| Pear is one of the most important cultural fruit trees. And pear fruit as the main fruit daily consumed has the traditional advantage in Chinese fruit imports and exports.With the improvement of fruit quality demand in domestic and foreign market, it was necessary to perfect technique of producing high quality pear. Sand pear is the main cultural pear variety, increasing for its requirement in market, and its yielding acreage in China's south area account for 37.35% of China's pear total acreage. But it is widely existed in sand pear's production in south area that fruit appearance quality is not excellent. Bagging is a vital solution to improve sand pear's quality. Consequently, this experiment studied the effect of bagging to improve fruit quality of sand pear and the countermeasure using Pyrus pyrifolia Nakai Eli 2 as material by means of different paper bag types, treatments and in different periods. The results were as follows:1.Bagging could significantly improve the appearance of fruits with smaller and less fruit dots, decreasing rusty stain. But it had different effect by different types of bags, two -layer bags were better than one-layer bags. The size and density of the fruit dots and index of rusty stain from four treatments of twice bagging of small wax bags and two-layer bags from Taiguo, South korea, Xiaolin, and one-layer white bag from Taiguo were 0.20mm,0.20mm,0.23mm,0.29mm,15.3units/cm~2,13.9units/cm~2,13.9units/cm~2,18.3units/c m~2 and 4.07,2.59,4.26,1.67, and the control was 0.98mm, 24.1 units/cm~2 and 15.65. Twice bagging had the best effect and was significantly different compared to the controls.2.Bagging increased the peel thickness ,which was only related to the types of paper. The pulp firmness from four trentments,which were of twice bagging of small wax bags, two-layer bags from South korea,Taiguo,Xiaolin,and one layer white bag from Taiguo were 10.3kg/cm~2,10.0 kg/cm~2,9.8 kg/cm~2,10.1 kg/cm~2,and they were all significantly different with other treatments. The pulp firmness of the yellow single bag from Taiguo treatment was 5.9 kg/cm and it was the lowest. The pulp firmness from all treatments in bagging directly was significant different, but it was unsignificantly different between the treatments and control. Fruit shape index of all treatments were unsignificantly different.3.The size of sand pear would decreased through bagging,but the average weight of per fruit of all treatments were unsignificantly different It was obviously linear between transparency of bags(x) and the size of fruits(y) with a positive correlation coefficient of 0.80 , the regression coefficients of 0.99 and the regression equation was Y=159.61+0.99X.4.The fruit colour and luster changed significantly through bagging. Correlation between fruit colour and luster and the transparency of bags(x) was noticed in this study. Regression equation and correlation coefficients are:brightness (L), Yl=74.45-0.71x, R=-0.84; colority coordinate value (A), Y_A=-16.68-0.77x, R = -0.86; colority coordinate value (B), Y_b=52.52+1.86x,R =0.91. The three regression relationship and the regression coefficients above were significant by marked test.5.The content of soluble solid, soluble sugar and titratable acid in fruits would decrease through bagging. The content of TSS, SS and TA from three treatments of one layer bags including yellow , white one-layer bags from Taiguo, and one-layer paper bags decreased less than that of treatments of two layers bags, while four types of twice bagging decreesed...
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