Breeding of a new apple rootstock ‘Y-3’

Abstract: The rootstocks had a significant impact on the grafted varieties for tree size, yield, quality andresistance, etc.‘Y-3’was selected by Pomology Institute of Shanxi Agricultural Academy. It was derivedfrom Malus baccata（L.）Borkh. in Northwest of Shanxi province, China. Its botanical characters were simi⁃lar with the common Malus baccata. Leaf was broadly ovate, wrinkled, anti-rolled which were the most obvious sign. Fruit was spherical, 0.9 cm diameter, red, calyx, calyx depression with circular rust. It was ini⁃tially selected in 2001, seeds were sowed, 200 thousand seedlings were planted and grafted different vari⁃eties in 2002, 575 grafting units blossomed in 2004,‘Y-3’was one of them. Some traits were observedsuch as potential growth, successive bearing ability, cold and drought resistance of the grafted scion from2005.‘Y-3’had good performance. The influences on the different cultivars were continued to evaluateas interstock because of its weak rooting ability from 2008.‘Y-3’showed better traits than the commonMalus baccata. It was examined and approved by Shanxi Forest Variety Committe in 2016, over sevenyears regional adaptability testing at four places (including Datong, Yuci, Yicheng, and Yuncheng). Itshowed a high value in apple cultivation by many regional trials, some good traits as follows: First, 7-yearoldtree height was 473 cm grafting‘Fuji Nagafu No. 2’as interstock, belonged to semi-dwarfed root⁃stock, showed strong growth potential, robust, consistent. Second, it had flowering and fruiting ability earli⁃er 2 to 3 year than the standard rootstock, yields of‘Fuji’in the fourth year were 2 475 kg·hm-2, but out⁃put was zero from the common northwest Shanxi baccata. Third, it had strong cold, drought and disease re⁃sistance than the standard rootstock. Four, the grafted‘Fuji Nagafu No. 2’had excellent fruit quality, thecontent of soluble solid was 15.2 percent, the content of soluble acid was 0.392 percent, the hardness was8.3 kg per square centimeters, the fruits had very long storage-life within 0 ℃, cold storage life was oversix months. Five, it had good grafting compatibility with both the rootstocks and the cultivars such as‘Fuji Nagafu No. 2’,‘Danxia’,‘Gala’, never showed wind folding, trunk lodging and other incompatibilityphenomenon. It should be pay attention to some problems when‘Y-3’was used. It was adapted to theLoess Plateau or the regions with similar climate, especially suitable for mountains and hills area, andshould be carefully used in saline area.‘Y-3’was only used as interstock until now because of its weakrooting ability, while the interstock length was about 20 cm. It was the suitable density when 840 to 1 005trees were planted per hectare. Pollination trees must be utilized which were planted every line or singleseedling about 15 percent of the whole‘Y-3’orchards. The trunk of tree used‘Y-3’interstock shouldbe maintained 1 to 1.2 m with spindle or small canopy shape, based mainly in the summer pruning includ⁃ing engraved bud, twisted tip, bent branches, and other measures, while opened the light path by thinningin winter pruning. It was similar to common orchards such as fertilizer and water management, fruit management, disease and pest control, etc.