Effects Of Different Rootstock-scion Combinations On Growth,photosynthetic Characteristics And Fruit Quality Of Pear Trees

Pear is one of the important fruit trees in China,and its cultivation area and yield are among the highest in the world.At present,most of the pear orchards in China adopt the arborization cultivation method,and most of the pear varieties grow vigorously,which is not conducive to production management.Dwarf cultivation of fruit trees has the advantages of high yield,high quality and convenient mechanized operation,which is the development direction of modern fruit tree cultivation.However,there are few dwarf rootstock varieties that can be applied in pear production in China,and most rootstocks have the problem of poor regional adaptability,which seriously restricts the modernization of pear industry.In this study,the rootstock-scion combinations of 3-year-old‘Zhongai 1’and‘Qingzhen D3’and 5-year-old‘Yunnan quince’were used as test materials.The growth,branch composition,grafting affinity,photosynthetic characteristics,chlorophyll fluorescence characteristics,fruit yield and quality of different rootstock-scion combinations were measured and analyzed in order to provide reference for pear dwarfing cultivation.The main results are as follows:1.Effect of rootstock-scion combination of‘Zhongai 1’on growth and fruit of pear tree.When three-year-old varieties such as‘Korla Fragrant Pear’,‘Yuluxiang’,‘Xinli No.7’,‘Cuiguan’,‘Abate Fetel’,Youxi No.18 and‘Qiuyue’with Pyrus betulifolia+‘Zhongai No.1’,the dwarfing effect of‘Yuluxiang’was good,and the tree height was 2.15 m,which was significantly lower than that of the variety;the total branch number and short branch ratio of‘Qiuyue’were suitable;after grafting,the scion and interstock parts of all varieties were less than 1,showing a more obvious‘big foot’phenomenon;the photosynthetic performance of Youxi No.18 and‘Cuiguan’was better,the net photosynthetic rate was more than 19μmol·m^-2·s^-1,and the chlorophyll content was higher.In terms of fruit appearance quality,there was no significant difference among different rootstock-scion combinations.In terms of fruit interior quality,the flesh hardness of Youxi 18 was the lowest(5.11 kg·cm^-2),and the solid-acid ratio was the highest（158.71）.The yield per plant and yield per mu of‘Cuiguan’were 11.09 kg/plant and 1848.90 kg/667m²,respectively.The comprehensive comparison of five 3-year-old fruit varieties was carried out,and the order from high to low was Youxi 18,‘Cuiguan’,‘Qiuyue’,‘Xinli 7’,‘Korla Fragrant Pear’.2.Effect of rootstock-scion combination of‘Qingzhen D3’on growth and fruit of pear tree.When grafting the same variety on different rootstocks,that is,Pyrus calleryana+‘Qingzhen D3’grafted‘Packham’s Triumph’,‘Xianghong’,‘Qiuyang’,‘Conference’and‘Yuluxiang’3-year-old trees,compared with the tree grafted with Pyrus calleryana.The dwarfing effect of‘Conference’was better,and the dwarfing rate was 20.71%.The increase rate of total branches of‘Yuluxiang’was 56.77%.The net photosynthetic rate of‘Qiuyang’increased significantly by 6.12μmol·m^-2·s^-1.Through the comprehensive comparison of growth index,chlorophyll fluorescence characteristic index and photosynthetic characteristic index,it was found that the overall performance of dwarf‘Xianghong’,‘Qiuyang’,‘Conference’and‘Yuluxiang’was better than that of Qiaohua.There were also great differences in grafting different varieties on the same rootstock.Firstly,when 3-year-old‘Packham’s Triumph’,‘Xianghong’,‘Qiuyang’,‘Conference’and‘Yuluxiang’were grafted with Pyrus calleryana+‘Qingzhen D3’,the tree vigor of‘Conference’was weak,with a height of 2.68 m.The total branch number of‘Yuluxiang’was the highest,reaching 243.The thickness of the scion part is smaller than that of the rootstock,showing a certain‘big foot’phenomenon;the net photosynthetic rate of‘Xianghong’was 14.57μmol·m^-2·s^-1,and there was no significant difference in photosynthetic capacity between leaves.The comprehensive evaluation from high to low was‘Xianghong’,‘Yuluxiang’,‘Qiuyang’,‘Packham’s Triumph’and‘Conference’.When3-year-old‘Packham’s Triumph’,‘Xianghong’,‘Qiuyang’,‘Conference’and‘Yuluxiang’were grafted with Pyrus calleryana,the total branch number of‘Yuluxiang’was the highest,reaching 155.The photosynthetic performance of‘Packham’s Triumph’was relatively good,but the photosynthetic capacity of leaves was significantly different.The comprehensive evaluation from high to low was‘Packham’s Triumph’,‘Xianghong’,‘Qiuyang’,‘Conference’and‘Yuluxiang’.3.When grafting the same variety on different rootstocks,that is,‘Yunnan Quince’+‘Hardy’grafted‘Dangshansu’pear,‘Zaosu’,‘Yuluxiang’,‘Starkrimson’and‘Abate Fetel’5-year-old trees,compared with the tree grafted with Pyrus betulaefolia.The dwarfing rate of‘Starkrimson’was 32.56%,and the net photosynthetic rate was 6.18μmol·m^-2·s^-1 higher than that of the tree grafted with Pyrus betulaefolia.The total branch number of‘Abate Fetel’increased significantly by 56.77%compared with that of arborization.The appearance of‘Starkrimson’was significantly improved compared with that of arborization,and the flesh hardness was reduced.‘Abate Fetel’has been greatly improved in taste,and the solid-acid ratio is 1.86 times that of Qiaohua.When grafting different varieties on the same rootstock,‘Yunnan Quince’+‘Hardy’was first grafted with 5-year-old‘Dangshansu’pear,‘Zaosu’pear,‘Yuluxiang’pear,‘Starkrimson’pear and‘Abate Fetel’pear.The‘Starkrimson’tree was the shortest,only 2.32m,and the net photosynthetic rate was the highest,reaching 18.31μmol·m^-2·s^-1.The total branches of‘Abate Fetel’were as high as 243;the fruit shape index of‘Dangshansu’pear reached 1,and the appearance was excellent.‘Abate Fetel’has high solid-acid ratio,low hardness and good flavor.‘Dangshansu’pear had higher single fruit weight（326.38 g）,fruit setting rate（81.33%）and fruit number per plant（18.40）,and the highest yield per mu（1003.11 kg/667m²）and yield per plant（6.02 kg/plant）.The comprehensive scores from high to low were‘Dangshansu’pear,‘Abate Fetel’,‘Starkrimson’,‘Zaosu’,‘Yuluxiang’.When5-year-old‘Dangshansu’pear,‘Zaosu’pear,‘Yuluxiang’pear,‘Starkrimson’pear and‘Abate Fetel’pear were grafted with Pyrus betulaefolia,the net photosynthetic rate of‘Starkrimson’was the highest,reaching 12.13μmol·m^-2·s^-1.The total branch number of‘Starkrimson’was the highest（206）.The taste of‘Zaosu’was better,and the solid acid ratio was 249.60.’Red Star’has higher chromaticity and smoothness,and better appearance.The yield of‘Starkrimson’was higher;the comprehensive scores from high to low were‘Zaosu’,‘Dangshansu’,‘Abate Fetel’,‘Starkrimson’and‘Yuluxiang’.