| Summary: | Background: This study was done to investigate the impact of drought stress, inorganic and organic Fe sources on biodegradation of crude oil in the Cd polluted soil under cultivation of canola inoculated with Piriformospora indica.Methods: Treatments consist of soil application of pure iron from Fe sources ((Fe sulfate and Fe chelate) (0, 60 and 90 kg Fe pure/ha)), and canola plant inoculated with P. indica cultivated in the Cd (0, 15 and 20 mg Cd/kg soil)-polluted soil that was naturally polluted with crude oil under drought stress. After 70 days, the plants were harvested and the soil and shoot Cd concentration was determined using atomic absorption spectroscopy (AAS). In addition, the biodegradation of crude oil was measured.Results: Using 90 kg/ha pure iron from iron chelate significantly improved the biodegradation of crude oil in the soil by 13.1 and 8.9% under normal soul moisture and drought stress, respectively. Plant inoculation with P. indica had significant effect on increasing the biodegradation of crude oil in the soil by 12.1%. Furthermore, the soil microbial respiration was also increased. The ascorbate peroxidase (APX) and peroxidase (POX) enzyme activity was significantly increased under heavy metal toxicity.Conclusion: Using organic and inorganic Fe sources has significant effects in increasing the biodegradation of crude oil in the soil under normal soil moisture regime and drought stress. Regardless of soil moisture regime, plant inoculation with P. indica had significant effects on reducing the Cd concentration of the plant and increasing the biodegradation of crude oil in the soil, respectively.
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