Effects of Alternaria alternata Infection on Reactive Oxygen Species Metabolism in Pericarp of Jiashi Muskmelon
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Abstract:
Jiashi melon was chose as experimental material. Non-invasive inoculation methods of melon with Alternaria alternata was used. The objective of this study was aimed to compare the resistance difference of no-netted, small-netted and large-netted pericarp to pathogenic bacteria during storage. The relationship between reactive oxygen species (ROS) metabolism and key enzymes activity was investigated. The results showed that, when Jiashi melon was infected by Alternaria for 30 days, the incidence of disease rates of non-netted group, small-netted group and large-netted group were 77.77%, 84.17%, 88.02%, espectively. The superoxide radical (O2·-) production rate and Glutathione (GSH) content of each experimental group increased firstly and then decreased. The content of hydrogen peroxide (H2O2) increased firstly, then decreased, and increased during storage. The content of Malondialdehyde (MDA) of exocarp increased firstly and then decreased. However, the content of MDA of endocarp increased continuously. The O2·- production rate, GSH, H2O2 and MDA content of exocarp were higher than that of endocarp during the infection period. The activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione reductase (GR) of each experimental group increased firstly and then decreased. Themaximum of SOD activity in no-netted, small-netted and large-netted of exocarp were 49.19 U, 39.29 U and 31.81 U, respectively, and that of endocarp were 32.36 U, 24.28 U and 19.30 U, respectively. The maximum of CAT activity in no-netted, small-netted and large-netted of exocarp were 485.95 U, 393.68 U and 220.40 U, respectively, and that of endocarp were 202.67 U, 228.30 U and 137.93 U, respectively. The maximum of POD activity in no-netted, small-netted and large-netted of exocarp were 28.62 U, 24.84 U and 23.13 U, respectively, and that of endocarp were 14.46 U, 9.73 U and 8.58 U, respectively. The maximum of GR activity in no-netted, small-netted and large-netted of exocarp were 378.32 U, 170.24 U and 196.15 U, respectively, and that of endocarp were 70.58 U. 45.61 U and 66.67 U, respectively. Ascorbate peroxidase (APX) activity increased continuously during storage. APX activity of exocarp was higher than that of endocarp. APX activity of no-netted group was higher than that of small-netted group and large-netted group. In conclusion, the postharvest disease resistance of Jiashi melon pericarp was closely related to the metabolism of ROS. The disease resistance of exocarp was stronger than that of endocarp. The disease resistance in no-netted group was stronger than that of small-netted group and large-netted group.
