Evaluation of a Microbial Consortium for Growth Promotion and Suppression of Sclerotial Rot of Groundnut

Sclerotial rot caused by Sclerotium rolfsii is a soil-borne disease of groundnut and is difficult to manage because of the persistent nature of the pathogen in soil. This study investigated a compatible microbial consortium comprising Rhizobium sp. R5, potassium-mobilising bacteria (KMB) isolate K1, Bacillus megaterium and Pseudomonas fluorescens for improving groundnut growth and reducing sclerotial rot. The four selected bacterial isolates showed no visible inhibition zone in the compatibility test and were combined in equal proportions (1:1:1:1). Their effect on seed germination and seedling growth was first evaluated by the rolled paper towel method and subsequently under pot conditions using groundnut cv. TAG-73. The consortium recorded 97.00% germination, 9.10 cm root length, 9.83 cm shoot length and a seedling vigour index of 1836.21 under rolled paper towel conditions. In pot culture, the consortium recorded 90.00% germination, 9.93 cm root length, 14.16 cm shoot length and the highest seedling vigour index of 2168.10. An incidence of sclerotial rot of 22.41% was recorded following consortium application compared with 57.93% in the untreated control, corresponding to 61.31% disease reduction relative to the control. The results indicate that the compatible four-member microbial consortium has the potential to improve early plant growth and suppress S. rolfsii under pot conditions.