Breeding report of a new late-ripening sweet cherry cultivar Wanmilu

Abstract: Wanmilu is a newly released late-ripening sweet cherry cultivar, which was selected by embryo rescue from the naturally pollinated seeds of sweet cherry Stella at the Changli Institute of Pomology, Hebe Academy of Agriculture and Forestry Science. In 2002, over 670 seedling seeds of Stella were collected through natural pollination, among which 510 hybrid seedlings were obtained using embryo rescue technology in 2003. Among them, ST793 was first selected in 2008 for its big fruit size, hard flesh and sweet flavor. Regional adaptability tests were performed in Changli, Laoting and Luannan counties in Hebei province from 2012 to 2017. The results were good, and it was finally examined, approved and named as Wanmilu in 2020. The trees of Wanmilu are moderately vigorous, with high bud break rate and branch development capability. Annual shoots are brown. The average length of annual shoots is 100 cm and the internode length is 4.7 cm. Leaves are elongated ellipsoid, acute apex with small biserrate margin. There are 1-4 flowers within each inflorescence. The flower is white, and the relative position of petals (5-6) is overlapped, petals are oblate in shape, and stamens are slightly higher than pistil with more pollen grains. The fruit of Wanmilu is heart-shaped, covered with purplish red, and the surface is glossy. The average fruit mass is 9.2 g and up to 14.2 g for the maximum one. The fruit flesh of Wanmilu is red, crisp, thick, juicy and sweet. The fruit quality of Wanmilu is excellent with sweet taste, the soluble solids content is 18.12%, the soluble sugar content is 11.0%, the titratable acid content is 0.46%, and the peeled flesh firmness is 2.18 kg · cm^-2 . The first flowering date of Wanmilu is in early April, the fruit can be harvested in mid-June, and the fruit development period is about 62 d in Changli area, Hebei province. In general, grafted seedlings will bloom and bear fruit in the third year after planted, and reach full fruit period in the fifth year. The yield of quinquennial and septennial grafted plants is 705.0 kg and 830.0 kg per 666.7 m2 , respectively. Wanmilu has a wide adaptability, it has better stress resistance, such as strong barren tolerance, cold resistance, resistance to leaf spot disease and early defoliation disease. For cultivation techniques, the spacing between trees and between rows is (2-3) m × 5 m, and summer pruning should be emphasized for balancing tree vigor and promoting fruit. Wanmilu is a good cultivar and suitable for planting inside the Hebei area, and was certified (Register No: Ji S-SV-CA-015-2020) by the Evaluation Committees of Hebei Province in 2020.