Research on the Reproductive Strategies of Different Provenances/Families of Juglans mandshurica Maxim. Based on the Fruit Traits

This study systematically analyzed the fruit traits of four sources and 117 families of Juglans mandshurica Maxim. in Jilin Province. By measuring key traits such as fruit phenotype and nut phenotype, the relationship between fruit characteristics and environmental adaptability was explored, leading to the selection of superior materials with high oil content potential. The study used fruit from J. mandshurica of 117 families (random sampling) across four provenances as experimental materials and measured 13 fruit phenotypic traits, including fruit length and fruit width. Finally, principal component analysis and genetic variation parameters were conducted. The results of the variance analysis (ANOVA) indicated that except for the nut roundness index, all other traits exhibited highly significant differences among provenances and families (p < 0.01). The range of genetic and phenotypic variation coefficients for the various traits was 7.47-23.23% and 8.76-29.59%. The family heritability ranged from 0.968 to 0.988. Correlation analysis among fruit traits revealed a non-significant correlation between fruit width and seed yield, fruit type index and nut weight, kernel weight and kernel yield, as well as nut longitudinal diameter and kernel yield. However, significant correlations were observed among all other traits. The Pearson correlation analysis between fruit traits and environmental factors revealed a significant negative correlation between longitude and seed yield. Cluster analysis results, based on the Euclidean distance method, showed that materials from four provenances were categorized into three groups at a genetic distance of 5. Principal Component Analysis (PCA) revealed that the cumulative contribution rate of four principal components reached 87.00%. PCI demonstrated the highest contribution rate and included traits such as fruit length, nut longitudinal diameter, nut transverse diameter, nut side diameter, three-diameter mean, and nut weight. One elite provenance and five elite families were preliminarily selected. The realized gain for the selected provenance fruit traits was higher for fruit weight and kernel weight, with values of 2.41% and 3.67%, respectively. For the selected families, the genetic gain was highest for kernel yield and kernel weight, with values of 16.51% and 26.66%, respectively. The findings will provide insights into breeding strategies to enhance walnut oil yield. The identified traits may be used to guide breeding programs for developing high-oil-content varieties; However, further validation studies are required to confirm these traits and their applicability in large-scale breeding efforts.