Breeding report of a new early-ripening yellow- fleshed kiwifruit cultivar Jinmi No. 4

In recent years, yellow-fleshed kiwifruit cultivars have become increasingly popular among consumers both domestically and internationally due to their bright fruit color and high content of carotenoids. Shaanxi Province, as the largest and most profitable kiwifruit production area in China, still mainly cultivates green-fleshed cultivars (Actinidia deliciosa), with a relative lack of yellow-fleshed kiwifruit (A. chinensis) varieties, especially early-ripening ones. In 2005, the seeds from open pollinated Guihai No. 4 fruits were collected and sowed. Therefore a population of seedlings was obtained in 2006. After many years of observation and evaluation of the characteristics of the trees and fruits of the seedling offsprings Jinmi No. 4 was found to have some significant advantageous traits: early maturity, yellow flesh, high quality and high yield. After regional adaptability testing at three sites over five years from 2017 to 2022, it was finally selected and registered in 2024. The one-year-old branches is smoothy with no hairs or only a few short pubescence on the its surface. The leaves are broad obovate and semileathery, with wavy margins and a light green color. And its flower inflorescence is a dichasial cyme, the pedicel length and the corolla diameter are 48.74 mm and 49.25 mm, respectively. The fruit is elliptical in shape, with plump fruit body, the longitudinal diameter. The transverse diameter and the fruit shape index are approximately 76.10 mm, 43.91 mm and 1.64, respectively. The average weight of fruit is 86.35 g. The skin is greenish-brown and flesh color is golden yellow. The contents of soluble solids, total sugar, titratable acidity and vitamin C in ripening fruit are 22.41%, 15.20%, 0.93% and 1390 mg·kg-1 , respectively. In Guanzhong District of Shaanxi Province, the peak flowering period is in late April, and the fruit is ripe in mid September, with a fruit development period of 140 to 145 days; and the bud break rate, branch formation rate and the fruit- bearing branch rate are, respectively, 83.23%, 59.11% and 83.47%, with short fruit-bearing branches being the main contributors (67.14%). It has a vigorous growth habit and stronger heat and cold tolerance. The fruits could be stored for more than 30 days at room temperature, and 90 to 120 days in cold storage (1.0 ± 0.5) °C. It is a diploid plant. It showed significant differences at the DNA level compared with the reported cultivars (like Nongda Jinmi, Heijin, Jinyan and Huayou). Suitable cultivation area would be the low-altitude areas of the northern foot of the Qinling Mountains and the Hanjiang and Danjiang River basins in Shaanxi, as well as in similar climatic zones; it has an average yield of 27.90 t· hm-2 in the full fruit stage. Cultivation techniques including establishment of orchards, the selection of male plants, shaping and pruning, flower and fruit management, as well as soil, fertilizer, and water management can refer to the practices used for Nongda Jinmi and Heijin. The breeding and promotion of Jinmi No. 4 could provide a new insight for optimizing the kiwifruit variety structure and for the staggered marketing of red, yellow, and green kiwifruit varieties in early, mid, and late seasons, in Shaanxi Province.