Genetic diversity analysis of germplasms based on phenotypic traits for Lactuca sativa var. angustata

【Objective】 The genetic diversity of the stem lettuce germplasms in Sichuan was identified by the phenotypic traits, in order to provide theoretical basis for effective protection and utilization of the stem lettuce germplasms in Sichuan.【Method】 In this study, 108 stem lettuce germplasms collected from different areas in Sichuan were carried out the analysis of the genetic diversity, principal component and cluster analysis using the 17 main phenotypic traits.【Result】 The results showed that the phenotypic traits of 108 stem lettuce germplasms displayed different degrees of diversity. The genetic diversity index(H') of 8 quality traits was from 0 to 1.10, the basal part shape of cauline was heart-shaped, and the attachment mode of cauline leaves was without petiole, so H' was 0, and the H' of skin color of enlarged stem was the highest. H' of 9 quantitative traits ranged from 1.85 to 2.03 and variation coefficient ranged from 0.07 to 0.24. H' of enlarged stem length and variation coefficient of gross weight were the highest. Four principal components were extracted and the cumulative contribution rate reached 73.79% including 12 phenotypic traits. The 108 stem lettuce germplasm resources were divided into three clusters, clusterⅠcontained germplasm resources for the medium enlarged stem length and diameter, cluster Ⅱ contained germplasm resources with long and thick enlarged stem and heavy weight, they were potential high-yield germplasms, and cluster Ⅲ contained germplasm resources with dense internodes.【Conclusion】 The stem lettuce germplasm resources in Sichuan have high level of genetic diversity but low genetic index of some quality traits, which indicates that collection and protection of the stem lettuce germplasms need to be strengthened. Evaluation and utilization of stem lettuce germplasm resources are helpful for high-yield breeding and filling up the types lack in Sichuan market. Cluster Ⅱ could be used to breed high-yield varieties, and cluster Ⅲ could be used to breed varieties with purple and oblong leaf which are lack in Sichuan market.