Development of broad-spectrum actinomycetes for biocontrol and plant growth promotion of food crops.

Current investigation is aimed at identifying actinomycetes and their metabolites with multiple actions against insect pests and pathogens, including plant growth promotion (PGP). We characterized 137 actinomycetes, isolated from 25 different herbal vermi-composts, for their antagonistic potential against charcoal rot in sorghum (caused by Macrophomina phaseolina) and wilt in chickpea (caused by Fusarium oxysporum f. sp. ciceri [FOC], respectively) by dual culture assay. Of the isolates, three most promising M. phaseolina antagonistic strains (CAI-21, CAI-26 and MMA-32) and five most promising FOC antagonistic strains (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were further evaluated for their antagonistic and PGP potential by blotter paper assay, greenhouse and field conditions. All the eight strains were characterized for their physiological traits (tolerance to salinity, temperature, pH and compatibility to antibiotics and fungicides) and further evaluated in the field for their PGP on rice. Ten strains (CAI-8, CAI-13, CAI-70, CAI-85, CAI-87, CAI-132, CAI-133, CAI-155, SAI-25 and BCA-508) were also found effective in suppressing Helicoverpa, Spodoptera and Chilo spp. under laboratory and greenhouse conditions. The sequences of 16S rDNA gene of all eighteen strains matched with Streptomyces, but species appeared to be different. This study confirms that the selected Streptomyces strains have broad-spectrum biocontrol and PGP properties.