Abstract This research was consisting of two pot and one field experiments. The first pot experiment studied the effects of inoculation with two mycorrhizal fungi (Funneliformis mosseae and Rhizophagus intraradices) and Azotobacter on the bread (Roshan and Bahar) and durum (Behrang and Yavarus) wheat cultivars grown in a soil naturally contaminated to heavy metals under three salinity levels (0, 75 and 150 mM NaCl). In this study salinity decreased biomass, K/Na and P content, while increased Cd, Pb and Zn contents in wheat plants. Durum cultivars were more salt sensitive than bread cultivars and this was more evident at low salinity levels. The concentrations of Cd, Pb and Zn in the grains were greater in durum cultivars. The mycorrhizal-associated increase in plant biomass was maximum at high level of salinity. The beneficial effects of F. mosseae under none-saline and low salinity condition were greater than those of Rh. intraradices. Azotobacter inoculation only increased the growth of salt tolerant cultivars and its positive effects were greatest at low salinity. Wheat inoculation by mycorrhizal fungi along with cultivation of low heavy metal-accumulating varieties can be applied as an effective strategy for mitigating the impacts of soil salinity and heavy metals. The second pot experiment was conducted to eva‎luate the effects of inoculation with the two mycorrhizal species (F. mosseae and Rh. intraradices) and Azotobacter on the growth and physiological characteristics of the salt tolerant (Roshan) and salt sensitive (Bahar) wheat cultivars under three salinity levels aforementioned in the first experiment. Salinity significantly decreased shoot and root biomass of both cultivars, but to a smaller extent in Roshan. The reductions in the biomass production were accompanied with decreases in N, P and K contents and increases in proline and MDA and antioxidant enzyme activities. The salt tolerant cultivar showed less decreases in nutrient content and higher increases in proline and antioxidant enzyme activities. Peroxidase enzyme showed a higher contribution in salt tolerance induction as compared to catalase and ascorbate peroxidase. Mycorrhizal inoculation improved plant growth by increasing nutrient content, antioxidant enzyme activity and decreasing lipid peroxidation. The positive effects of inoculation were in most cases greater in the plants inoculated by F. mosseae. The superiority of this species was associated with lower increases in MDA and H2O2 accompanied by greater increases in root area and volume, shoot N, P and K/Na and antioxidant enzyme activities. Higher benefits from mycorrhizal inoculation were taken as the level of salinity was increased. Salt tolerant cultivar was more positively responsive to mycorrhizal inoculation under none-saline treatment, but the sensitive cultivar was more affected by inoculation under saline conditions. The results from this experiment showed that mycorrhizal inoculation could promote the growth and salt tolerance of wheat cultivars by improving osmoregulation, antioxidant enzyme activity and reducing lipid peroxidation. The field experiment was performed using the same cultivars and mycorrhizal and salinity treatments. Salinity had adverse effects on grain number per plant and grain yield which caused by the reduction in RWC and MSI, impaired nutrient balance and increased H2O2 production and lipid peroxidation. However, inoculation with mycorrhiza led to increased adaptation to salinity and improved wheat productivity through higher RWC and MSI, better osmotic regulation by accumulation of proline, increased nitrogen and potassium uptake, decreased sodium uptake as well as reduced H2O2 content and lipid peroxidation. The results of this experiment showed that salinity-caused osmotic, ionic and oxidative damages to plants could be effectively modified by mycorrhizal inoculation and the extent of the positive effects was cultivar and mycorrhizal species dependent.

مرتضي زاهدي

حسين شريعتمداري، پرويز احسان زاده

حميدرضا اصغري، فرشيد نوربخش، حميدرضا عشقي زاده