Relationship between Superficial Scald Induced by 6-Methyl-5-hepten-2-one and Reactive Oxygen Species Metabolism in ‘Dangshansuli’ Pear Fruit

In this study, the relationship between 6-methyl-5-hepten-2-one (MHO) treatment and superficial scald in ‘Dangshansuli’ pear fruit and its impact on reactive oxygen species (ROS) metabolism were explored. The levels of α-farnesene, conjugated trienes, MHO, malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide anion radical and total phenols, and the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and polyphenol oxidase (PPO) in the pericarp of ‘Dangshansuli’ pear fruit treated by MHO during cold storage were measured. In addition, the development of superficial scald was observed and recorded. The results indicated that exogenous MHO could induce symptoms similar to superficial scald in ‘Dangshansuli’ pears, significantly increase the contents of MHO, H2O2 and superoxide anion radical, and decrease the activities of the antioxidant enzymes CAT, POD and SOD, and increase the contents of α-farnesene and conjugated trienes. The content of MHO in the pericarp was significantly related to the contents of H2O2 and superoxide anion radical, but was more closely correlated with the incidence rate of superficial scald than H2O2 levels. These results reveal that MHO can induce superficial scald by increasing the accumulation of ROS.