Objective The genetic diversity of leaf phenotypic traits of 701 Eucommia ulmoides germplasm resources was investigated to provide theoretical support and materials for the breeding, development and utilization of Eucommia ulmoides.

MethodsFourteen phenotypic traits of Eucommia ulmoides leaves were determined. Correlation analysis, principal component analysis and cluster analysis were used to investigate the genetic diversity of leaf phenotypic traits among different germplasm.

ResultsThere were significant differences among 14 phenotypic traits of Eucommia ulmoides leaves. The coefficient of variation of leaf area was the largest (20.68%), and the coefficient of variation of chlorophyll reference value was the smallest (4.57%). The genetic diversity index of each phenotypic trait ranged from 1.90 to 2.09, and the genetic diversity index of leaf length and petiole length was the highest with 2.09.There were 26 pairs of leaf phenotypic traits that are significantly positively correlated, and 19 pairs that are significantly negatively correlated (P<0.01). There were extremely significant positive correlations among the five traits of leaf length, leaf width, leaf area, leaf circumference and petiole length (P<0.01). The cumulative contribution rate of 6 principal components extracted by principal component analysis was 89.211%. Based on 14 phenotypic traits, 701 Eucommia ulmoides germplasm were divided into 4 categories. There were significant differences in leaf phenotypic traits among various groups.

Conclusion The leaf phenotypic traits of Eucommia ulmoides germplasm resources show rich diversity, and six traits are selected as important indicators for evaluating the resources of Eucommia ulmoides germplasm resources, including leaf area, Specific leaf fresh weight, green component of leaf, chlorophyll reference value, length to width ratio of leaf, and internode length. It provides an excellent germplasm basis for the selection and comprehensive utilization of Eucommia ulmoides varieties.