ANALYSIS OF GENETIC DIVERSITY IN PURPLE LETTUCE (LACTUCA SATIVA L.) BY SSR MARKERS

In this study, we analysed the genetic diversity and relationships of the leaf lettuce germplasm by SSR markers. The HPLC and Colorimeter techniques were used to measure the anthocyanin contents and colour indices of 54 different coloured Lactuca cultivars. Five colour levels of lettuce can be established for leaf grading by our correlation analysis between the colour parameters and contents of anthocyanin. The purple part in the distribution of lettuce leaves can be classified into four categories. This study provides a measure of the leaf colour traits using the scientific method. We also analysed the genetic diversity and relationship among 39 purple leaf lettuce germplasms by SSR markers. Our findings showed that the average values of Nei's gene diversity and Shannon's information index for the 39 cultivars were 0.5635 and 1.0151, indicating a low degree of genetic diversity among the tested genotypes. Cluster analysis showed that all 39 varieties were clustered into two major groups with a similar coefficient of 1.2125. The group I was divided into two sub-groups: leaf fold lettuce and erect lettuce. The first sub-group of lettuce leaf colour was purple, and the anthocyanin contents were greater than those in the other sub-group Crisphead lettuce. The group II was further divided in two sub-groups: leaf fold lettuce and erect lettuce. There were three species in the same branch with a close genetic relationship. The 39 purple leaf lettuce varieties with different SSR fingerprints could serve as cultivar-specific patterns and as an important basis for varieties identification.