Diversity of root nodule bacteria from leguminous crops

Abstract

In the present study, a total of 353 nodule-associated bacteria were isolated from 220 legume plant samples belonging to Cicer arietinum (85), Glycine max (74), Vigna radiata (21) and Cajanus cajan (40). A total of 224 bacteria were identified as fast-growing Rhizobium spp. on the basis of differential staining (Gram staining and carbol fuchsin staining) and biochemical tests. All the isolates were tested for indole acetic acid production (IAA), phosphate solubilization and siderophore production on plate assay. To examine the effect of volatile organic metabolites (VOM) and water soluble soil components (WSSC) on nodule bacteria, culture conditions were optimized by observing the effects of various parameters such as pH, salt content and temperatures on the growth of bacteria. Selected rhizobia were subjected to random amplified polymorphic DNA (RAPD) and amplified ribosomal DNA restriction analysis (ARDRA) analysis to identify their species. On the basis of RAPD and ARDRA, 10 isolates were identified as Rhizobium meliloti. In this study, Rhizobium GO4, G16, G20, G77, S43, S81, M07, M37, A15 and A55 were observed as the best candidates among the tested bacteria and can be further used as potent bioinoculants.