پراکنش گونه‌های سینوریزوبیومی Sinorhizobium meliloti و S. medicae همزیست با یونجه در مناطق غربی ایران

To characterize the geographical distribution of medicago-nodulating rhizobia in western regions of Iran, 950 Sinorhizobium isolates were trapped from a combination of two local alfalfa populations (Hamedani, Nikshahri) together with a foreign cultivar ( Kodi) and soil samples from eight sites across Kurdestan, Kermanshah, Eastern Azarbayjan and Lorestan provinces. Also, a total of 45 isolates were obtained from nodules of naturally grown Melilotus officinalis (14 isolates) and Trigonella foenum-graecum (31 isolates) plants in Isfahan. On the basis of PCR partial amplification of the plasmid born nod box gene and chromosomal mucR gene of the isolates,16S ribosomal DNA PCR-restriction fragment length polymorphism analysis, and the nucleotide sequence, three isolates from alfalfa, seven isolates from M. officinalis and 13 isolates from T. foenum-graecum were proved to be Sinorhizobium medicae. The remaining isolates (943 from alfalfa, seven from M. officinalis and 18 from T. foenum-graecum) were identified as S. melilloti. Both species, S. meliloti and S. medicae, were recovered from nodules of all the hosts although S. meloti was clearly more dominant in nodulating different populations of alfalfa. Taken together, these results indicated that the abundance of S. meliloti is independent of the site of isolation and have a wide geographical distribution. In this study, the banding pattern resulting from PCR amplification of 16S rRNA gene, followed by digestion with Rsa I, clearly differentiated S. meliloti and S. medica strains, showing that PCR-RFLP is an appropriate method to discriminate medicago-nodulating rhizobian with relative rapidity.