Study the effects of Plant Growth Promoting Bacteria and salicylic acid in green mint (Mentha spicata L.) under drought stress conditions

In order to study the effects of Bacillus amyloliquefaciens1732 and salicylic acid on defense enzymatic and non-enzymatic mechanisms and gene expression of limonene hydroxylase using Real time PCR in green mint under drought stress, a factorial experiment based on completely randomized design wih three replications was conducted There levels of drought stress including 80% field capacity as a control, 60 and 40% of field capacity and , factor B including biological fertilizer (inoculated and non-inoculated), and factor C as salicylic acid (zero as control and 1 milli molar). The results of experiment showed that Bacillus amyloliquefaciens1732 and salicylic acid increased the non-enzymatic antioxidant traits of phenol and flavonoid. Also expression of limonene hydroxylase gene as an involving gene in monoterpenes synthesis under stress and treatment of bacteria and salicylic acid was increased. Application of bacteria and salicylic acid treatment did not have significant effect on antioxidant enzymes whereas drought stress significantly increased the antioxidant activities. The results showed that Bacillus amyloliquefaciens1732 and salicylic acid through non-enzymatic traits of total phenols and flavonoid and enhancement of second metabolites as the first defense reduced the destructive impacts of drought stress. In conclusion the plant showed better resistance and used lower energy for production of antioxidant enzymes.