Breeding report of a new early-maturing yellow firm-fleshed nectarine cultivar Zhongyou 19 Hao

Nectarine (Prunus persica var. nectarina) is an important variety of peach in the Rosaceae family. After the 1970s, China introduced some nectarine cultivars from Europe and America, which did not meet the taste preferences of domestic consumers. Through strategic hybridization and selection protocols, Chinese pomologists have recently developed multiple high- quality nectarine varieties with strong adaptability and sweet flavor, including early maturing varieties Zhongyoutao 4 Hao and Zhongyoutao 5 Hao, medium maturing variety Zhongyou 20 Hao, and late maturing variety Zhongyoutao 8 Hao. However, the breeding of early maturing and storage tolerant varieties still relatively lags behind. Zhongyou 19 Hao is a newly released early maturing, yellow firm-fleshed nectarine bred by Zhengzhou Fruit Research Institute, CAAS. In 1999, Bei1-9 was used as a female parent and Zhongyoutao 5 Hao, a early mature and white-fleshed nectarine as a pollen donater. Among the offsprings, 99-43-58 was selected for its maturation stage in mid to late June, but the fruit surface had insufficient coloring of fruit surface. In 2005, a cross was made using Zhongyoutao 14 Hao, a early repening, white and firmfleshed with well colored surface nectarine variety, as female parent and 99-43-58 as male parent. A total of 45 hybrid seedlings were obtained that year, resulting in 16 hybrid seedlings. Seedlings were planted in spring 2006. The individual plant numbered 05-1-139 bloomed and bore fruit in 2009. Its main economic traits of the mother tree were stable in three consecutive years of observation. In 2011, the scions were collected from it for top grafting test. There was no significant difference in performance among the top grafting trees. In 2024, it was officially registered as Zhongyou 19 Hao under the non-major crop variety registration system of the Ministry of Agriculture and Rural Affairs of the Peo-ple's Republic of China, with registration number GPD Tao (2024) 410043. The main characteristics were as follows: the annual new shoots are green, the sunny side of the shoot is red, and the average internode length is 3.0 cm. The leaf length is 18.8 cm, and the width is 4.6 cm. The petiole is kidney shaped with 2-4 nectaries. The flower has five petals, with pink corolla, orange yellow inner wall of calyx tube, abundant pollens. The average fruit weight is 210 g and the maximum weight is 240 g. The fruit surface has a light yellow base color, and more than 80% dark red coloration. The flesh is yellow and extremely firm. When mature, there is no anthocyanin under the skin or near the nucleus of the fruit. The flesh is fine and sweet with little fiber. The soluble solids content ranges from 11.7% to 15.9%. The fruit nucleus is of medium size, oval in shape, with a moderate degree of brown color. The surface of the nucleus is slightly grooved, without cracked or sticky nuclei. No cracking phenomenon was found. In Zhengzhou area, the sprouting time of Zhongyou19 Hao is in the end of February and the flowering time is in the mid to late March. The fruit matures in mid June, and the fruit development period is about 70 days. The leaves fall is in mid November, and the annual growth period is about 240 days. It exhibits superior edaphic adaptation to northern China's continental climate zone, yet requires proper water management in commercial orchards to prevent water stress and soil saturation.