Effects of different dwarfing rootstocks on growth, yield and quality of Liaoyan apple trees

【Objective】High yield, good quality, quick income and economical use of land are the advantages of high dense planting. Liaoyan apples are famous for high quality, good appearance and strong resistance to diseases. The effects of different dwarfing rootstocks on tree growth, photosynthetic characteristics, yield and quality of this variety were studied in this paperin order to provide scientific basis for selecting suitable rootstock-scion combinations to promote the further development of varieties.【Methods】The experiment was carried out in 2021 and 2022 at Liaoning Institute of Pomology. Liaoyan apple scions were grafted on different dwarfing rootstocks (B9, GM256, M9-T337, Liaozhen No. 2) in the spring of 2018. The healthy nursery trees were selected. for planting in the spring of 2019, eighty trees were planted for each combination. There were 20 trees of each combination in a row. The spacing was 1.0 m × 4.0 m. The differences of the tree body development, number of branches and proportion, photosynthetic characteristics, fruit yield and quality were compared in 2021 and 2022.SPSS17.0 software was used for statistical analysis of the data. The data obtained were processed using 2007 Microsoft Excel (Microsoft, Redmond, USA) software.【Results】The survival rate, tree height, coverage rate, crown diameter, ratio of variety to rootstock, length of main branches, number of main branches and total number of branches of the Liaoyan trees grafted on B9 were the lowest, while the proportion of the medium and short branches of the Liaoyan trees on B9, GM256, M9-T337 and Liaozhen No. 2 was the highest. The trees onB9 had the highest net photosynthetic rate and SPAD value, while the trees on GM256 had the lowest transpiration rate and the highest water utilization rate. The single annual yield, cumulative yield and high-quality fruit rate of the trees on GM256 were the highest, the fruit color difference L value and a value of the trees on B9 were the highest, and the fruit color difference b value of the trees on GM256 was the highest. Fruit shape index was not different among the trees on different rootstocks. The trees on B9 had the lowest fruit production. The trees on GM256 had the highest hardness, brittleness, soluble solid content and solid acid ratio of the fruits. The survival rate of Liaoyan apple trees with different rootstocks was GM256＞Liaozhen No. 2＞M9- T337＞B9. The trees on B9 had the lowest coverage and crown diameter. The trees on M9-T337 had the largest diameter, and the ratio of the scion and rootstock diameter of the trees on B9 was the smallest, and that on GM256 was the largest. The field performance showed that B9 had the strongest dwarfing effect, resulting in too weak tree growth potential. The photosynthetic characteristics of the Liaoyan apple tree were affected by different rootstocks, and the chlorophyll content SPAD and the net photosynthetic rate of the trees on B9 were the highest. The trees on GM256 had the lowest transpiration rate and the highest water utilization rate. The output of the trees on B9 was the lowest, while those on GM256 was the highest. The high-quality fruit rate of the trees on B9 was the lowest and those on GM256 was the highest. GM256 could improve early yield and high-quality fruit yield. The trees on B9 had the highest color difference L and a value, and the trees on GM256 had the highest b value. There were no significant differences in fruit shape index and solid acid ratio among the four combinations. The trees on M9-T337 had the highest single fruit weight, the trees on B9 had the highest titrable acid value, and the trees on GM256 had the highest crispness value, soluble solid value and solid acid ratio.【Conclusion】The trees on GM256 was characterized by high survival rate, strong tree vigor, high coverage rate, more branches, high fruit yield, good brittleness, high content of soluble solids and high ratio of solid to acid, sothat GM256 could be used as the rootstock of Liaoyan apple in the south of Liaoning province. B9 is not recommended for its weak tree strength although its appearance of fruits is good. Liaozhen No. 2 and M9- T337 needs further observation on the subsequent growth and fruiting performance of the trees.