Breeding report of a new Shatangju mandarin cultivar Yueju No.1

Abstract: Yueju No.1 is a new mandarin cultivar selected from the bud mutation of Shatangju (Citrus reticulata Blanco), a cultivar that is now the most important fresh citrus fruits in southern China. The bud variation of the Shatangju mandarin was discovered in a citrus grove located at Shakou town,Yingde city, Guangdong province in 2011. This cultivar was registered in 2017 after several years’se-lection and DUS testing. This cultivar is vigorous with upright tree shape, a strong flowering and easy fruit set ability. Leaves of Yueju No.1 are significantly larger and darker green than that of control Shat-angju cultivar. The leaf shape of this cultivar is nearly oval, approximately 9.1 cm long and 5.3 cm wide, and typically a dark-green color. The petiole is about 1.2 cm long with two small linear winged leaves. Flowers of this cultivar are slightly but noticeably larger than that of control plants, solitary and white. They are complete flower. The calyx is composed of five sepals, light green colored. The stamen length varies somewhat from about equal to the height of the pistil to very slightly higher than the pistil at full extension. The stigma is nearly circular, and the ovary is oblate. The fruit of this mutant is larger than that of control Shatangju. The fruit is oblate in shape, averaging a 0.76 fruit shape index with a smooth orange-red color peel, weighing about 86 g with a pericarp thickness of 2.5 mm; and it is easy peel and few-seed (8.7 seeds on average per fruit). The pulp is orange color and the texture is crisp, melting, and fragrant, the eatable proportion is 66%. The content of soluble solid is 13.1%-14.2%, the content of total sugar is 10.3%-11.57%, the content of titratable acid is 0.24%-0.39%, per 100 mL of fruit juice, containing the ascorbic acid is 17.3-32.4 mg. The SSR molecular markers were employed as a genetic classification approach to discriminate this new cultivar and the control Shatangju cultivar. The results showed that there were differences between two cultivars at the genetic level. There were no significantly difference in disease resistance and cold stress resistance between new cultivar and con- trol. The bud sprouting period, the flowering period and the mature period of the fruit are basically the same as that of Shatangju control. The spring bud sprouting period is early February, the flowering peri- od is early to late March, the mature period of the fruit is from mid December of this year to early Janu-ary of the following year in Qingyuan city, Heyuan city, and Guangzhou city in Guangdong province. The growing areas that suitable for Shatangju are also suitable for Yueju No.1 cultivar. The yield of Yue-ju No.1 in fruit-bearing period can reach 51 700 kg · hm^-2, that is average 12 percent higher than the yield of control Shatangju. Therefore, Yueju No.1 is a stable and new cultivar and yields higher in main growing areas than Shatangju.