Abstract:

Objective: Ａ comprehensive evaluation was conducted on growth, wood property, and stress resistance traits of Picea abies clonal population in Xiaolongshan, Gansu Province. The genetic structure, genetic diversity, and trait genetic parameters of the population were characterized based on genome-wide SNP markers, thereby providing a basis for elite clone selection and core breeding population construction. Method: A total of 136 P. abies clones were used as the experimental material to determine 15 growth, wood property and stress resistance traits. At the same time, 31 285 high-quality SNP markers retained after quality control were used to analyze population structure, genetic diversity, heritability, and genomic estimated breeding values. On this basis, the phenotypic variation, trait correlations, membership function analysis, principal component analysis (PCA), and a multi-trait comprehensive index were further integrated to comprehensively evaluate and screen the multiple traits of the clones. Result: 1) The P. abies clonal population showed a certain degree of genetic stratification. At K = 2, it could be preliminarily divided into two subgroups, with most clones exhibiting mixed ancestry. Population genetic diversity parameters, including effective allele number (N_e), observed heterozygosity (H_o), expected heterozygosity (H_e), Shannon-Wiener diversity index (I), and polymorphic information content (PIC), indicated that the population retained a certain level of genetic variation; however, H_o was lower than H_e, suggesting that the observed heterozygosity was lower than the expected level. 2) The coefficients of variation for the 15 traits ranged from 8.31% to 36.65%. Tree height (H) was most strongly correlated with diameter at breast height (DBH) (r = 0.85). Starch content was significantly positively correlated with soluble sugar content, but significantly negatively correlated with nitrogen and phosphorus contents. Heritability varied markedly among traits. Starch content, phosphorus content, budburst stage (BS), and wood density (Pilodyn value) showed relatively high heritability; modulus of elasticity, leaf dry weight (LDW), and DBH showed moderately high heritability; whereas H, chlorophyll content (CC), and nitrogen content showed relatively low heritability. 3) Using three selection methods at a 10% selection intensity, the overlap of elite clones was relatively high for growth and wood property traits but low for stress resistance traits. After retaining H and DBH, PCA of the remaining 13 traits identified seven key indicators, namely H, DBH, LDW, Pilodyn, MOE, CC, and BS. Except for H and CC, all of these key traits showed moderate or higher heritability. 4) Based on the comprehensive evaluation of these seven traits, 13 elite clones with stable overall performance were identified. Furthermore, the population could be divided into three groups based on the seven key traits, with the 13 elite clones mainly clustered in Group I. These integratively selected elite clones were distributed across different branches of the SNP-based phylogenetic tree, indicating that they covered a relatively broad genetic background while maintaining breeding potential. Conclusion: Although the P. abies clonal population showed limited overall genetic differentiation, it still retained a certain level of genetic diversity and exploitable genetic variation. The multi-trait selection strategy integrating phenotypic evaluation with molecular genetic parameters can facilitate the coordinated improvement of growth, wood property, and stress resistance, improve the stability and accuracy of elite clone selection, and provide a basis for core breeding population construction and subsequent parental optimization.

Key words: Picea abies, clonal selection, SNP markers, genetic diversity, multi-trait comprehensive evaluation