Breeding report of a late-ripening and cold-hardy pear cultivar Jiyu

Jiyu (original code: 99-1-3) is a new late-ripening, cold-hardy pear cultivar developed by the Institute of Pomology, Jilin Academy of Agricultural Sciences. It was selected from hybrid population of a cross between Hanxiang (female parent) and Qiyuesu (male parent) made in 1999. 212 viable seedlings were obtained in 2000. The seedlings started fruiting in 2007. In 2012, 99-1-3 was designated as a primary strain based on its superior fruit appearance and excellent internal quality. Accession 99-1-3 progressed to secondary selection in 2013, compared with the control cultivars Hanxiang, Jixiang, Pingxiang and Jinxiangshui. In 2015, expert validation confirmed its sustained trait stability and exceptional cold hardiness. From 2018 to 2023, the regional trials across Jilin Province and ecologically analogous zones confirmed consistent excellence in cold hardiness, broad adaptability, disease resistance, high yield potential and premium fruit quality. After DUS test, it received national cultivar registration (Certificate No. GPD Pear [2024] 220005) from the Ministry of Agriculture and Rural Affairs, China in December 2024, and was officially released as Jiyu. This cultivar had a vigorous, upright-spreading habit, achieving heights of 5 m at maturity, with pronounced apical advantage and semi- erect scaffold branching. The color of 1-year-old shoots was reddish-brown with a mean internode length of 4.31 cm. The dormant leaf buds exhibited an obtuse-acute apex and were obliquely oriented along the shoot axis. The mature leaves were elliptic (10.08 cm length × 8.37 cm width), exhibiting dark green coloration, with truncate bases, acute apices, absent stipules and sharply serrated margins. The flowers were borne in corymbose inflorescences (7-8 florets per cluster), with pentamerous white petals and low pollen production. The fruits exhibited a globose conformation with an average single fruit mass of 153.0 g, displaying yellow ground color overlaid with a red blush on sun-exposed aspects. The flesh was white with minimal stone cell, a compact core and fine-textured crispness at harvest. Following postharvest ripening for approximately 10 days at ambient temperature (20 ℃ ), the flesh became soft (flesh firmness: 0.49 kg· cm-2 ). The fruits delivered a harmonious sweet-sour flavor with distinct weak aroma. The soluble solids content (SSC) was 15.30%, the soluble sugars content was 8.59%, and the titratable acidity was 0.33%. The fruit development required approximately 144 days from full bloom, reaching commercial maturity in late Septemberin Gongzhuling, Jilin (43.5° N, 124.8° E). Under ambient storage, the fruits retained premium quality for 10-20 days until flesh firmness declines. This cultivar exhibited exceptional cold- hardiness, validated through 20- year field observations encompassing multiple natural freezing events. It maintained undamaged growth in normal winters, with only minimal branch injury occurring during extreme frost episodes. This cultivar demonstrated significant resistance to pear leaf blotch, while exhibiting minor susceptibility to pear scab with little leaf incidence. It could be introduced for trial planting in the areas with frost free period over 135 days, effective accumulated temperature (over 10 ℃) over 2800 ℃. The sandy soil or loam soil were preferred for cultivating this variety, with pH 6.0-7.5. Pyrus ussuriensis Maxim. should be suitable rootstock. The tree shape should be spindle form or multi-layered open-center canopy. The pear varieties Hansu, Hanhong and Pingxiang could be used as Pollinizers for it.