Inoculation effect of endophytic fungus Piriformospora indica and bacteria Azotobacter chroococcum on activity of antioxidant enzymes and wheat tolerance to zinc deficiency (Niknejad cultivar) in greenhouse conditions

Zinc (Zn) deficiency is one of the most widespread micronutrients deficiencies in plants that causes severe reduction in their growth and yield. An increase in reactive oxygen species (ROS) levels and a decrease in efficiency of detoxification mechanisms may be the major reasons for impairment of various cellular functions in Zn-deficient plants. This study was conducted in order to investigate the effects of individual and simultaneous inoculation of endophytic fungus, Piriformospora indica, and plant growth-promoting rhizobacterium, Azotobacter chroococcum, on biochemical properties, antioxidant enzyme activities and growth of wheat plant (Niknejad cultivar) in Zn deficiency and sufficiency conditions. The experiment was conducted in greenhouse of the Soilless Culture Center of Isfahan University of Technology by using the sterile sand-perlite (2:1 v/v) medium, as factorial in a completely randomized design with three replications. The results showed that Zn deficiency decreased shoot dry weight, carotenoid's content, total amount of Zn in shoot and antioxidant enzyme activities in control treatment (plants were not inoculated with fungi and bacteria). Inoculation of individual and simultaneous of P. indica and A. chroococcum resulted in increase of shoot dry weight at Zn deficiency condition. However, the highest shoot dry weight belonged to individual inoculation of A. chroococcum. Inoculated plants with P. indica had the highest total amount of Zn in shoot and concentration of carotenoids at both levels of Zn. Whereas, individual inoculation of A. chroococcum and also in combination with P. indica had only significant effect on increasing the total amount of Zn in shoot at Zn deficiency condition. Inoculation of A. chroococcum alone and also in combination with P. indica resulted in inducing antioxidant enzyme activities of ascorbate peroxidase and peroxidase in response to Zn deficiency. Whereas, individual inoculation of P. indica resulted in increasing and decreasing the activities of peroxidase and ascorbate peroxidase, respectively. In general, inoculation of wheat plant (Niknejad cultivar) with the studied microorganisms in this research, particularly inoculation of A. chroococcum, can serve as a useful method for alleviating deleterious effects of Zn deficiency stress.