A new citrus rootstock‘Pujiang Xiangcheng’（Citrus junos）

Abstract: ‘Pujiang Xiangcheng’is a novel citrus rootstock selected from wild Citrus junos resources inBaiyun village of Pujiang county in Sichuan province. Until the 1940s, many wild C. junos seedlings distributed in the mountain at an altitude of 800 to 1 000 m in Baiyun village. From 1970s, the local farmerstried to use C. junos seedlings as rootstock for citrus cultivation. They found that the grafted Citrus variet⁃ies have good compatibility with C. junos, and perform early fruiting, high and stable yield. In addition,wild C. junos has outstanding advantages such as resistance to cold and alkaline soil. Due to above charac⁃ters, it was approved as a new rootstock cultivar by Sichuan Crop Variety Certification Committee on No⁃vember, 2016, named‘Pujiang Xiangcheng’(C. junos) (No. 2016017). The cultivar has vigorous growth,spherical crown, upright and dense hard branches. Its unifoliate compound leaf is lanceolate with shortpetiole. It has solitary flower, whose lateral petals are purple from bud to bloom, with flower diameter of2.0 cm. Compared with‘Ziyang Xiangcheng’, also selected from wild C. junos resources,‘PujiangXiangcheng’has more advantages, such as taller plants, harder branches. Furthermore,‘PujiangXiangcheng’shows stable genetic characters, and reveals dramatically genetic difference from‘ZiyangXiangcheng’by SSR (simple sequence repeats) markers. The fruit is oblong to flat round, with an averageweight of 78.1 to 112.8 grams per fruit. Most fruits have flat top, obvious seal ring, with radioactivegrooves. The fruit has orange peel and rough surface, big oil cell, white spongy layer. Fruit flesh is whiteyellow,with thick capsule, which tastes very sour. There are 32 to 43 seeds in each fruit, which count forabout 10.1% of the fruit weight. It can produce as much as 3.5 to 5.5 kilograms seeds per treein one year.Plump seeds are white, smooth, with gap. Green monogerm or white polyembryony per seed has purple bigchalaza. In Pujiang county, the cultivar burgeons by early or middle March, buds by late March, bloomson April, fades by early May, fruit colors by late September, and ripe by late October, respectively. Various citrus species grafted on‘Pujiang Xiangcheng’exhibit extensive compatibility, give early bearing, high productivity with great fruit quality as well. This rootstock give high resistance to cold weather and robust adaptation to basic soil conditions. It is suitable for rootstock on different citrus varieties in main producing region in Sichuan. The fresh seeds should be sowed in loose and fertile soil immediately after 3 to 4 hours removed from fruits on Autumn. It is necessary for young seedlings to adopt heat preservation inwinter. The young seedlings can be transplanted next year when they have 4 to 10 true leaves. Fertilization for them should hold principle of applying a small amount of manure frequently. Traditional method ischosen to graft with various citrus.