Characterization of Rhizobium spp. bean isolates from South-West Spain

Rhizobium spp Strains able to nodulate beans (Phaseolus vulgaris L.) were isolated from Andalusian (Southern Spain) soils with no record of recent bean cultivation (except soil 14) and no known history of bean inoculation in this area. The isolation methodology was devised to obtain an heterogeneous rhizobia population from each soil sample, by using three different bean cultivars as trap-host. No association was found between the presence of rhizobia nodulating bean and the chemical or textural properties of the soils. The isolates were grouped on the basis of their symbiotic effectiveness on bean cv. Canellini under greenhouse conditions, intrinsic antibiotic resistance (IAR), lipopolysaccharide (LPS) and protein profiles, melanin production, and by amplified rDNA restriction analysis (ARDRA). Most of the isolates were more effective than the reference strains Rhizobium leguminosarum by. phaseoli TAL1121, R. etli type strain CFN42 and R. tropici type strain CIAT899. The symbiotic effectiveness of the isolates could not be related with other traits analyzed. Predominantly, a two bands-LPS profile was found amongst the isolates. Most of them have been assigned to R. etli by ARDRA and seem to be more competitive than R. gallicum or R. giardinii isolates. Additionally, a strong interaction between the bean cultivar and the native rhizobia populations was observed. (C) 2000 Elsevier Science Ltd. All rights reserved.