engleski

Stress tolerance assays and genetic diversity of Sinorhizobium meliloti field population

The studying of rhizobial biodiversity opens up the possibility to preserve and maybe to exploit some indigenous strains with hidden symbiotic or ecological potential. In order to improve the beneficial effect of alfalfa inoculation it is important to characterize the indigenous strains and to obtain information about actual composition of rhizobial field population. The main aim of the present study was to characterize indigenous rhizobia associated with alfalfa (Medicago sativa L.) in different regions of Croatia. Over 250 isolates were obtained from root nodules of alfalfa. To study their diversity and characterize them in relation to environmental conditions of their soils of origin, a polyphasic approach was used. Stress tolerance assays revealed significant variations in pH tolerance while almost all isolates showed similar tolerance to elevated salt concentrations and growth temperatures. PCR-RFLP of 16S rDNA revealed most of isolates to be closely related to S. meliloti. However, several isolates produced slightly different RFLP pattern from S. meliloti type strain and other isolates. Dendrogram derived from AFLP profiles revealed considerable genetic diversity among S. meliloti isolates. Only a few strains were identical or nearly identical to each other. The strains originated from the same region were mostly grouped within the same cluster. Better understanding of rhizobial ecology and selection of locally adapted and genetically defined strains as well as their targeted application is one among many approaches to improve the nitrogen fixation efficiency and crop productivity.

nitrogen fixation; rhizobia; Sinorhizobium meliloti; indigenous strains; stress tolerance; genetic diversity

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