Hot water dipping induced resistance to disease Colletotrichum musae on banana fruits and its effect on related enzymes

The influences of hot water dipping treatment on fruit softening, degreening, size of lesion, activities of several relevant defense enzymes in postharvest banana fruit were investigated. Softening and degreening are not evident for the fruits treated with 52℃ hot water dipping(HWD) for 10 min, and stored at 25℃ for 12 days, while the control fruit softens and degreens obviously under the same condition. Inoculating fruit with spore suspension of Colletotrichum musae softening and degreening process of the control fruit is accelerated and its size of lesion expands quickly, whereas HWD treated fruit presents slower softening, degreening and lesion expansion. Compared with the control, in the peel of HWD treated fruit, the activities of Polyphenol Oxidase(PPO), Peroxidase(POD) and Superoxide Dismutase(SOD) decrease, the activity of Phenylalanine Ammonialyase(PAL) displays no difference, while the activity of Lipoxygenase(LOX) increases dramatically. The above results indicate that HWD treatment delays fruit ripening and induces disease resistance of banana fruit. The relationship between the increased disease resistance and the activities of the relevant enzyme was discussed.