engleski

Biodiversity of indigenous rhizobia isolated from soils in Zadar County

Symbiotic relationship between nodule bacteria Sinorhizobium meliloti and alfalfa (Medicago sativa L.) allows use of inert atmospheric nitrogen which has a great significance in sustainable agricultural production. The inoculation of legume seeds with highly effective strains of rhizobia is recommended in order to increase the utilization of symbiotic nitrogen fixation. The main aim of this investigation was to isolate indigenous strains of S. meliloti from soils of Zadar region and their identification using molecular methods in order to determine the genetic variability within natural populations of these soil bacteria. Also, the main of this paper is to assess the possibility for growth of indigenous alfalfa rhizobia in conditions that are beyond the optimal values for their growth. The study included 20 isolates, references strains of Sinorhizobium medicae LMG 18864 and S. meliloti 2011 and type strain S. meliloti 30135. Identification of the isolates was performed using three molecular methods based on PCR amplification: 16S rDNA PCR - RFLP, RAPD - PCR and ERIC – PCR.. Growth of the strains was analyzed at different pH values, temperatures, salt and heavy metals concentrations and carbon source. The results of 16sS rDNA PCR-RFLP method showed that 17 isolates could be regarded as S.meliloti species and that three isolates were significantly different from both reference strains.The results of this study showed that rhizobial strains tolerate alkaline conditions, while their growth was inhibited in acidic conditions. They also growth at temperature of 37°C which is higher than their optimal growth temperature (26-30°C). Such indigenous strains tolerate a certain amount of salt and particular heavy metals, and can use other source of carbon besides commonly used mannitol.

symbiotic nitrogen fixation ; indigenous Sinorhizobium meliloti strains ; phenotypic strain characterization ; genetic diversity ; 16S rDNA PCR – RFLP ; RAPD – PCR ; ERIC – PCR

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