Breeding report of a new large-fruit-sized cultivar Huishi 2 in Chinese jujube (Zizyphus jujuba Mill.)

Abstract: Huishi 2, a new jujube bud mutant with large fruit, was selected from a Huizao orchard in the production team 2 of Aksu Experimental Forest Farm, Xinjiang by Xinjiang Academy of Forestry Sciences and Aksu Dazaoyuan jujube farmers specialized cooperative. The tree posture of this variety is half- spreading, the tree profile is globose- shaped, the tree vigor is intermediate and the trunk bark is split longitudinally. The thorn is underdeveloped, with a length of 3.31 mm. The curvatura degree of secondary shoot is approximately 140°, and the internode length is 9.1 cm. The color of current year growth is celadon. The fruit is large and nearly cylinder in shape. The vertical length of fruit is 3.48 cm, the cross length is 2.06 cm, the fruit shape index is about 1.69, and the single fruit weight at full maturity is 9.10 g. The leaf shape is oviform, being 4.5-5.8 cm long and 2.2-2.7 cm wide, with an average leaf area of 19.0 cm², and the shape of leaf margin is bicrenate. The pericarp is slightly thick, the mature pericarp is orange red, and the fruit surface is flat. The fruit core is small, and spindle- shaped, which weighs 0.41 g, and the ratio of edibility is 95.6%. The fruit has good quality, and is crispy with sweet taste. The total sugar content of semi-dry jujube is 66.11%, Vitamin C content is 1.20 mg·g^-1 , flavonoids content is 25.96 mg·g^-1, soluble protein content is 139.75 mg·g^-1 and cellulose content is 7.37 mg·g^-1. In the Aksu Experimental Forest Farm area, Huishi 2 sprouted in mid April, and about 7 d later than the standard Huizao (Zizyphus jujuba Mill.). It started to grow leaves in early May, entered the full bloom in mid and late June, came into the white maturity in early September and achieved the full maturity in mid-October. The vegetative growth period of this variety is about 206 d, and the fruit growth period is about 105 d. It is a late-maturing variety. The main pests are jujube Contarinia sp., Tetranychus truncates, flower thrips, Carposina niponensis, etc., it is more resistant to jujube fruit brown cortex and ju- jube virus disease, and the fruit cracking is relatively less. It is suitable for jujube cultivation in southern Xinjiang and other similar ecological areas. The grafted jujube tree blooms and bears fruit in the same year, and the average yield of semi-dry jujube per tree in the ninth year can reach 7.0 kg.