Breeding report of a native early-maturing apple variety Xialimeng in Xinjiang

Xialimeng is a native cold-resistant and early-maturing variety in Yili Prefecture, the Xinjiang Uygur Autonomous Region, but its parents are unknown. It has been cultivated in Yili River basin, Tacheng, Changji and other areas for decades. Since 2006, through the continuous observation on Xialimeng it has been found that it is early-maturing with strong aroma, high yield, strong cold resistance and stable characteristics, which has the value for popularization. Then regional experiments were carried out on the basis of existing orchards to evaluate its adaptability. For seven years, in Tekes county, Tacheng City and Qitai county, the district tests were conducted by transplanting seedlings or tree grafting from 2015 to 2017, and the meticulous records were kept of the phenology, biological traits, fruit quality and cultivation techniques of this variety. The findings revealed that the biological properties of this variety were stable and suitable for promotion, thus leading to its eventual approval in 2023. The variety is a moderate tree, its crown is medium-sized and semicircle, the color of the tree is yellowish-brown, and the tree is thick and strong. The shoot has short internode. Leaf is large, oval or nearly round. Its young trees thrive vigorously, the seedling height at the grafted year is 1.0-1.2 m, and the grafted union diameter can reach up to 8.5 cm. Its fruit is medium in size, flat, round or cylindrical in shape, with a yellow-green surface, long and thick stem, a pit of rust and yellow white flesh, hard, compact, rich aroma, as well as sweet and sour flavor. The average fruit mass is 110 g, and maximum fruit mass is 118 g, with 5 cm longitudinal diameter and 5.7 cm transverse diameter. In Xialimeng fruit, 20 aroma volatile compounds were detected, comprising 10 esters, 2 aldehydes, 3 alcohols, 2 ketones and 3 other types, and the characteristic aroma components were detected, such as Butyl 2-methylbutyrate, E-2-octenal, 1-hexanol and 2-methylbutyrate hexyl ester. The first three of these components were called “fruit aroma”, and the latter is “fleshy fruit”. Soluble sugar content is 5.04%, soluble solid content is 12.9%, total acid content is 1.38 mg·g-1, and ascorbic acid content is 4.25 mg·100 g-1. And the aroma retention time is long. Fruit growth period is 110-120 days, it maturates from the end of July to the beginning of August in northern Xinjiang, and is a precocious variety, the fruit mainly grows on the medium-long fruiting branches. This variety has medium budbreak rate and branching ability. It has strong adaptability and strong resistance to barren and cold, and can overwinter upright in northern Xinjiang. However, the fruit is not suitable for durable storage, ans in the harvesting period fruits must be lightly picked, put, loaded and unloaded, according to the maturity of different harvest stages and the need for timely precooling before cold storage. It is mainly used for fresh fruit with fragrant smell, processing and special germplasm resource for hybridization. It can be cultivated in suitable-apple-producing areas of northern Xinjiang. The grafted seedlings can enter the fertile period in the fifth year, and the yield could reach 2500 kg per 666.7 m2. Direct economic benefits can reach 28 500-36 000 Yuan per 666.7 m2. The variety should be grafted through asexual propagation and wild apple should be used as the rootstock, Xinping 2 and Xinping 3 can serve as the pollinating tree. The ratio of main cultivated variety to pollinated trees should range from 5∶1 to 8∶1. Planting spacing should be 2 m×5 m. When starting an orchard, you should timely prepare the ground to ensure seedling survival, apply appropriate soil, fertilizer and water management technology, and adopt proper dwarf training and pruning technology. Dwarf culture has a certain effect on cold resistance. The appropriate training system should be central-open leader system.