Inhibitory Effects And Mechanisms Of Nitric Oxide, Chitosan Oligosaccharide And Anthocyanin On Monilinia Fructicola In Postharvested Peach Fruits

Nitric oxide (NO) is an important signal molecule involved in numerous plant responsesto biotic and abiotic stress. The effects of NO solution on the pathogen and the defenseresponse of peach (Prunus persica (L.) Batsch) fruit against brown rot disease caused byMonilinia fructicolawere investigated. The results showed that15μmol L-1NO solution hadno significant inhibition on the pathogen but significantly reduced disease incidence andlesion areas in fruits. Although100μmol L-1NO solution inhibited the mycelia growth andspore germination effectively, the high concentration of NO solution (100μmol L-1) causedfruit harmness.Meanwhile,15μmol L-1NO enhanced the activities of chitinase (CHI) and β-1,3-gulucanase (GUN) in fruits. RT-PCR analysis showed that expression of four genes, CHI,GUN, pathogenesis related protein1gene (PR-1) and pathogenesis related protein10gene(PR-10) were up-regulated by NO treatment. After NO was removed by a scavenger of NO,2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), the developmentof the disease was accelerated and the defensive response disappeared. These resultssuggested that NO solution treatment protects peach fruit from pathogen infection by inducingdefensive enzymes activities and expression of PRs genes in peach fruit.Effects of chitosan oligosaccharide and anthocyanin on inhibition of Monilinia fructicolain harvested peach fruit and its possible mechanisms were studyed. After inoculated with5×105spores/mL Monilinia fructicola,‘Feicheng’ peach fruits were treated with1.5%chitosan oligosaccharide or1.5%anthocyanin, respectively. Lesion areas and diseaseincidence of fruits were investigated on day1,2,3,4,5. Activities of chitinase (CHI) and β-1,3-glucanase (GNS) and relative expression level of chitinase gene (CHI),β-1,3-glucanasegene (GNS), pathogenesis related protein1gene (PR-1) and pathogenesis related protein10gene (PR-10) at hour0,12,24,48,72after inoculated M. fructicola in peach fruit weredetermined. Lesion areas and disease incidence of fruits were inhibited effectively in chitosanoligosaccharide or anthocyanin solution treated fruit. The relative expression of PR-1、PR-10、CHI and GNS and activities of CHI and GNS in fruit were enhanced by chitosanoligosaccharide treatment. However, anthocyanin only enhanced the CHI activity and CHIrelative expression obviously. GNS activity and GNS relative expression level had notincreased. The relative expression of PR-1and PR-10were enhanced only after fruit treatedearly days. The treatment of chitosan oligosaccharide or anthocyanin showed an obvious slower decaying process of peach fruits and higher level of transcription of some diseaseresistant genes. The results indicated that chitosan oligosaccharide and anthocyanin enhancedpeach fruit disease resistance and inhibited the brown rot by affecting the pathogenesis relatedprotein (PR) and gene relative expression.In this paper, different methods on the purple sweet potato anthocyanins extractionefficiency were compared. The optimal extraction conditions were acetic acid concentrationof15%(V/V), extraction temperature of40°C, extraction time of60min, solid-to-liquid ratioof1:25(gmL-1). Under the optimized extraction conditions, the experimental yield ofanthocyanins was up to1.03mgg-1.The superoxide anion radical scavenging ability ofanthocyanin was worse than ascorbic acid at lower concentration (<0.7mg mL-1)，but betterat higher concentration (>0.7mgmL-1). The hydroxyl radical scavenging ability ofanthocyanin was far greater than that of ascorbic acid，and was close to100%at theconcentration of0.5mgmL-1. The preliminary determination by spread plate method showedthat anthocyanin inhibited the growth of E. coli significantly.