Breeding report of Yuguo 1, a new dual-purpose mulberry variety for fruit and leaf use

Yuguo 1 is a high-yield and top-quality mulberry cultivar suitable for both fruit and leaf use. This cultivar originated from a natural hybrid seedling of wild mulberry. It was initially selected in 2009 from superior wild mulberry trees at the Xili Silkworm Breeding Farm (Caijiagang Street, Beibei District, Chongqing), where a progeny garden was established. In 2012, an individual with large leaves, thick leaf flesh, dense internodes, vigorous growth, high-yield, and high-quality mulberry fruits was selected. From 2013 to 2015, the biological traits of the new cultivar were evaluated, and a comparative trial was set up. Regional trials were conducted from 2016 to 2019 at five locations in Chongqing, including the Chongqing Sericultural Research Institute, Hechuan, Jiangjin, Fuling, and Wanzhou districts. In 2021, the cultivar was officially approved by the Chongqing Sericulture Cultivar Certification Committee and named Yuguo 1. The cultivar has a tall and spreading tree shape, with sturdy and upright branches, numerous lateral branches, and strong shoot growth. The fruit is purplish-black and cylindrical (a length of 3.16 cm, and a diameter of 1.63 cm), with an average single fruit weight of 3.96 g. Yuguo 1 exhibits an average fruit set rate of 91.01% and an average annual fruit yield of 39.38 t· hm-2 , which is 25.63% higher than the current main cultivar Hongguo 2. Additionally, it has an average annual mulberry leaf yield of 20.84 t·hm-2 . The fruit contains an average sugar content of 9.5°Brix, reducing sugar content of 2.91%, total acid content of 3.56 g·kg-1 , anthocyanin content of 0.10%, polyphenol content of 4.25 mg·g-1 , total flavonoid content of 5.26 mg·g-1 , protein content of 12.12%, and juice extrac-tion rate of 64.49%, indicating excellent quality. The flowering period of Yuguo 1 spans from March 10 to 30, with initial flowering occurring from March 10 to 17, full flowering from March 15 to 24, and final flowering from March 22 to 30. The mulberry fruit ripening period extends from April 11 to May 5, with peak ripening observed between April 19 and 26. Yuguo 1 has strong adaptability and is suitable for cultivation in the basins of the Yangtze River, Jinsha River, and Yellow River. It can be planted in clay, sandy loam, or loam with a soil layer thickness of 90-100 cm and has good yield potential. Yuguo 1 can be propagated by grafting, using the winter buds from late December to late January or the green branch method from April to June. In the first year, prune the main trunk to 35-40 cm in spring. In the second year, prune at 55-60 cm in summer to promote secondary branches. By the third year, prune at about 70 cm for tertiary branches. Afterward, annual winter and summer pruning after harvest should be conducted, maintaining 4000- 5000 branches per 666.7 m2 . As a dual- purpose cultivar, diseases like sclerotinia and pests like gall midges should be managed effectively. Apply annually 1700 kg of organic fertilizer, 20 kg of nitrogen, 45 kg of phosphorus, and 17 kg of potassium per 666.7 m2 , with an N∶P∶K ratio of 50∶25∶40.