Breeding report of a new grapefruit cultivar 'Gui-grapefruit No.2'

Abstract: 'Gui-grapefruit No.2' is a new grapefruit cultivar with excellent appearance. The variety wasderived from a bud mutation of‘Red-Marsh'grapefruit. The variation maternal plant was discovered forits bigger fruit size and better fruit quality, more vigorous tree and higher resistance of citrus canker, in anorchard of ‘Red-Marsh' grapefruit which was planted in 2008 in Tanle village, Wuming county, Nanning, Guangxi. This variety is a medium tree when grafted on lime rootstock, attaining a height of 2.8 m.The tree is medium vigorous with natural roundhead shape. Leaves on spring shoots are ovate, 8.13-9.81 cm long and 3.86-4.78 cm wide. The flower is large white complete flower with mostly five petals and 25 to 28 stamens, solitary or cymose. Fruiting position is mainly on the top of spring shoots. The fruit is ob-late. The fruit peel is smooth and yellowish-green without bagging vs. pink with bagging. The flesh ispink, melting, sweet and moderate sour and bitter taste, with intense grapefruit aromas and flavor. The av-erage fruit weight is 350 g and the maximum fruit weight is 390 g. The fruit shape index is 0.87. There are3-5 seeds per fruit. The fruit quality is excellent with 55.7% juice yield, 10.1% total soluble solid content, 79.41% fruit edible rate, 55 g·L^-1 total sugar content, 0.8% total acidity content, 6.87 sugar-acid ratio and 325 mg·kg^-1 vitamin C content. The fruit development period is 240 d and the mature stage is fromthe middle to late of November in Nanning area of Guangxi. The branching ability is strong. It is resistantto citrus canker etc. The fruit has very long storage life. The cold storage life is six months. Suitable cultivation area is Nanning area of Guangxi, this variety can bear fruits at the third year after planting withhigh and stable yield potential. Orchard should choose neutral sandy soil which is flat and has ability ofmoisture and fertilizer retention. Virusfree seedlings are necessary to prevent diseases from the begin-ning. Spacing in rows and spacing between rows are (2.5-3) m×4 m and the best field planting density is825 to 990 trees per hm². Fruit should be harvested timely. Great attention should be paid on the diseaseand insect preventing, especially on Huanglongbing and citrus canker.