A Study On Sugar Metabolism In Fruit And Technology For Improving Fruit Quality In ’Cuiyu’ Pear

Most south areas of the Yangtze River in China are rich in heat, and the temperature rise rapidly in early spring, which are suitable for developing precocious sand pears.’Cuiguan’ pear (Pyrus pyrifolia Nakai cv.’Cuiguan’) was spreaded rapidly throughout Zhejiang province these years since breeding. As simplified cultivar structures and centralized maturity periods, there were some problems coming out these years, such as lower fruit prices, weakened market competitiveness, poor planting efficiency.One of new cultivars ’Cuiyu’ pear was selected on the basis of ’Cuiguan’ pear, and more precocious than ’Cuiguan’ pear.’Cuiyu’ pear was used as one of materials in this study to compare the differences on fruit quality and sugar metabolism enzymes during growth period with ’Cuiguan’ pear and ’Chuxialu’. Effects of bagging and reflective films (RF) on fruit quality were also studied in ’Cuiyu’ pear to provide a scientific basis and technical guidance on promotion and application. The main results were as follows:1.’Cuiyu’ pear,’Cuiguan’ pear and ’Chuxialu’ pear were used as materials in this study to compare the differences on fruit quality and sugar metabolism enzymes during growth period. The results showed that total soluble solids and soluble sugars of ’Cuiyu’ and ’Chuxialu’ were lower than ’Cuiguan’ pear. Delaying harvest can improve the sucrose content of the fruit and thus increase the total sugar content of fruits and fruit sweetness of ’Cuiyu’ pear.’Cuiyu’ pear and ’Chuxialu’ pear could be harvested at110d-115d after full bloom, and that of ’Cuiguan’ pear at115d-120d. Because the appearance quality and fruit weight of ’Cuiyu’ and ’Chuxialu’ were better than ’Cuiguan’, the former ones are more suitable to be promoted and cultivated in south areas of the Yangtze River.2. Three kinds of bags, NK-15,1-KK, and1-LP, were used in ’Cuiyu’ pear under open field and shed frame cultivation, to study bagging effects on fruit quality and sugar metabolism enzymes during growth period, using fruits without bags as controls. It was found that the colour of the fruit was significantly affected when treated with1-LP bags. The contents of TSS, fructose, sorbital, sucrose were lower in three kinds of bags than that of control, expecially sucrose. The activities of sugar metabolism enzymes were obviously affected by bagging. The activities of acid invertase (AI) and sucrose cleavage direction (SSc) was higher than that of control, thus the activities of sucrose synthase direction (SSs) and sucrose phosphate synthase (SPS) were lower than that of control. Bagging also reduced the fruit weight, and increased the hardness of fruit, expecially1-LP bags. Comparing with the three bags, the contents of fructose and sucrose which have great contribution to the sweetness in NK-15and1-LP were higher than those in1-KK, and there was more fruit russet in1-LP than NK-15. Considering of bag cultivation, NK-15was better than1-KK and1-LP.3. The effects of covering orchard floors with silvery reflective film (RF) in open field and shed frame cultivation on fruit quality of ’Cuiyu’ pear were studied two months after full bloom. The results showed that the fruit weight, hardness, TSS, soluble sugars were little affected by RF in open field and shed frame cultivation with good light condition, but the appearance quality was greatly improved by RF.