Evaluation of genetic diversity in several populations of medicinal Milk thistle using molecular marker

Milk thistle (Silybum marianum L.) belongs to Compositae family, is a medicinal plant with unique pharmaceutical properties for treating liver diseases and grows throughout various geographical areas in Iran. In this study, SCoT markers were employed to investigate the genetic diversity of 36 samples of milk thistle from different geographical regions of Ilam and Khuzestan provinces. A total of 146 fragments were amplified and 69% of them were polymorphic. The most amplified fragments were related to the SCoT10 with 12 fragments and the lowest amplified bands were related to the SCoT22, SCoT47 and SCoT55 with 6 fragments. Mean number of amplified bands for primers was 8.58, while the mean number of polymorphic bands was 6.00. Polymorphic information content and discrimination power (PICD) varied between 0.089 in SCoT22 and 0.219 in SCoT31 with an average of 0.151. Similarity matrix was generated using the Jaccard coefficient, Cluster analysis was carried out by UPGMA algorithm and Principle Coordinate Analysis. According to cluster analysis, Milk thistle samples were divided into 3 groups. Based upon similarity matrix, the lowest similarity (0.44) was found for two samples from Eyvan and Behbahan and also the highest similarity (0.92) found between two samples from Mian-Ab within the same geographical region. Analysis of molecular variance (AMOVA) showed that a larger proportion of genetic variation (89%) belonged to within the populations, while only a small proportion (11%) observed among the studied populations. The results finally indicated high genetic diversity among the studied genotypes.