The Rabor Agriculture Research  Station  (RARS),  located  in  the  Kerman  province  of southeastern Iran, contains one of the largest in situ germplasm collections of Persian walnut (Juglans regia L.) in the country. In this study, the phenotypic diversity of 10 wild walnut genotypes originating in Iran and 6 foreign cultivars was examined. In 2018-2019, 13 quantitative and 18 qualitative variables were recorded for each individual, including traits related to nut and kernel morphology, kernel phytochemical composition, and tree architecture and phenology. In general, results showed that walnuts from RARS were phenotypically diverse with significant variation found across most traits examined. Results showed that the highest and lowest coefficient of variation (CV) was found for nut  shape in perpendicular to suture (CV = 80.46%), and kernel height (CV = 2.73%), respectively. Results also showed a strong positive correlation between nut weight and width (r = 0.794), kernel weight and nut height (r = 0.776), nut weight and height (r = 0.770) kernel size and nut shape in longitudinal to suture (r = 0.701), date of leaf opening and color of annual shoot (r = 0.692), and prominence of pad on suture and shape of apex perpendicular to suture (r = 0.682). Principal component analysis of quantitative variables revealed that the first five principal components (PCs) accounted for 83.61% of the total variation. Regarding qualitative variables, the first seven PCs accounted for 85.95% of the total variation. Cluster analysis based on quantitative and qualitative variables produced a dendrogram with five and eight main clusters, respectively. Grouping of genotypes was not in accordance with their geographical location. Classification of genotypes was different based on qualitative and quantitative traits. This study revealed the presence of high phenotypic diversity in the walnut genotypes from RARS supporting their value for conserving genetic resources and possible use in breeding improved cultivars.

walnut, correlation analysis, principal component analysis, cluster analysis

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia