Breeding of a new very early ripening Chinese jujube cultivar ‘Zaohongmi’

Abstract: Fresh jujube (Zizyphus jujuba Mill.) industry has been developing rapidly in recent years, butthere are very few early ripening cultivars planted on a large scale.‘Zaohongmi’, a new very early ripening Chinese jujube cultivar, was bred from main producing jujube areas of Taigu, Shanxi, China. It wasfound for the first time in 2000, observed and studied by area tests from 2001 to 2016. Its excellent features stood out and performed steadily in different areas of south of Taiyuan, Shanxi.‘Zaohongmi’is avery early ripening, high yielding and quality table jujube cultivar. Its fruit with bright red skin is regularin size and ovoid in shape. Average fruit weight is 10.3 g. It has high quality using for fresh eating withrich juice, crisp and delicate flesh texture. The content of soluble solid is 30.2%, the soluble sugar is28.10%, the titratable acidity is 0.63%, the vitamin C is 2 773.1 mg·kg^-1, the cAMP is 62.10 μg·g^-1, thecGMP 27.41 is μg·g^-1, the triterpenic acid is 8.86 mg·g^-1, the polysaccharose is 109.56 mg·g^-1, and theflavone is 4.98 mg·g^-1 in fresh fruit. Its stone weights 0.3 g, shapes in spindle, and has longer sharp andcoarse surface. 60% fruits have nearly full seeds. The edible rate of fresh fruit is 97.1%. It ripens and becomes crisp in late of August in middle part of Shanxi province, China with 85 d of fruit developmentdays. Fruitdrop before ripening is medium. Compared with the early ripening cultivar of‘Fengmiguan’,one of a main cultivar in China,‘Zaohongmi’ripens 10-15 d earlier with lighter fruitdrop and has moreregular ripening uniformity, fruit size and higher edible portion. Its tree is small and branching ability isweak, so it is suitable for dwarf culture and compact planting or facility cultivation. Top grafting contributes to tree cultivation. Appropriate tree forms are spindly, open-center and sparse canopy shape. Duringits blooming period, bearing branch thinning and light pinching should be done, and there should be 2-3 bearing branches per spur. Right after physiological fruit-falling period, fruit thinning should be done and4-5 fruits per bearing branch. Girdling and phytohormones should not be used or as little as possible.Yield was controlled between 4 500 kg and 5 250 kg for 2-3 year tree and below 19 500 kg for over 5 atree per hectare. Its suitable cultivated areas and conditions are districts to the south of Taiyuan and suburban plain areas or low hilly mountain with the average annual temperature of over 8 ℃, annual rainfallof less than 500 mm, the lowest temperature in winter of over -25 ℃, loam or sandy soil.