Drought tolerance evaluation of Fraxinus mandshurica in a semi-arid area

Fraxinus mandshurica Rupr. is a key forest species in Northeast Asia, primarily distributed in semi-humid regions. Given its wide range of provenances, F. mandshurica exhibits substantial genetic and phenotypic variations. To identify drought–tolerant lines, we evaluated physiological, biochemical, and growth traits of two-year-old seedlings grown in a semi-arid environment across spring, summar and autumn. Principal component analysis (PCA) of 24 trait variables yielded 10 principal components per season, accounting for approximately 85% of the cumulative variation. We developed a comprehensive drought evaluation metric (D value) for each line by calculating weighted averages of PCA scores. Cluster analysis base on seasonal D values categorized 69 F. mandshurica lines into three groups: drought-tolerant, weak drought-sensitive, and drought-sensitive. Using two growth traits, these lines were further classified into high-, medium-, and low-growth groups. From this, we identified five elite lines combining drought tolerance and rapid growth. Stepwise regression revealed that F. mandshurica employs distinct drought-tolerance strategies across seasons. We developled robust drought-tolerance evaluation models for F. mandshurica and selected five high-performing lines with dual traits of drought tolerance and fast growth. Our results provided a basis for afforestation efforts of F. mandshurica in semi-arid regions.