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Biodiversity and Biogeography of Sinorhizobium meliloti strains trapped by alfalfa in different Croatian regions

The studying of rhizobial biodiversity opens up the possibility to preserve and maybe to exploit some indigenous strains with hidden symbiotic or ecological potential, particularly under unfavourable conditions. 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. Recently, the assessment of diversity within indigenous Sinohizobium meliloti field population has received increased attention in Croatia. In this study, the soil samples for rhizobial isolation were collected from three different regions in Croatia (Istrian peninsula, North-West Croatia and Central Croatia), Figure 1. Greenhouse pot experiment was established in order to obtain nodules for isolation procedure. Due to better description of field sites, main physical and chemical characteristics were determined in all soil samples.. A total of approximately 130 strains were isolated by trapping with Medicago sativa from soils in the three different regions: to analyse the genetic diversity and population structure of Croatian strains. To study their diversity and characterize them in relation to environmental conditions of their soils of origin, a polyphasic approach was used. All the isolates were typed by AFLP of genomic DNA and their phenotypic diversity was analysed by tolerance to high salt concentration, different pH levels and high temperatures. Moreover, the soil of the different sampling locations within each region was characterized by chemical-physical analysis and by the present vegetation. AFLP data were statistically analysed in connection with environmental factors such as geographic origin and soil characteristics as well as the tolerance levels associated with strain phenotype

symbiotic nitrogen fixation; indigenous Sinorhizobium meliloti strains; genetic diversity; phenotypic strain characterization

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