Breeding report of a new early ripening seedless grape cultivar Nantaihutezao

Abstract: Nantaihutezao is a new, extremely early- ripening grape variety selected from the sport of Summer Black (V. vinifera-V. labrusca). It was initially selected in 2011 for its bright color and early ripening time., which shows approximately 10 days earlier sprouting than Summer Black. After regional adaptability testing at three sites (including Changxing, Nanxun of Zhejiang, and Jianshui of Yunnan) from 2016 to 2018, it was finally selected in 2019. It was a triploid European and American hybrid variety, and seedless. The tender shoots were semi-open, with medium dense hairs, and the tips were fully covered with anthocyanins. The young leaves were yellow-green with a red halo, and the upper surface was glossy, while the lower surface had medium density of creeping hairs. The mature leaves were green in color, nearly circular in shape with 3-5 lobes. The fruit cluster was cylindrical and compact, with an average length of 20 cm, an average width of 5 cm, and an average cluster weight of 250 g. The berry was round, with an average single berry weight of 2.75 g, and a fruit shape index of 1.03. The peel was purple- black, thick, and astringent- free, with a smooth surface and thick powder. The flesh was light purplein color, dense in texture, sweet in flavor, with a unique violet fragrance. After twice treatments with plant growth regulators, the average cluster weight was 656.9 g, and the average single berry weight was 8 g. The soluble solid content wa 17%-20%, titratable acidity 0.5%-0.6%, the ratio of soluble solid to acid owas 30, the hardness was 4.2-4.6 kg·cm- ², the Vitamin C content was 6.36%, and the anthocyanin content was 4.9 mg·g^-1 fresh weight in the peel. The fruit quality was excellent. The fruit development period was 100 days. Under common rain-shelter cultivation conditions in Changxing,Zhejiang (longitude 119.97, latitude 31.04), the fruit matured at the end of June to early July. The average bud burst rate was 95.0%, and the branch formation rate was 90%. It was highly resistant to salinealkali and acidic soils, and powdery mildew, but weakly resistant to gray mold compared with Summer Black. It would be suitable for cultivation in the southern regions of China and the Honghe Valley area of Yunnan. The average yield was 1 478.3 kg per 666.7 m². The suitable planting spacing would be (2.5- 3.0) m × (2.0-2.5) m. Cutting part of the flower spike, berry thinning and bagging should be recommended.