Breeding report of a new walnut cultivar ‘Luohe No. 1’ with high quality and disease resistance

Abstract：Walnut (Juglans regia L.) is a valuable woody nut and oil tree planted worldwide. In recent years, walnut has been severely damaged by anthracnose (caused by Colletotrichum spp.) and black spot (caused by Xanthomonas campestris pv. juglandis) with significant yield losses in China. Considering the severity of the diseases on walnut, a new walnut cultivar having high quality and disease resistance should be developed.‘Luohe No. 1’is a new walnut cultivar, which was bred by crossing walnut cultivar‘petro’as the female parent and‘Zhonglin 5’as the male parent in 2003 at experimental field. Six hundred and nineteen hybrid seedlings were obtained by sowing hybrid seeds in 2004. A superior individual with good eating quality, stable high yield and disease resistance was screened out in the hybrid offspring through good strain selection. From 2012 to 2018, regional tests were conducted at Luoyang, Ruyang, Yima and Qixian in Henan province. Regional tests showed that the genetic characteristics of the superior line were stable. We applied for the registration as a new cultivar in August 2018 and got identification certificate from Trees Variety Approval Committee of Henan province in December 2018, and named‘Luohe No. 1’. The tree of‘Luohe No. 1’is medium-sized with upright tree body and strong branches. The type of leaves are odd pinnate compound leaves. The leaflets are long elliptic and opposite. There are 9-11 leaflets attached along an extension of the petiole. The main veins of leaflets are asymmetric on both sides, narrow on the inner side and wide on the outer side. The fruit shape is oval. The average weight of fruit is 16.46 g. The shell thickness is 1.30 mm. The shell is relatively smooth, with a longitudinal diameter of 47.33 mm, a transverse diameter of 35.50 mm and a side diameter of 41.00 mm. The suture is slightly raised and tightly combined. The average weight of kernel is 8.38 g. The kernel yield is 50.81%. The kernel is full, yellow, taste strong, no astringency, and very easyextraction in halves. Quality is excellent. The tree germinates in late March and the female floweres bloom in middle April. Male flowers bloom earlier than female ones. The fruit development period is 126 d and it ripens in middle September at Luoyang city in Henan province. Regional tests showed ‘Luohe No. 1’is resistant to Colletotrichum spp. and X. campestris pv. Juglandis. The tree of‘Luohe No. 1’has strong adaptability and grow well at regional test sites in Henan province. This walnut cultivar can bear fruits next year after grafted, has high yield potential. Walnut trees should be planted in a deep, fertile, well-draining loam soil. The planting site should be prepared by levelling the ground and eliminating weeds. Trees should be spaced 4 m × 5 m apart. The configuration of pollinizer is the walnut cultivar ‘Lübo’. In general, the tree of ‘Luohe No. 1’need pruning young trees during their first or second year in order to determine their shape. The shape is very important and can affect production quantity, quality and ease of harvesting or other farming activities.