Breeding of a new black walnut variety BH08

BH08 black walnut is a new variety selected from Xinjiang black walnut. In 1993, Xinjiang Academy of Forestry Sciences introduced eastern black walnut seeds from Nebraska, USA for the first time. The seedlings blossomed and fruited in the 4th year, displaying good growth adaptability. In 2000, we introduced 6 strains of one-year grafted seedlings from the national black walnut breeding demonstration orchard in Luoning County, Henan Province, which were planted in the southern and the northern experimental stations of Xinjiang Academy of Forestry Sciences, and showed good demonstration results. In 2016, a variety introduced from the United States was approved by the Xinjiang Forest Tree Variety Approval Committee and named Xinjiang Black Walnut (S-SF-JN-010-2016). BH08 Black Walnut proved to be an ideal cultivar for landscaping. The nuts are small, full and rounded in appearance, with hard texture, beautiful surface lines, can be used for processing into craft jewellery development. The fruit has a pedicle about 4 cm in length, a longitudinal diameter of 22.06 mm, a transverse diameter of 20.74 mm, and a lateral diameter of 19.57 mm. The fruit base and top are protruding, and the fruit surface has dense uneven- sized protrusions and many obvious ribbing. The average weight of fruit is 13.5 g; the thickness of the shell 2.62 mm; the weight of the kernel 3.7 g; and the kernel recovery 16.96%. SSR molecular marker analysis confirmed that its genetic background is unique, significantly different from the other lines. BH08 has good ecological adaptability in Aksu region of Xinjiang and stable phenological period, with drought and salinity tolerance (pH ≤ 8.5, salt tolerance threshold 0.48%) and cold resistance (-35 ℃). The fruit matures in late September. This variety is monoecious with separate male and female flowers, and is of the female- first type. After grafting, it bears fruit in the thirdyear. It is recommended to plant the variety in slightly alkaline sandy loam or loamy soil (pH ≤ 8.0) with a water table of less than 1.5 m and a soil thickness of ≥50 cm. Direct sowing of seeds with outer seed coat 1 week is carried out before soil freezing in autumn. Bare root planting is preferred when the seedlings are 1-2 years old, at a planting density of 3 m×3 m or 3 m×4 m. It is recommended to use Xinjiang black walnut as rootstock. Whip grafting of BH08 is applied in spring, while budding used for summer. Such a graft combination enables a survival rate of above 90%. After grafting, it is necessary to strengthen the scion growth by removing sprouts from the stock and well management of water, fertilizer and weeds. Pest control should be strengthened. It can be widely used in the protection forests of agricultural areas and urban gardens in the oasis areas of the north slopes of Tianshan Mountain, the Ili River Valley and the plains of the Tarim Basin.