Distribution of Melanin Producing Sinorhizobia Isolates in West and North-West of Iran

To characterize the distribution of melanin producing Medicago-nodulating rhizobia in western and north-western of Iran, 982 Sinorhizobium isolates were trapped from a combination of three alfalfa populations (Hamedani, Nikshahri, Kodi) and soil samples from eight sites across Kurdestan, Kermanshah, Eastern Azarbayjan and Lorestan provinces. All rhizobial isolates were examined for their ability to produce melanin (Mel+). According to the results, 24.1% of them were Mel+, as well as the reference strain S. meliloti GR4. Analysis of melanin production revealed more melanin producing isolates among different sites in comparison of different cultivars. Therefore, it can be concluded that the influence of field soil type in dominance of melanin producing strains is more than the host cultivars. The presence of 456 bp amplified fragment using primers designed from the mepA gene in 30 strains of rhizobial strains and its absence in 20 other strains was in accordance with the results of melanin production in the medium, showing that all strains producing melanin contained mepA gene. Multiple sequence alignment revealed that the sequence of mepA gene in S. meliloti is conserved, while this sequence in S. medicae had limited changes.