Search for Agrochemical and Heavy Metal Tolerant Strains of Pseudomonas fluorescens and Rhizobium

Fifty Pseudomonas fluorescens (Pf) and 28 Rhizobium strains were isolated from rhizospheric soil and root nodules of pigeonpea, biochemically characterized and tested for their tolerance to fungicides, insecticides and heavy metals under in vitro conditions. Among fungicides tested, only carbendazim showed compatibility to all P. fluorescens strains, and Rhizobium strains were tolerant to all the fungicides and insecticides. Lead nitrate was compatible with all P. fluorescens and Rhizobium strains. Maximum number (37) of Pf strains was sensitive to cobalt chloride hexahydrate and nickel chloride, while Rhizobium strains (26) were highly sensitive. Hence, well characterized agrochemical and heavy metal compatible P. fluorescens and Rhizobium strains can be combined with biocontrol agents as a seed treatment or soil application for the management of soil or seed borne diseases.