Effects of Seasonality and Scion on Grafting Persian Walnut in Vietnam

Abstract

Persian walnut (Juglans regia L.) is one of the most economically important cultivated tree species worldwide, valued for both its high-quality timber and nutritionally valuable nuts. Walnut kernels are also recognised for their potential health-promoting properties, owing primarily to their high antioxidant capacity and substantial concentration of omega-3 (ω-3) fatty acids. Therefore, vegetative propagation by grafting is urgently needed in Vietnam to produce seedlings from superior genotypes with high nut productivity and quality. In this study, the side-stub grafting technique was applied in three seasons (October, December, and February) using two scion age classes (< 8 months old and 9-12 months old). The experiments were conducted in a completely randomised design with three replicates, each consisting of 35 rootstocks. The results indicated that grafting season and scion age significantly affected survival rate and shoot growth at 4 months after grafting. Scions aged 9-12 months resulted in a higher survival rate and greater shoot growth than scions aged < 8 months. The highest survival rate, 64.8%, was observed after December grafting with 9-12-month-old scions, followed by 58.1% after February grafting and 49.5% after October grafting. The lowest survival rate, 34.3%, was observed after October grafting with < 8-month-old scions. The greatest shoot growth, 36.8 cm, was observed after December grafting with 9-12-month-old scions. It is concluded that the side-stub grafting technique should be used for walnut grafting, with rootstocks aged 1.5-2 years and having a stump diameter of 1.5-2.0 cm.