Genetic diversity analysis and comprehensive evaluation of Lolium multiflorum based on phenotypic traits

In this study, diversity analysis, correlation analysis, cluster analysis, principal component analysis, and comprehensive evaluation were conducted on 15 phenotypic traits of 114 Lolium multiflorum germplasm to investigate the genetic diversity of phenotypic traits in L. multiflorum germplasm resources, screen excellent germplasm resources, and construct a reliable, comprehensive phenotypic evaluation system. Results showed that the coefficient of variation of the 15 phenotypic traits of the L. multiflorum germplasm resources ranged from 5.20% (flowering time) to 26.15% (dry weight), the genetic diversity index ranged from 1.909 4 (dry weight) to 2.0851 (crown diameter), and the broad-sense heritability ranged from 47.25% (fresh weight) to 83.72% (internode diameter), with significant or highly significant correlations among various traits. Cluster analysis revealed that the 114 germplasm resources could be divided into five groups: Group Ⅰ (excellent comprehensive performance), group Ⅱ (average comprehensive performance), and group Ⅲ (poor comprehensive performance) were all medium-late flowering type, group Ⅳ was the late flowering and high-tillering type, and group Ⅴ was the early flowering and low-tillering type. Principal component analysis showed that the 15 phenotypic traits could be summarized into 3 principal components with a cumulative contribution rate of 78.642%. The crown diameter, leaf width, growth period, internode diameter, tiller number, and individual hay yield were the main factors affecting the differences in L. multiflorum germplasm resources. Twenty germplasm materials with excellent comprehensive performance were selected by using the Z-value. The top five materials belonged to group Ⅰ, and the last four belonged to group Ⅲ. Of these, 14 out of 15 traits showed a highly significant correlation with the Z-value. Using the Z-value as the dependent variable y and the 15 correlation indicators as the independent variable x, regression analysis was conducted to screen out 8 independent traits comprehensive evaluation indicators. These results provide theoretical support for discovering and breeding excellent L. multiflorum germplasm resources.