AFLP Analysis Of Genetic Diversity Of Sargassum Thunbergii

Sargassum thunbergii is a common warm-temperate seaweed in China which has high economic and nutritional values. With the rapid development of sea cucumber aquaculture industry, the demand of S. thunbergii is also rising rapidly. But currently S. thunbergii culture have not formed large-scale farming, and the annual production was lower. Because S. thunbergii culture is quite dependent on the selection of seedling sources, and a large amounts of nature wild S. thunbergii was used as food of sea cucumber, S. thunbergii germplasm resources have been seriousely damaged. Therefore, the artificial cultivation of S. thunbergii is imperative, and its germplasm resources conservation and identification of genetic diversity have become particularly important.Amplified fragment length polymorphism (AFLP) was used to assess the genetic diversity of five wild populations of S. thunbergii in Dalian: SHICHENGDAO(SCD), JIANGJUNSHI(JJS), DACHANGSHAN(DCS), DONGTUOZI(DTZ), YANCHANG(YC) and a Shandong population: PENGLAI(PL). 530 loci were obtained using 10 combinations of selective primers. Of these loci, 417 were polymorphic, accounting for average 78.98% of the total. Analysis of molecular variance (AMOVA) revealed that a higher portion (76.58%) of variations was detected within populations, while a lower portion (23.42%) of variation was found among populations. The Gst value was 0.2418, which was consistent with Fst (0.2342), indicating strong genetic differentiation within populations. When integrated with the UPGMA dendrogram of the six populations, they can be clustered into two major groups. One was Shandong population, the other was Dalian populations; among Dalian populations, JJS and DCS were clustered into one group, reaching a coefficient of similarity 0.7698, but YC was lonely clustered into one group, whose coefficient of similarity was below 0.5830 comparing with the other five populations. The results showed that there was higher genetic diversity within the six populations, however it was lower among the populations; and that relationship of populations was decided not only on the geographical distance but also on the external environmental factors such as high salt and so on.Using AFLP molecular markers the study investigated the genetic diversity of S. thunbergii of five wild populations along the coast of Dalian and a wild population of Shandong Penglai. The analyzed index related to genetic differentiation within and between wild populations at the molecular lever, the genetic distance and genetic similarity between groups, UPGMA dendrogram, and the genetic diversity of the six wild populations of S. thunbergii. These will provide a strong theoretical basis and strong genetic background for development and cultivation of the germplasm resources.