MEDICA GO SATIVA تاثير تنش شوري بركارآيي تثبيت بيولوژيكي ازت در يونجه

Effect of salinity stress on efficiency of biological nitrogen fixation in alfalfa (Medicago sativa)

In order to examine salinity tolerance and efficiency of biological nitrogen fixation (BNF) of Sinorhizobium meliloti, isolates of the bacteria were sampled from several saline regions of Iran. Then isolates were subjected to salinity treatments of 0,1,2 and 3% sodium chloride using a solution culture medium. After 5 days, the growth of the bacteria were measured and evaluated, and the bacteria were classified from sensitive to tolerante. In experiment 2 sensitive to tolerante bacteria, and alfalfa cultrivars, Ranger and Gharayunjeh, were treated using Johnson nutrient solution (without nitrogen) in Leonard method with salinity treatment of 0, 0.1, 0.3 and 0.5% sodium chloride to evaluate the efficiency illʹ BNF in the isolates. Results showed that nodule numbers in 0.1% soduim chloride were higher than control. However, in higher concentrations of sodium chloride (>0.1%) the number of nodules decreased with increasing the salinity. Also, root and shoot decreased with salinities higher than 0.1%. The greatest nitrogen content of root and shoot were obtained with isolates 18 and 14 and the lowest ones were observed in isolates Iii and 22. Results showed that there is no good correlation between EC of the bacteria inhabitant and the salinity tolerance of the bacteria.