engleski

Genetic diversity of indigenous alfalfa (Medicago sativa) rhizobia in different soil types of Istrian peninsula

Composition and characteristics of rhizobial field population are of great importance in the alfalfa production, particularly when introducing commercial inoculant strains under natural conditions. The main aim of the present investigation was to identify and to characterize the indigenous alfalfa rhizobia isolated from different field sites in the inland of Istrian peninsula. The actual composition and genetic diversity of natural field population was studied by two PCR fingerprinting methods. PCR-RFLP of 16S rDNA clearly showed that all isolates can be determined as S. meliloti. Cluster analysis of RFLP patterns obtained with RsaI, showed that none of the isolate was identical with S. medicae type strain. 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. Most of the isolates were grouped within the first major cluster while the other major cluster was formed from the same seven isolates that were characterized by slightly different PCR-RFLP profiles in comparison with all other S. meliloti strains. AFLP analysis was also performed with some S. meliloti strains of different origin. Dendrogram derived from combined AFLP profiles showed that Istrian strains were clearly separated from the other ones. Analysis of molecular variance (AMOVA) allowed relating the genetic structure of the symbiotic population to various factors, including location, soil type, vegetation and chemical properties of soil samples. Location (14.44%), pH of soil (10.85%), amount of total nitrogen in soil (9.42%) and soil type (6.91%) significantly influenced the distribution of genetic variability of the population, while the effects of vegetation and amount of potassium in soil were not found to be significant.

alfalfa; rhizobia; nitrogen fixation; PCR-RFLP; AFLP; S. meliloti

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