Breeding report of a new high-oil-content walnut cultivar Long Bofeng No. 1

Abstract：Long Bofeng No. 1 is an early-ripening, high-yield and high-oil-content walnut. The seedling was selected from the‘Longnan spike walnut population’. It was initially selected in 2011 for its extremely high yield and spike-bearing-fruit trait. In 2016, it was selected as the superior line and temporarily named as Gangu Dui Spike. From 2017 to 2023, retests were carried out in Wudu, Chengxian and other places in Longnan City, and the comprehensive characteristics were excellent. In December 2023, it was granted the Plant Variety Rights by the National Forestry and Grassland Administration and named as Long Bofeng No. 1. This cultivar is a deciduous tree with medium size, semi- open posture and natural semi-circular crown. Mixed buds are round, and male flower buds are bare buds, cylindrical and scaly. Odd pinnate compound leaves are 47.3 cm long, compound petiole is 27.42 cm long, the number of leaflets is 7-11, and most ones are more than 9. Leaflets are long oval, 17.18 cm long, 7.85 cm wide, and 0.26 mm thick. Leaf is dark green with slightly- pointed tip and entire margin. Most of the fruits are spike-bearing status, and fruit surface is green without hair, but with yellow-white and denser fruit dots. The nut is round, the nut weight is from 10.6 g to 12.7 g, the kernel weight is from 5.8 g to 8.1 g, the shell thickness is from 0.94 mm to 1.15 mm, and the kernel ratio accounts for 55.0% to 63.6%. The nut shell is smooth, the longitudinal diameter is from 33.8 mm to 35.3 mm, the transverse diameter is from 30.1 mm to 33.6 mm, and the side diameter is from 31.0 mm to 35.2 mm. The suture is flat and tightly combined. The kernel is full, light yellow colored and oily flavored without astringency. The fat content is 68.6%, the protein content is 17.3%, and the nut quality is excellent. The bud break of the cultivar happens in middle March, the male flowers enter full bloom in late March, the female flow-ers enter full bloom in early April, the fruits mature in early September, and the leaves fall in late November in Wudu, Gansu province. Long Bofeng No. 1 shows resistance to Xanthomonas arboricola, Colletotrichum gloeosporioides and Brown apical necrosis diseases. The tree has strong tolerance to drought and barren conditions. The tree of Long Bofeng No. 1 is suitable for planting in Qinba Mountainous Areas and somewhere with similar ecological conditions. It can be planted productively in Longnan, Gansu province. This variety can bear fruits next year after planting, and has high yield potential. The average yield per 666.7 m2 in the fourth and fifth year after grafting is 188.32 kg and 230.12 kg, respectively. Long Baofeng No. 1 can be planted after the grafted seedlings have dropped leaves in autumn before the soil freezes or after the soil thaws in spring before the bud break of grafted seedlings. The planting spacing in plain land is generally (7-8) m × (7-8) m, and that in hilly and mountainous areas is (5-6) m × (6-7) m. The preparation of big planting hole is often required, and the size should be 1.0 m × 1.0 m × 1.0 m.