Analysis and Comprehensive Evaluation of the Phenotypic Diversity of Hydrangea Germplasm Resources

The hydrangea, a traditional ornamental flower in Chinese history, holds significant ornamental and practical value. This study conducted genetic diversity, correlation, clustering, and principal component analyses on 26 phenotypic traits across 190 hydrangea germplasm resources, providing theoretical foundations for future breeding and germplasm innovation. Results revealed that the coefficient of variation (CV) for quantitative traits ranged from 23.54% to 121.87%, with the CV for sterile flower calyx number being the highest. Diversity indices for quality and quantitative traits were 0.3143-1.3671 and 0.6134-1.4507 respectively, indicating greater genetic diversity than quantitative traits. These findings demonstrate rich phenotypic diversity and extensive trait variation in hydrangea germplasm resources, suggesting substantial breeding potential. Correlation analysis showed 14 pairs of traits exhibited highly significant positive correlations, while 7 pairs demonstrated significant positive correlations, indicating inherent phenotypic associations. Clustering analysis divided the 190 hydrangea varieties into five groups, with plant height, leaf length, leaf width, sterile calyx diameter, and sterile flower calyx number being key phenotypic traits for group classification. Principal component analysis revealed that the first four principal components (PCs) with cumulative variance contribution exceeding 74.12% captured most information, effectively reflecting fundamental characteristics of hydrangea varieties. Comprehensive evaluations ranked Group V hydrangeas as the most ornamental, followed by Groups IV, III, and II, while Group I hydrangeas showed the poorest ornamental performance. These findings establish a foundation for developing new hydrangea varieties with superior overall characteristics and high ornamental value.