The involvement and the relationship between nitric oxide (NO) and hydrogen peroxide (H2O2) in methyl jasmonate (MeJA)-induced immune responses in blueberries against Botrytis cinerea was explored using diphenylene iodonium (DPI, NADPH oxidase inhibitor) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger). MeJA induced NO and H2O2 burst and enhanced the resistance of blueberries by elevating defense-related enzymes and the phenylpropanoid pathway. However, the above impacts stimulated by MeJA were weakened by DPI and destroyed by cPTIO. Furthermore, cPTIO abolished the increment in H2O2 by regulating the activities of NADPH oxidase, superoxide dismutase, catalase, and ascorbate peroxidase, whereas DPI weakened the increase in H2O2 but barely affected the generation of NO and the activity of nitric oxide synthase elevated by MeJA. These results indicated that NO and H2O2 were involved in the MeJA-induced resistance in blueberries, and NO worked upstream of H2O2 in this process.
Keywords: blueberry; disease resistance; hydrogen peroxide; methyl jasmonate; nitric oxide.