Inhibition on brown rot disease and induction of defence response in harvested peach fruit by nitric oxide solution

Nitric oxide (NO) is an important signal molecule involved in numerous plant responses to biotic and abiotic stresses. The effect of nitric oxide (NO) solution on pathogen infection and defence response of peach (Prunus persica (L.) Batsch) fruit against brown rot disease caused by Monilinia fructicola was investigated. The results showed that 15 mu mol l(-1) NO solution did not significantly inhibit spore germination, germ tube length or pathogenicity of M. fructicola, but significantly reduced disease incidence and lesion areas in the fruit. Although 100 mu mol l(-1) NO solution effectively inhibited the spore germination, germ tube elongation and pathogenicity of M. fructicola, the high concentration of NO solution caused damage to the fruit. Moreover, 15 mu mol l(-1) NO enhanced the activities of chitinase (CHI) and beta-1,3-glucanase (GNS) in the fruit. RT-PCR analysis showed that the expression of four genes, CHI, GNS, pathogenesis-related protein 1 and 10 genes (PR-1, PR-10) all increased after NO treatment. Conversely, pretreatment with 100 mu mol l(-1) NO scavenger, 2-4-carboxyphenyl-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), rendered the fruit relatively susceptible to pathogen infection and inhibited the defence response of the fruit. These results suggest that NO solution treatment can protect peach fruit from pathogen infection by inducing the activities of the defence enzymes and the expression of PR genes.