ارزيابي مقاومت به شوري و خشكي جدايه هاي بومي Sinorhizobium meliloti استان كرمان

The study of salt and drought tolerance of Sinorhizobium meliloti isolated from Kerman province

Salinity and drought stress can significantly affect plant growth in arid and semi-arid regions. Legume - rhizobium symbiotic relationships can also be influenced by these limiting factors. It is well known that the host plant inoculation by native strains with high efficiency has a positive effect on plant yield and biological nitrogen fixation process. The main aim of this investigation was to evaluate the salinity and drought tolerance of 49 isolates of Sinorhizobium meliloti collected from Kerman province in southern Iran. Salinity and drought tolerance of all isolates were examined in liquid TY media containing 0, 100, 200, 300, 400, 500, 600 and 650 mM NaCl and 0, 203, 298, 373, 438, 496, 548 and 573 g/L of Polyethylene glycol (PEG-6000), respectively. This experiment was carried out using a factorial arrangement in completely randomized design whith three replicants. The results showed that salinity and drought tolerance among isolates was significantly different. All isolates were grouped in three clusters: sensitive, semi-sensitive and tolerant based on their growth rate in TY media containing different concentrations of NaCl and PEG-6000. The results also showed that all tolerant isolates excreted more exopolysacharides compared to the sensitive and semi-sensitive ones. Based on salinity and drought experiments, two isolates of Sinorhizobium meliloti i.e.S27K and S36K were selected as superior in this expriment.