FRUIT AND NUT CHARACTERISTICS OF PROMISING PERSIAN WALNUT TREES IN VIETNAM

Persian walnut (Juglans regia L.) is the most economically important cultivated species for timber and nutritious nuts among 21 walnuts worldwide. Walnut has been planted in Vietnam personally in a small number of areas in Northern provinces sharing borderlines with China. The objective of this study was to survey characteristics of fruits and nuts of 15 J. regia promising trees and discuss their suitability as plus trees serving for intensive plantation. The results indicated that fruit diameter ranges 40.41-49.7 mm, fruit weight ranges 38.12-70.81 g, nut diameter ranges 24.19-34.96 mm, and nut weight ranges 9.07-25.26 g. The nut to fruit ratio for diameter ranges 57.8-70.4% and for weight ranges 20.4-35.7%. There existed positive linear relationships between fruit weight and nut weight for 10 of 15 promising trees with regression/R2 >0.5. While relationships between fruit diameter and nut diameter generally did not exist or existed with low regression (R2 <0.3). It is concluded that six of 15 promising trees could be selected as plus trees for intensive plantations through grafting technique. Those plus trees have a nut to fruit ratio for weight >30% and high regressions between fruit weight and nut weight.