Bacteriocin-producing native rhizobia of green gram (Vigna radiata) havingcompetitive advantage in nodule occupancy

Bradyrhizobium and Rhizobium strains nodulating green gram (Vigna radiata) were screened for bacteriocin production. Nine out of 280 native isolates s howed growth inhibition of 5 or more homologous strains out of the 20 sensi tive strains tested. The growth inhibition was found due to the production of high molecular weight bacteriocin(s) in Rhizobium strains VRF10 and VRF5 7. The antagonistic activity of the inhibitory substance was retained after treatment with trypsin, lysozyme, RNase and DNase as well as heat. Under m ixed growth conditions in broth culture, bacteriocin-producing strain VRF10 suppressed the growth of sensitive strain VRF76. Co-inoculation of the two strains VRF10 and VRF76 on green gram showed that the bacteriocin-producer strain VRF10 occupied significantly more number of nodules than the sensit ive strain VRF76, suggesting the role of bacteriocin production in nodulati on competitiveness.