI-8 significantly reduced the disease. The stem samples of the control and Streptomyces sp. treated plants were analysed under scanning electron microscope, where the xylem and phloem tissues of the Streptomyces spp. treated plants were found intact compared to that of infected control plants. This study indicates that the selected two Streptomyces strains, BCA-546 and CAI-8, have the potential to control charcoal rot disease in sorghum