Breeding report of Jixing 2, a new high-quality and fresh-eating jujube variety with extremely late maturity

Jixing 2 is a new excellent extremely late-maturing winter jujube cultivar selected from bud mutations of Huanghua Winter Jujube. The initial selected plant was discovered in 2015, with the color and shape of jujube fruits on one branch significantly different from those on other branches; morphological observation was conducted on the mutated branch and compared with Huanghua Winter Jujube, showing stable mutation characteristics. From 2017 to 2024, through 8-year regional trials at 3 locations including Huanghua, Cang County, and Canal District of Cangzhou City, it was finally successfully bred in 2025. This cultivar has moderate tree vigor, weak branching ability, and relatively sparse branches and leaves; one-year-old Zaotou (extension shoot) are reddish-brown, perennial branches are tan, and fruiting branch groups have short internodes; lignified jujube shoots have a high degree of lignification; 3- to 5- year- old Zaogu (fruiting spurs) produce 2- 4 lignified Zaodiao (fruit- bearing shoot) per spur, with lignified fruit-bearing shoots being 19-48 cm long (26 cm on average) and bearing 10-22 leaves (14 leaves on average); leaves are long ovate, dark green, shiny, thick, with shallow serrations on the leaf margins; flowers are dichasial cymes, with yellow nectar discs at initial bloom, mature flower buds are pentagonal, with round edges and light green color, and flower bud diameters are 5.0-5.8 mm; flower quantity is small, fruit setting rate is high, lignified fruit-bearing shoots bear 5-10 inflorescences, with each inflorescence bearing 1-3 flowers; flowering begins from late May to early June; flowers belong to the night- blooming type. Fruits are oblong, with thin dark red peel, smooth fruit surface, yellowishwhite flesh, crisp texture, abundant juice, and sweet flavor; average single fruit weight is 30.81 g, maximum single fruit weight is 57.00 g, average fruit shape index is 1.10, and uniformity is 0.77. At full ma-turity, the soluble solid content of jujube fruits is 29.04%, total sugar (calculated as sucrose) is 25.60%, total acidity (calculated as malic acid) is 1.47 g·kg-1 , crude fiber is 0.9%, riboflavin is 1.08 mg·kg-1 , β-carotene is 46.80 μg·100 g-1 , iron (calculated as Fe) is 3.21 mg·kg-1 , zinc (calculated as Zn) is 2.84 mg·kg-1 , fruit peel-removed hardness is 6.08 kg · cm-2 , vitamin C content (edible part) is 353.00 mg · 100 g-1 , edible rate is 97.60%, and the quality is excellent. The fruit development period lasts 112-117 days, and it completely matures in mid-October in Cangzhou area, Hebei Province (longitude 115°42′-117°50′, and latitude 37°29′-38°57′), 7-10 days later than Huanghua Winter Jujube. This cultivar is resistant to salt and alkali and tolerant to infertile soil. The shelf life of the fruits is 3-5 days at room temperature and can be extended to 30-90 days under cold storage condition. The variety is suitable for cultivation in Cangzhou City, Hebei Province, and similar climate type areas, adult trees can bear fruits in the same year when top-grafted, enter the high-yield period 3 years after top-grafting, and have high and stable yields. It is suitable for planting in plain and mountainous areas with sandy loam, sandy soil, and loam, mainly propagated by grafting, with a plant spacing of (2-3) meters × (4-5) meters, tree shapes may adopt open heart system or small crown sparse layer system, and no pollination trees are needed.