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چکیده
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-------Salinity toxicity is a worldwide agricultural and eco-environmental problem. The intent of this study was to determine the salt tolerance of Piriformospora indica and strains of Azospirillum, isolated from nonsaline and saline soil, as well as to determine their affect on the tolerance of wheat to soil salinity. In this study, an experiment was conducted to investigate the salt stress tolerance abilities of the endophytic fungi, P. indica, and Azospirillum strains, isolated from non-saline and saline soil, at five NaCl levels (0, 0.1, 0.2, 0.3, 0.4, 0.5 mol L1). Additionally, a greenhouse experiment was conducted to test the effects of these selected microorganisms under increasing salinity levels on seedling growth, solute accumulation (proline and sugars), and photosynthetic pigments (Chl a, b, ab) of seedling wheat. Azospirillum strains were isolated in Iran from the root of field-grown maize from non-saline soil with an EC ¼ 0.7 dS m1 and from saline soil with an EC ¼ 4.7 dS m1. Plants were irrigated with non-saline wateretap water with an electrical conductivity water (ECw) value of 0.2 dS m1, as well as low, moderate and severe saline water-irrigation with saline water with an ECw of 4 dS m1, 8 dS m1 and 12 dS m1, respectively. The upper threshold of P. indica salinity tolerance was 0.4 mol L1 NaCl in both liquid and solid broth medium. The upper thresholds of the salt adapted and non-adapted Azospirillum strains were 0.2 and 0.4 mol L1 NaCl, respectively. The results indicated a positive influence of the organisms on salinity tolerance, more with the saline-adapted Azospirillum strains than the non-adapted strains. P. indica was more effective than the Azospirillum strains. These results could be related to a better water status, higher photosynthetic pigment contents and proline accumulation in wheat seedlings inoculated with P. indica. The benefits of both isolates and P. indica depended on two factors: water salinity and
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