Plant growth-promotion by Streptomyces spp. in sorghum (Sorghum bicolor L.)
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Seven strains of Streptomyces spp.: BCA-546 (KF770898), BCA-659 (KF770889), BCA-667 (KF770888), BCA-689 (KF770899), BCA-698 (KF770900), CAI-133 (KF770895) and CAI-8 (KF770890), reported earlier to produce biocontrol and plant growth-promoting (PGP) substances were further evaluated for PGP traits in sorghum under greenhouse and field conditions. Under greenhouse conditions, plant height, leaf area and weight, root length and weight, shoot weight, panicle weight and seed weight were enhanced in plots inoculated with Streptomyces spp. than the un-inoculated control at 30, 60 days after sowing (DAS) and at final harvest. Similarly, treatment with Streptomyces spp. led to growth and yield enhancements under field conditions at 60 DAS and final harvest. Among the seven strains, BCA-698, BCA-689, BCA-546 and BCA-659 were found to be superior for PGP. Under field conditions, at both flowering and harvest stages, the soil organic C, available P and total N were also found to improve with Streptomyces spp. treatments. A scanning electron microscopic study showed extensive root colonization of sorghum. The gene expression profiles revealed up-regulation of β-1,3-glucanase, indole acetic acid (IAA) and siderophore genes. Based on the present findings, the seven selected Streptomyces strains could be employed to enhance plant growth and yield in sorghum.