Effect of genistein on symbiosis of common bean and Rhizobium leguminosarumb.v.phaseoli in salinity stress

Genistein is an important isoflavonoide in bean root exudates. It is as a molecular signal in the symbiosis to induce nod genes of Rizobium, exudation of nod factor with bacteri and finally making physiological responses in root and formation of nitrogen fixator nodule. Salt stress cause a disturbance in exudation of this compounds by plant root. The objective of this study was investigating the effect of Rhizobium leguminosarumb.v.phaseolipre-induced with genistein (G) on nodulation, nitrogen fixation and growth of the common bean in salinity stress. The experiment was planned in three levels of genistein (G0=0, G5=5, G20=20 µM) and irrigation with three levels of salinity (S0=0, S1=2, S2=4 ds/m) and were combined in a factorial fashion in complete randomized design with three replicates in agriculture college greenhouse of Ferdowsi University. Plants were harvested after 30 days and wet and dry weight of root and shoot, number and weight of root nodule and plant nitrogen were measured. The results showed that weight and number of nodule were more sensitive to salinity rather than dry weight of plant. Genistein application with 5 and 20 µM concentration increased number, weight of nodule and bean nitrogen uptake in non saline soil. Adding 20 μM genistein increased average weight of each nodule in S1 level of salinity. Nodules number and weight decreased with increasing salinity from S1 to S2. Despite decreasing nodulation, by increasing salinity, plant nitrogen uptake and concentration was not decreased by using genistein.