Preliminary Study Of Storage And Disease Resistance To Peronophythora Litchii Of Main Species Of Litchi Fruits In Fujian

This paper has studied the differences of fruit storage and disease resistance to Peronophythora litchii of 4 litchi cultivars including Guiwei,Lanzhu,Wuye and Yuanhong. Based on observation under skimming electric microscope, the relationship between pericarp ultrastructure with storage and disease resistance was also discussed.The result showed that there were significant differences of browning index and rate of healthy fruit among the different litchi cultivars during storage. The brown index of Lanzhu and Guiwei cultivars achieved the maximum after storing for 6 days, which was ahead of the Wuye and Yuanhong cultivars for 4 days. The ratio of good fruit was nearly zero after storing for 4 days, while the ratios of good fruit of Wuye and Yuanhong were 61.9% and 82.1% separately. The results of biochemical mechanism of storage property showed that the rates of superoxide anion radicals, membrane permeability, CAT, GSH and PPO had different variation tendencies.Wuye and Yuanhong cultivars had a lower membrane permeability than Lanzhu and Guiwei. After storing for 108 hours, the pericarps of Yuanhong and Wuye had 24.76% and 23.80% lower membrane permeability separately than that of Lanzhu. The catalase activities of Yuanhong and Wuye were about 733.60% and 509.70% separately higher than that of Lanzhu. The cellulase activities of Yuanhong and Wuye were about 16.61% and 9.25% lower than that of Lanzhu. The GSH content of Yuanhong and Wuye were about 65.83% and 34.71% higher than that of lanzhu. The PPO activity of Yuanhong and Wuye increased about 48.28% and 46.19%, while Guiwei and Lanzhu reduced about 15.66% and 60.77%. After storing for 36 hours, the rates of superoxide anion generation of Wuye and Lanzhu had a oxidative burst, but Lanzhu was about 55.66% higher than Wuye.Study result also showed that there were significant differences of disease resistance to P. litchii among the different litchi cultivars. In 4 days after inoculation with P. litchii, the fruit disease index and incidence rates of Lanzhu and Yuanhong were 71.6%, 94.9% and 100%, 98.3% respectively, while that of Wuye and Guiwei were only 13%, 17.9% and 41.5%, 58.5% respectively. After inloculation with P. litchii, the membrane permeability, polyphenol oxidase, peroxidase, catalase, cellulase, PAL activity, superoxide anion generation rate, MDA content of tested cultivars were different. such as after inoculated for 108h, the membrane permeabilities of Wuye, Guiwei and Yuanhong were lower 23.23%, 14.46% and 10.19% than that of Lanzhu separately. If after inoculted for 84 h,Wuye and Guiwei had 35.26% and 32.63% higher polyphenol oxidase activities separately than Yuanhong. If after inoculated for 60 h, the hydrogen peroxide activity of Wuye and Guiwei were 76.02% and 30.32% higher respectively than that of Yuanhong. If after inoculated for 12- 60 h , the ascorbic acid contents of Wuye and Guiwei were higher than that of Lanzhu and Yuanhong.After comparatively observing the ultrastructure of litchi pericarp by SEM , it was showed that all litchi pericarps of tested cultivars were composed of many peaks and valleys, but their ranges were different, such as Wuye neatly arranged in close.There were also many microcracks on surface of litchi pericarps. The microcrack of Wuye was smaller than that of other tested cultivars, which had a relationships with storage and disease resistance of litchi fruits.