Characterization of rhizobia from legumes of agronomic interest grown insemi-arid areas of Central Spain relates genetic differences to soil properties.

摘要

A study of symbiotic bacteria from traditional agricultural legumes from Central Spain was performed to create a collection of rhizobia from soils differing inphysicochemical, analytical and/or agroecological properties which could bewell-adapted to the environmental conditions of this region, and be used forsustainable agricultural practices. Thirty-six isolates were obtained fromroot-nodules of fifteen legume species (including Cicer arietinum, Lathyrussativus, Lens culinaris, Lupinus spp., Medicago sativa, Phaseolus vulgaris, Pisumsativum, and Vicia spp.) from three agriculture areas with soils of different pHsand from a forest area with undisturbed soils. Phenotypical characterizationrevealed uniformity across the thirty-six isolates, with important exceptions in terms of environmental tolerance (three isolates survived at high temperatures,three at high salinity and three at acid pH). The molecular analysis of 16S rRNA gene showed a close relationship of twenty-nine isolates to Rhizobiumleguminosarum, one to Rhizobium gallicum, one to Mesorhizobium ciceri, two toSinorhizobium (Ensifer) meliloti and three to Bradyrhizobium canariense. Thesequence analysis of a symbiosis-specific gene, nod C, showed a correlation with the plant host and grouped twenty-six isolates with Rhizobium leguminosarum bv.viciae, establishing the diversity in relation to legume-host. The 16S-23S rRNAintergenic spacer (IGS) region allowed for intraspecific differentiation, so thatstrains with equal 16S rRNA were grouped by means of their soil origin. Theseresults indicated that phenotypical and genetically related strains may be widelydistributed in this region and that soil abiotic characteristics could have asubstantial bearing on the selection of the strains living in each environment.