Breeding report of a new Citrus cultivar Huafengtianju mandarin

Abstract: Huafengtianju (Citrus reticulata Blanco) is a new seedless mandarin cultivar selected from seedlings of Shatangju (Citrus reticulata Blanco, female parent). The seeds were collected from Shat-angju trees planted in Gonggan, Ponkan, and sweet orange, located at Shuitou town, Fogang county,Guangdong province, in 2004. The seeds were germinated in sterilized nursery soils, and the seedlings were transferred to an orchard. Seeding No.J1153 is significantly different from female parent, was found from the candidate population in 2011. This candidate cultivar was registered in 2017 after sever-al years' selection and DUS testing. The new cultivar is vigorous, upright shape. The branches are stron-ger and longer than female parent. No thorns on spring shoots. The sprouting ability of buds is better,and the intensity of flowering is greater compared with randomly selected branches in spring. Leaves of Huafengtianju are significantly wider than control with typically darkgreen color and a nearly oval shape, about 7.6 cm long and 4.5 cm wide. The petiole length is about 1.1 cm, with two linear winged leaves attached. Flowers of the new cultivar are similar to control in size, white and solitary. Each com-plete flower composes of 5 sepals. Five petals and an ovary are surrounded by 16- 20 stamens. The shape of stigma and ovary is nearly circular and oblate, respectively. The color of calyx is light green.The height of stamen is equal to that of the pistil or slightly higher than the pistil when full extension.The fruits of Huafengtianju are larger than female parent. The average weight of a medium-sized fruit is70.4 grams. The shape of fruit is oblate with an average 0.80 fruit shape index. The thickness of peri-carp is about 0.20 cm, and 75% of the pericarp is the flavedo (coloured peripheral surface) and 25% is the albedo (white soft middle layer). The fruit is seedless, with about 1 seed per fruiton average when single variety cultivation or mixed with Shatangju. The color of fruit is orange with a smooth surface, and easy to peel. The color of fruit pulp of Huafengtianju is orange and the texture of a ripe fruit is crisp and melting. The eatable proportion is 70% of the whole fruit. The soluble solid content (SSC) is 10.4%-11.0%. The total sugar content is 7.9%-8.1%. The titratable acid content is 0.25%-0.29%. The ascorbicacid content is 14.3-15.7 mg per 100 mL of fruit juice. We employed SSR molecular markers to analyze the genetic relationships between new cultivar and female parent. The results showed that there were two different bands between the two cultivars at genetic level by using SSR2F/2R and SSR7F/7R primers, respectively. In addition, the disease resistance and cold tolerance was similar between the two culti-vars. The bud sprouting period, flowering period and mature period of the two cultivars are basically the same. The period of sprouting of spring bud is at early February, the full flowering of the two cultivars appears at mid to late March, the physiological fruit drop period is from mid-April to early-June, and the fruit ripening period is from mid- December to early- January of the following year in Heyuan city,Guangzhou city and Qingyuan city, Guangdong province. The suitable growing areas of Huafengtianju is the same as that of female parent. The yield of Huafengtianju in fruit-bearing period can reach 53 100 kg·hm-2, 15 percent higher than Shatangju cultivar on average.