Breeding of a extremely late-ripening Chinese jujube cultivar 'Aoxue'

Abstract: ‘Aoxue'is a new extremely late-ripening Chinese jujube cultivar for dry and fresh fruit which was selected from the bud mutation of‘Jinsixiaozao'in Laoling. It was initially selected in 2005 for its high natural fruit set rate, long fruit growth period, late maturing, high yield and quality, etc. After four years regional adaptability testing at three sites(including Laoling, Wudi and Juxian) from 2010 to 2014, it was finally selected in 2015. The tree is vigorous with ramose crown and open tree gesture. Perennial branches are grayish brown. Biennial branches are brown green and smooth. Annual branches are red brown. The leaves are large and lanceolate. The average leaf weight is 0.31 g and the average leaf longitudinal diameter is 7.59 cm and the average leaf transverse diameter is 3.36 cm with obtuse teeth. The fruits are elliptic, having a smooth red skin with white-green flesh. Flesh texture is delicate, succulent, with a pleasant sweet flavor. The average fruit weight is 5.63 g and the maximum fruit weight is 9.39 g. The average fruit longitudinal diameter is 2.65 cm and the average transverse diameter is 2.12 cm with small stone.The edible rate, the dry rate, the total sugar content, the titratable acid, the sugar acid ratio and vitamin C content of fruit are 95.1%, 51.6%, 35.1%, 0.625%, 56.16 and 4 060 mg·kg^-1, respectively. The fruit development period is more than 150 d and it matures at the mid November in Dezhou area of Shandong province. The average number of inflorescence and fruit is 3.5 and 9.3 per branch. 8 years after grafting, the average yield of‘Aoxue'is 19.76 kg, equivalent to 1 659.84 kg per 666.7 m². The fruit didn't fall off after maturity with high quality and high yield.‘Aoxue'is resistant to drought, cold and disease. Suitable cultivation area is jujube cultivation area,especially Shandong, Henan, Hebei and other‘Jinsixiaozao'cultivation areas. Planting method and density depend on the purpose of the establishment and plantation condition. Spacing in the rows and spacing between rows are(2-3) m ×(3-4) m on the plains. Pruning the youth tree light for more fruiting branches and thinning the dense branches in the inner part of the fruiting tree.