Effects of Alternaria alternata infection on antimicrobial substances and activities of enzymes related to reactive oxygen metabolism in Muskmelon

Take Jiashi Melon as the experimental materials, this study was aimed to study the resistance difference of pericarp and sarcocarp to pathogenic bacteria during storage.muskmelon was inoculated with A.alternata at different depths were 3 mm ( pericarp) , 5 mm ( pericarp and sarcocarp at the junction) and 10 mm ( sarcocarp) , and stored at 7 ℃ cold storage.Regular inspection of the Lesion diameter of pericarp and sarcocarp, the contents of total phenols and flavonoids in antibacterial substances, and the activities of polyphenol oxidase ( PPO) , peroxidase ( POD) , superoxide dismutase ( SOD) and catalase ( CAT) activity.The results revealed that pericarp lesion diameter was significantly smaller than the sarcocarp ( p < 0.05) during the storage.The disease resistance of pericarp is greater than sarcocarp. The contents of antibacterial substances and reactive oxygen metabolism related enzymes in the 3, 5 and 10 mm inoculated groups were significantly higher than those in the control group ( p < 0.05) , the fruit of 3 mm inoculation group had higher resistance to disease, pericarp and sarcocarp cooperate to resist the infection of Alternaria alternata, pericarp exerts a greater resistance to disease.