Breeding report of a new variety of Chinese jujube Wancuimi via embryo culture

Abstract: Ziziphus jujuba Mill. is one of the important fruit trees native to China. With the continuous changes in the market, fresh jujube variety has high economic benefit and great development potential. There is an urgent demand to breed new varieties of fresh jujube with both crack resistance and high fruit quality. The problem of jujube embryo abortion seriously restricts the process of jujube hybrid breeding. Embryo culture technology provides the possibility to solve the problem of early embryo abortion and offers a new way for breeding new variety. Breeders have attempted to use embryo culture to obtain jujube hybrid offspring, but so far there have been no reports on obtaining new varieties. Wancuimi is a new cracking resistant and late maturing jujube variety obtained through immature embryo culture technology after controlled hybridization of fresh jujube variety Liuyuexian with Mifengguan. The growth vigor of this variety was moderate and robust. The main trunk was longitudinally cracked, the branches were purple- red, the internodes were short, and the thorns were undeveloped. The leaf blade was ovate-lanceolate, slightly curled inward, with blunt apex, wedge- shaped base, and blunt teeth on the margin. The flowering amount was moderate, with diurnal opening. Compared with the maternal variety Liuyuexian, the internodes of this variety were shorter. This variety exhibited strong early yield performance, with an average of 1.0 fruit per hanging branch of 2- 3 year- old branches. The graftedtrees began to bear fruit in the second year. The fruits of this variety were relatively large, oblong. The average single fruit weight was 14.7 g. The fruit shoulder was flat, the top was slightly protruding, and the fruit dots were small and dense. The flesh was dense, showing significantly higher fruit strength, flesh hardness, flesh thickness, and flesh compactness than Liuyuexian. The fruit color was red, with a sweet and sour taste, and good freshness. The edible rate of the fresh jujube was 95.2%, the soluble solid content was 28.4%, the soluble sugar content was 27.5%, the acidity was 0.383%, and the vitamin C content was 3580 mg · kg- 1 . The fruit core was middle-large, long-spindle-shaped, with plump kernels and a high kernel rate. The seeds were spindle-shaped and reddish-brown. This variety had strong crack resistance, with a low cracking rate of 3.8% , far lower than the cracking rate of 38.8% of the Liuyuexian. In the Taigu county of Shanxi, bud burst was in mid-April, initial flowering in late May, peak flowering in early June, fruit coloring in mid- September, and fruit maturation in late September. The fruit development period was about 110 days, belonging to the late-maturing variety type. This variety was a fresh eating variety with compact tree body.