Effect of Piriformospora indica and Azotobacter chroococcum on mitigation of zinc deficiency stress in wheat (Triticum aestivum L.)

Zinc deficiency is a global nutritional problem in agricultural soils in large number of countries, causing decreased crop yields and grain nutritional quality. This study was conducted to investigate the effect of individual and co-inoculation of two plant-growth-promoting microorganisms (PGPMs); Azotobacter chroococcum and Piriformospora indica; on some physiological traits such as uptake of mineral nutrients, antioxidant enzyme activities, photosynthetic pigments, lipid peroxidation in leaves of wheat plants under Zn deficiency conditions. Bacterial treatment either alone or in combination with P. indica, significantly increased shoot and root biomass compared to non-inoculated controls under Zn deficiency conditions. Highest levels of Zn and P and also chlorophyll (a & b) and carotenoid concentrations were recorded in P. indica- inoculated plants both under Zn-sufficient and - deficient conditions. Individual and co-inoculation of A. chroococcum with P. indica caused a significant decrease in Fe and P concentrations in shoot compared with the control treatment. MDA (Malondialdehyde) content of inoculated plants with all microbial treatments was lower than in leaves of corresponding non-inoculated plants under Zn-deficiency conditions. Ascorbate peroxidase and peroxidase activity of inoculated plants with A. chroococcum and A. chroococcum + P. indica were higher than the other treatments under Zn-deficient conditions. Also, activity of peroxidase enzyme was induced in endophyte-inoculated plants, while ascorbate peroxidase activity was declined in such conditions. Generally, the studied microbial treatments, particularly A. chroococcum, can be proposed as a useful tool for alleviating Zn deficiency stress in sensitive plants to zinc deficiency.