Evaluation of the effect of Azospirillum spp. inoculation, alone and in combination with phosphate solubilizing bacteria Bacillus megaterium , on alleviation of the effects of salinity stress on Mung bean (Vigna radiata L.)

Increasing salinity of soil and water is the most important concern for agriculture in dry lands. In this research the effect of Azospirillum inoculation alone and in co-inoculation with phosphate solubilizing bacteria was investigated in alleviating the adverse effect of salinity on mung bean Vigna radiata L. cv Gohar) for 2-year under field condition. The study was a factorial experiment based on a randomized complete block design with three replicates. The main factors were application of various serovars of Azospirillum, phosphate solubilizing bacteria Bacillus megaterium, co-inoculation of both bacteria, non-inoculated treatment as control and two levels of salinity irrigation (0.2 and 12 dS m-1). Analysis of variance indicated significant effect of salinity and microbial inoculation on mung bean seed yield. Salinity resulted in reduction of seed yield by 88%. Under salinity and non-salinity conditions, the highest amount of grain yield, seed weight, and seed number was observed in plants with seeds inoculated with Azospirillum. The minimum Na and K and maximum P contents of seeds were observed in Azospirillum inoculated plants. Co-inoculation with Azospirillum and Bacillus megaterium resulted in no further beneficial effect under saline and non-saline conditions. Overall, Azospirillum appeared to be effective in mitigation of the adverse effect of NaCl and its co-inoculation with phosphate solubilizing bacteria gained no more additives benefit.