Effects of different rootstock- scion combinations on tree development, photosynthetic production, yield and quality of Fuji apple

Abstract:【Objective】Effects of different rootstock-scion combinations on tree growth and fruits performance in Fuji apple was studied to provide reference for the selection of rootstocks for Fuji apple. 【Methods】The nursery trees of Fuji apple with different rootstock-scion combination (Yanfu3 / T337, Yanfu3 / M9, Yanfu3 / M9 / Malus robusta, Yanfu3 / M26 / M. robusta, Yanfu3 / M7 / M. robusta, Yanfu3 / SH6 / M. robusta, and Yanfu3 / SH18 / M. robusta) transplanted in 2010 were used as materials to study tree development, branch composition, orchard structure, orchard light, leaf photosynthetic production, early fruiting, fruit quality and yield of the Fuji apple in 2012 to 2019.【Results】There were significant differences in the tree growth, branch composition, orchard structure, orchard light, leaf photosynthetic production, early fruiting, fruit quality and yield among the Fuji apple trees with different rootstock-scion combinations. The tree height, stem circumference, crown diameter and crown volume of the Fuji apple trees with self- rooted dwarfing rootstocks were significantly lower than those of the Fuji apple trees with interstock and rootstocks. The tree height, stem circumference, crown diameter and crown volume of all tested trees increased rapidly 3-5 years after planting, and then tended to increase slowly. The tree height of the trees with self-rooted dwarfing rootstocks kept stable at about 3.1 m, the stem circumference was 24 cm and the crown diameter was 180 cm. The number of branches per plant increased rapidly 3-5 years after planting, and then increased slowly. In the 4th year, the number of branches per plant of the trees with self- rooted dwarfing rootstocks was significantly higher than those of the trees with dwarf interstocks. However, 6 years later, the number of branches per plant of the trees with self-rooted dwarfing rootstocks was significantly lower than those of the trees with dwarf interstocks. SH18 and M7 combinations had poor dwarfing ability. 6 years after planting, the tree height, stem circumference and crown volume of the trees with SH18 and M7 dwarf interstocks were significantly higher than those of the other three combinations, but there was no significant difference in the number of branches per plant among the interstock combinations. With the increase of tree age, there were significant differences in branch composition of different dwarf rootstock and interstock combinations of Fuji apple. The proportion of medium and short branches of T337 and M9 self- rooted dwarf rootstock combinations was significantly higher than those of dwarf interstock combinations. The proportion of medium and short branches of T337 and M9 self-rooted dwarf rootstocks reached 44.4% and 41.5% respectively in the third year after planting. In the fourth year after planting, the proportion of short branches continued to increase, and the long branches and developing branches continued to decrease. The branch structure tended to be stable (entering the stable production period) in the fifth to tenth years after planting, and the proportion of medium and short branches kept stabile at over 75%, There was no significant difference in the branch structure between the trees of Fuji / T337 and Fuji / M9. The proportion of medium and short branches of the trees with dwarf interstocks gradually increased in the third to fifth years after planting and the increase was the highest in the fourth year. In the sixth year, the proportion of short branches of the trees with all dwarf interstocks reached the highest number. Among them, the proportion of medium and short branches of the trees with M9 rootstock was up to 68.6%, and the proportion of medium and short branches of the trees with M7 and SH18 interstock was 53.4% and 52.3% respectively. From the 6th to 10th year after planting, the branch composition of M9, M26 and SH6 dwarf interstock combinations tended to keep stable, and the proportion of medium and short branches of the trees with M7 and SH18 interstocks decreased slightly in the 10th year after planting. 3-10 years after planting, the leaf area coefficient and orchard coverage of the trees with T337 and M9 rootstocks were significantly lower than those of the trees with dwarf interstocks. The leaf area coefficient and orchard coverage of all combinations increased rapidly in 3-5 years after planting. On the contrary, the orchard light transmittance and canopy light transmittance showed a downward trend. The leaf area coefficient, orchard coverage, orchard light transmittance and canopy light transmittance of the trees with self- rooted dwarfing rootstocks changed little after 5th years and entered a stable period, while the leaf area coefficient, orchard coverage, orchard light transmittance and canopy light transmittance of the trees with M9, M26 and SH6 interstocks kept relatively stabile in the 7th year after planting. The leaf area coefficient of the trees with interstocks increased in 9-10 years after planting, and the light transmittance in the orchard and crown decreased. 3-8 years after planting, there were no significant differences in the net photosynthetic rate chlorophyll content and hundred leaves thickness. In the 9th and 10th years of colonization, the net photosynthetic rate of the leaves of the trees with M7 interstock was significantly lower than that of other combinations. The combination of Yanfu 3/T337 was easy to blossom and had the highest early fruiting. The rate of flowering plants reached 89.7% in the second year after planting. The yield per plant of 3-5 years old was 2.83, 16.44 and 30.52 kg per plant respectively. The early fruiting ability of Yanfu 3 / M9 / M. robusta was better than those of the trees with other dwarfing interstocks. The yield per plant in 3-5 years was 2.64, 12.65 and 24.77 kg per plant, respectively. The average single weight of Yanfu 3/T337 was the largest, reach-ing 286.1 g. The peeled-hardnesses of the fruits of the trees with M9, T337 rootstock and M7 interstock were higher (8.6, 8.5 and 8.7 kg · cm- 2 , respectively). The content of soluble solids of the fruits of the trees with M9, T337 rootstocks and M9 and SH6 interstocks were higher (15.2, 15.1, 15.0, 15.0, respectively). There was no significant difference in coloration index of the fruits among different rootstockscion combinations. The yield of the trees with T337 rootstock was higher than those of Yanfu 3 / M9 and other interstock combinations, and the yields of the trees with M9 and SH6 interstocks were better than those of the other combinations.【Conclusion】T337 as self- rooted dwarfing rootstock and M9, M26 and SH6 as interstock could be used in the production of Fuji apple in Yantai Area.