Breeding report of a new high-columnar cylindrical navel orange variety Jinzhongcheng

Jinzhongcheng is a new bud sport variety of Changhong Navel Orange [Citrus sinensis (L.) Osbeck] discovered in Baiyangping Village, Guojiaba Town, Zigui County and selected by the breeders at Huazhong Agricultural University. The molecular marker technology was employed to identify the identity. The results confirmed that it was a bud sport of Changhong Navel Orange. The fruit exhibited an oblong-elliptical morphology (fruit shape index ＞1.10) and was characterized by vivid, reddish-orange rind coloration. With an average fruit weight exceeding 200 g, the fruit demonstrated fine and smoothy oil glands, crispy and tender flesh with excellent juiciness, and a distinctive aromatic profile. The fruits ripened in late November and had excellent storage capability. The fruits displayed distinctive morphological characteristics, such as unique tall cylindrical fruit shape and notably larger size compared with its Changhong Navel Orange. The tree exhibited an open growth habit with a natural open-center canopy, demonstrating vigorous growth and producing 3-4 times of shoot growth annually. Jinzhongcheng predominantly bore fruits on leafy shoots, and all the spring, summer, and autumn shoots had the potential to develop into fruitful branches due to their high Flower bud differentiation ability. This cultivar was characterized by broadly lanceolate leaves with distinctive winged petioles, and exhibited a strictly annual flowering cycle. Its flowers consisted of 5 white petals. It demonstrated distinct phenological phases in Zigui County: the budbreak started in early March, followed by spring shoot emergence in mid-to-late March. The flowering commenced in mid-to-late April, reaching full bloom in late April. The fruit underwent two physiological fruit drop phases - the first in early May and the second in mid-to-late May. The summer shoot development occured in mid-to-late May, and the autumn shoot development in mid-to-late July. The fruits began color change around mid-September and reached harvest maturity approximately in mid-December. Jinzhongcheng grew well when trained to an open- center form, demonstrating optimal fruit production on spring shoots and early autumn shoots. The post-fruiting magnesium deficiency commonly occurred and required timely supplementation. The fruit quality parameters of Jinzhongcheng were as follows: a long-fruited morphology (fruit shape index 1.42), orange-red rind with tight adherence (difficult to peel), and complete seedlessness. The biochemical analyses revealed its premium quality attributes, including 15.03% soluble solids content, 1.29% titratable acidity, average fruit weight of 396.88 g, vitamin C concentration of 58.49 mg · 100 g- 1 flesh, and 77.41% edible portion. Under containerized cultivation, the trees typically initiated fruit production in the third year, reached commercial yields in the fifth year, with productivity increasing from initial yields of 9000 kg·ha-1 to exceeding 37 500 kg·ha-1 at peak production. Jinzhongcheng exhibited moderate resistance to citrus bacterial canker (Xanthomonas citri subsp. citri) and citrus tristeza virus, with no exceptional disease susceptibilities observed under standard cultivation conditions. The primary pest management should focus on controlling aphids (Aphididae), and citrus red mites (Panonychus citri). Originally developed in Hubei Province, this cultivar showed optimal adaptation to navel orange production regions across Hubei and other ecologically comparable areas with similar conditions.