Comprehensive evaluation of Bougainvillea germplasm resources based on principal component analysis and membership function method

【Objective】This study aimed to comprehensively evaluate Bougainvillea germplasm resources in the dry-hot valley of the Jinsha River， providing theoretical reference for superior variety selection and new variety breeding of Bougainvillea in the dry-hot valley of the Jinsha River.【Method】A total of 18 Bougainvillea germplasms were taken as research objects to measure 11 cultivar traits and five pigment content indicators. Public scoring and grouping by color category were performed. Comprehensive evaluation of Bougainvillea germplasms was conducted based on analysis of coefficient of variation （CV）， cluster analysis， correlation analysis， principal component analysis （PCA）， and membership function analysis.【Result】The 18 Bougainvillea germplasms were divided into purple group， red group， orange-yellow group， pink group， and white group，and the CV of quantitative traits ranged from 28.05%-39.93%， with the largest CV for leaf width at 39.93% and the smallest CV for bract width at 28.05%. The CV of pigment content ranged from 26.52% to 46.62%， with the largest CV for procyanidin content at 46.62% and the smallest CV for chlorophyll a content at 26.52%. Correlation analysis results showed that the procyanidin content had extremely significant negative correlations with betacyanin content and flower color （P<0.001）， with the coefficient of correlation of -0.87； flower color had an extremely positive correlation with betacyanin content （P<0.001）， with the coefficient of correlation of 0.88； public scoring had significant （P<0.05） or extremely signficant （P<0.01） correlations with flower color， leaf length， procyanidin content， and betacyanin content， with the most pronounced correlation with flower color. Cluster analysis results showed that the 18 germplasms into four major groups， among which Group Ⅱ only included Bougainvillea cv. Miss Manila， demon-strating that this cultivar showed greater uniqueness compared with other germplasms； the 11 cultivar traits and five pigment content indicators were divided into four major categories: the first and second categories showed trait characteristics， and the third and fourth categories showed pigment content characteristics. Principal component analysis（PCA） showed that， six principal components from the first to the sixth principal component were extracted at the standard of eigenvalue greater than 1， with the cumulative contribution rate of 82.85%， and the traits that exhibited the highest factor loadings across the six principal components （PC1-PC6） were flower color， bract width， leaf length， leaf width， leaf color， and chlorophyll a content. By calculating the membership function values， Bougainvillea cv. Killie Campbell had the highest score. According to calculation combined comprehensive PCA with membership function method， the 18 Bougainvillea germplasms were divided into four grades， and the Grade I included Bougainvillea cv. Miss Manila， Bougainvillea cv. Mrs. Butt， and Bougainvillea cv. Killie Campbell.【Conclusion】According to comprehensive evaluation of PCA and membership function method， three Bougainvillea cultivars （Bougainvillea cv. Miss Manila， Bougainvillea cv. Mrs. Butt， and Bougainvillea cv. Killie Campbell） have high scores. As they have big bracts， big leaves， and bright bracts， they are suitable to be popularized and cultivated in the dry-hot valley of the Jinsha River.