VARIATION IN POLYUNSATURATED FATTY-ACIDS COMPOSITION OF PERSIAN WALNUT

The variation in polyunsaturated fatty acid content of walnut (Juglans regia L.) oils was determined by analysis of samples isolated from specimens growing in four germplasm collections [California (55 cultivars), Washington (64 seedlings), China (12 cultivars), and France (20 cultivars)]. In addition, the impact of within-state geographic differences on oil composition was examined by comparing samples from three California cultivars (Ashley', 'Hartley', and 'Franquette') grown in three locations. Local environmental effects on oil composition of 'Chico' were also examined by comparing 1) samples collected from shaded and sun-exposed locations of the same trees and 2) samples collected from trees subjected to three irrigation regimes. Polyunsaturated fatty acid content, as a percentage of total fatty acids, ranged from 47.2% in nuts from PI 142323 from France to 81.0% in 'Ashley' from California. However, our data indicate that environment, genotype, nut maturity, and their interactions all contribute significantly to variation in the degree of unsaturation of walnut oil.