Resistance To Gray Mold Of Different Varieties Of Apple Cultivar And Effects Of UV-C Treatments On Control Of Botrytis In Postharvest Apples

The object of this work was to investigate resistance difference to gray mold between six mid-late maturity varieties(‘Qinguan’, ‘Ralls’, ‘Red Fiji’, ‘Huangjinshuai’, ‘Jonagold’ and ‘Empire’), and resistance mechanism from physiological and biochemical change and organization structure of apple fruits. The effects and mechanism of UV-C treatments on control of botrytis in postharvest apples was also investigated.1. The infection rate and the diameter of the spot differed significantly between six mid-late maturity varieties after inoculations with Botrytis cinerea Pers. In the screening test for multiple disease resistance, ‘Qinguan’ and ‘Ralls’ performed as comprehensive high resistant Followed by ‘Red Fiji’ and ‘Huangjinshuai’ while ‘Jonagold’ and ‘Empire’ were high susceptible.2. The activity of chitinase(CHT), β-1,3-glucanase(GLU) and peroxidase(POD) of ‘Qinguan’ and ‘Ralls’ varieties rose rapidly after inoculation and kept high level in the late disease. However, The activity of CHT and GLU of ‘Jonagold’ and ‘Empire’ kept low level in the whole observation period. The activity of oxidase(PPO) of ‘Ralls’, ‘Red Fiji’ and ‘Huangjinshuai’ sised in a longer time than other varieties, and kept high level In the late inoculation.3. There were significant differences in fruit structure between different varieties. The skin thickness and layer of skin cells and disease resistance were positively correlated. There was no correlation between thickness of cuticle, epidermal cells close to the skin, pulp cells and resistance to gray mold of apple fruits.4. 3.5 kJ/m2 and 7.0 kJ/m2 UV-C treatments significantly decreased the incidence of gray mold rot, and effectively suppressed the expansion of lesions caused by B.cinerea, and the suppression effect of 7.0 kJ/m2 UV-C treatment on gray mold was better than 3.5 kJ/m2 UV-C treatments. However, 10.5 kJ/m2 UV-C treatment had an adverse effect on gray mold of apple fruits only after inoculation for the earlier days while at the later stage after inoculation 10.5 kJ/m2 UV-C treatment could even increase morbidity of fruits and promote the expansion of lesions.5.The activity of chitinase(CHT), β-1,3-glucanase(GLU), peroxidase(POD), polyphenol oxidase(PPO) and phenylalanine ammonia enzyme(PAL) of apple fruits can be promoted remarkably by 3.5 kJ/m2 and 7.0 kJ/m2 UV-C treatments, and phenolics content were also increased significantly. The promotion effect of 10.5 kJ/m2 UV-C treatment on those defense enzymes activities and phenolics content was found only in the fist several days after inoculation.