عنوان مقاله [English]
A large area of Iraninan soils have different levels of salinity; so that crop production, the crop production in these stress conditions is very limited. Azotobacter can stimulate plant growth by various mechanisms. Inoculation of plants with superior native isolates of Azotobacter that are compatible with saline areas may enhance plant growth under salinity stress. In this study, 20 isolates of Azotobacter native to soils of Iran were evaluated in terms of ability to phosphate solubility, potassium releasing, auxin and siderophore production. Salinity tolerance of isolates was investigated in bacterial culture medium and electrical conductivity of them at 10, 20, 30, 40 and 50 dS.m-1.
Six selected isolates at three levels of salinity were evaluated on maize Single Cross 704 in a factorial completely randomized block design with three replications in a greenhouse experiment. Salinity stress was applied through irrigation with water with electrical conductivity of 0.36 (normal water), three and six dS.m-1. The laboratory results revealed that Az63, Az69 and Az70 were the most effective isolates in terms of phosphate solubilisation and potassium releasing and, siderophore production. All isolates grew well in electrical conductivity of 10 and more isolates at 20 dS.m-1. Az22 and Az66 isolates were salinity tolerant up to dS.m-1. The greenhouse results showed that inoculation with Az69 in the condition of irrigation with normal water increased dry weight of clusters 64 percent compared to the control. Inoculation had no significant effect on growth indices in at irrigation with water with electrical conductivity of 3 and 6 dS.m-1. In this study, Az69 isolate was selected for further studies.