Breeding report of a new sweet kernel apricot variety Zhangshuang No. 6

Abstract：Zhangshuang No. 6 is a new sweet kernel apricot variety derived from a cross of Sanganqi × Youyi. 46 hybrid seeds were produced through artificial pollination in 2007. It was initially selected in 2012 for its high rate of double kernels and good taste of kernels. The new plant variety right was granted by the State Forestry and Grassland Administration in December 2022. Compared with the maternal parent Sanganqi, Zhangshuang 6 had a higher double kernel rate and better fertility. The growth performance of this variety was stable and consistent after grafting and propagation. The tree had strong growth potential with half open posture and the branching ability was medium. The young branches were reddish-brown in the direction of sunlight. The flower buds were mainly on the bouquet of fruit branches and annual branches. The leaf was ellipse or round with a long tail tip, bicircle sharply serrated. The flower was single layer petal, the color of the lower part of the petals was white, and the proportion of complete flowers was 72%. The fruit was oval in shape with yellow ground color and rarely colored on the surface. The flesh color was orange and the pulp texture was medium with rich fiber. The average single fruit weight was 19 g and soluble solid content was 12%. The fruit nucleus was ovoid with average mononuclear weight of 2.1 g. The stone was free. The average single kernel weight was 0.85 g. The kernel was heart-shaped and plump. The shelling percentage was 41.3%. The rate of double kernel was 30%. Dried kernels tasted oily and sweet, the bitter almond glycoside content was 1 180.79 mg·kg^-1 , the fat content was 57.2%, and the protein content was 26.8%. The flower bud burst period was in late March, and the flowering period was in early April. The fruit development period was 85 d and the fruit matured in early-July in Zhang jiakou, Hebei Province. Zhangshuang No. 6 had strong cold resistance and was rarely injured at -3 ℃. Zhangshuang 6 was highly and stably productive. It had strong adaptability and could be adapted to various types of soil conditions, and could be cultivated in northern Chi-na. The free spindle and decentralized layer shape could be recommended. The spacing would be (2- 3) m× (3-4) m. The pollination trees should be needed.