Isolation and Evaluation of Rhizospheric Bacteria for Biological Control of Chickpea Wilt Pathogens

Three hundred rhizospheric isolates of bacteria collected from different regions of Karnataka were screened for in vitro antagonism in dual culture on Tryptic Soya Agar (TSA) against five fungal pathogens viz. , Botrytis cinerea , Macrophomina phaseolina , Sclerotium rolfsii , Rhizoctonia solani and Fusarium oxysporum f. sp. ciceris . Four isolates selected as potential antagonists were identified as Pseudomonas putida (PDBCAB 19), P. fluorescens (PDBCAB 2), P. fluorescens (PDBCAB 29) and P . fluorescens (PD BCAB 30) and their root colonizing ability was tested. The total rhizosphere population was the highest (log cfu 6.4) for P . fluorescens (PDBCAB 29) after four days of germination. The rhizosphere population stabilized (log cfu 4.0 to 5.0) after eight days of germination. Three pathogens namely F. oxysporum f. sp. ciceris (wilt pathogen), R . solani and M.phaseolina (root rot pathogens) were targeted by the four selected antagonists under greenhouse conditions. The maximum plant stand (100%) was observed with P.jluorescens (PDBCAB 29 and 30) treated pots for R. solani and M. phaseolina . P. putida (PDBCAB 19) and P . fluorescens (PDBCAB 30) were able to fully control F. oxysporum f. sp. ciceris . All the four antagonists promoted growth of chickpea. P . fluorescens isolates (PDBCAB 29 and 30) produced the maximum growth. Survival of P . fluorescens (PDBCAB 29) in a talc based formulation was monitored over a period of 90 days at room temperature.