engleski

Identification and symbiotic characterization of indigenous rhizobia nodulating common bean in Croatia

Common bean (Phaseolus vulgaris L.) is very valuable grain legume in human diet and its consumption can contribute to health improvement. Common bean production in Croatia is limited to small-scale farmers and generally neglected despite favourable environmental conditions. It is assumed that indigenous rhizobial strains with hidden potential for efficient nitrogen fixation are present in Croatian soils. The main aim of the present study was to determine genetic diversity and symbiotic efficiency of indigenous common bean rhizobia isolated from different field sites in the Northwestern Croatia. Identification of isolates was initially performed by MALDI-TOF MS. RAPD fingerprinting was used to assess rhizobial genetic diversity and to select representative strains for phylogenetic analysis, which included those of rrs, recA, atpD and nodC genes. The results obtained with MALDI-TOF MS methodology show that the strains from this study matched with different species from the Rhizobium leguminosarum phylogenetic group with score values higher than 2.0. The analysis of the core genes rrs, recA and atpD showed that most of strains isolated from common bean nodules in Croatia belong to the species R. leguminosarum and R. hidalgonense, a species recently described in America (1). Two strains were identified as R. pisi and several strains formed lineages phylogenetically divergent from all species currenlty encompassed in the Rhizobium leguminosarum phylogenetic group. The results of the nodC gene analysis showed that all indigenous common bean rhizobia from Croatian soils belong to symbiovar phaseoli. This is the first report about the existence of this symbiovar within the species R. pisi, which already contains strains from symbiovars viciae and trifolii (2). Symbiotic efficiency of selected indigenous strains and their compatibility with two common bean cultivars were tested in greenhouse experiment. Most efficient strains were those belonging to R.leguminosarum species. Further investigation is needed in order to select the most suitable strains for application as biofertilizer for sustainable common bean production in Croatia.

Common bean, rhizobia, MALDI-TOF MS, rrs, recA, atpD, nodC

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