Effect of Pesticides on Plant Growth Promoting Traits of Greengram-Symbiont, Bradyrhizobium sp. strain MRM6

The aim of this study was to investigate the toxicity of herbicides (metribuzin and glyphosate), insecticides (imidacloprid and thiamethoxam) and fungicides (hexaconazole, metalaxyl and kitazin) at the recommended and the higher dose rates on plant growth promoting activities of Bradyrhizobium sp. under in vitro conditions. The Bradyrhizobium sp. strain MRM6 was isolated from nodules of greengram plants. Pesticide-concentration dependent progressive-decline was observed in plant growth promoting traits of the strain MRM6 apart from exo-polysaccharides which increased consistently on increasing pesticide concentrations. Generally, the highest toxicity to plant growth promoting characteristics of the Bradyrhizobium sp. strain MRM6 was observed when the strain MRM6 was grown with three times the recommended field rates of glyphosate, imidacloprid and hexaconazole.