Breeding report of a new early-ripening sweet cherry cultivar Chunshuo

Chunshuo is an excellent early-ripening sweet cherry variety selected from the natural hybrid seedling progeny of Molly. In late May 2002, over 800 naturally hybridized seeds were collected from Molly trees. In spring 2003, seeds were sown in a greenhouse, yielding over 200 seedlings. In spring 2004, these seedlings were transplanted into the cherry nursery at the Zhengzhou Fruit Research Institute. Beginning in 2007, it produced a small amount of fruit. Following a systematic evaluation of fruit characteristics, the superior individual plant coded“23-48”was preliminarily selected. It was then propagated through high grafting in the institute’s variety resource nursery. After three consecutive years (2008—2010) of comprehensive trait observation and assessment, it was officially designated as a superior strain in 2010. Chunshuo exhibits vigorous growth with an upright habit, strong branching capacity, and high flowering potential. During peak fruiting, tree vigor remains moderate. New shoots display deep anthocyanin coloration at the tips. One-year-old branches on young trees are robust, with moderate lenticel density; perennial branches exhibit reddish- brown coloration. The Chunshuo fruit is nearly spherical, and purplish-red in color with a glossy sheen. The average fruit weight is 9.2 g, with the largest one reaching up to 13 g. The average length and width measure 2.30 cm and 2.86 cm, respectively. The flesh is firm, making it well- suited for storage and transport. The fruit apex is concave, and the stem is short and thick. Soluble solids content is 16.7%, total sugars content 11.05%, titratable acids content 0.64%, and vitamin C 6.10 mg·100 g-1 . The flesh is firm with intense sweetness and acidity, excellent flavor, and good storage and transport tolerance. Chunshuo exhibits vigorous growth with an upright habit and strong branching capacity. Its one-year-old shoots are robust. As a self-incompatible cul- tivar with S genotype S1S3, it requires pollinator trees for commercial planting. Individual young trees may bear a small amount of fruit in the third year after planting, reaching peak fruiting in the fourth year and entering full production by the fifth year, yielding 1300 kg per 666.7 m2 . It primarily bears fruit on spurs and cluster-type spurs, exhibiting early fruiting, high productivity, and stable yields. It tolerates high temperatures during flowering and produces very few malformed fruits. Chunshuo exhibits outstanding disease resistance, particularly against brown spot and bacterial leaf spot. It tolerates high temperatures during flowering and demonstrates excellent resistance to fruit cracking. Sweet cherries can be cultivated in both plains and hilly regions. Suitable cultivation areas include Henan, Shandong, Hebei, Shaanxi, northern Anhui, Dalian in Liaoning, southern Shanxi, Tianshui in Gansu, and high-altitude areas in Sichuan. Select clonal semi- dwarf seedlings as rootstocks, such as ZY- 1, Gisela 6, and Lanting No. 2. Trees can planted at 2-3 m × 4-5 m spacing. Tree shapes may include modified spindle, slender spindle, or upright central leader systems. During the training years, promptly perform branch spreading on lateral branches each autumn and winter. Pruning should focus on light thinning with minimal heading cuts. Strengthen fertilizer and water management to maintain vigorous tree growth and promote the formation of cluster-like fruiting spurs. Based on the occurrence patterns of major pests and diseases, spray 5 °Bé lime-sulfur solution before budbreak to eliminate overwintering sources. After fruit harvest, apply fungicides and insecticides 2-4 times to control early leaf drop disease and various pests.