Genetic diversity and relationships of the brown alga Undaria pinnatifida cultivated along the Dalian Coast as revealed by amplified fragment length polymorphism markers

In this study, the amplified fragment length polymorphism (AFLP) method was employed to estimate the genetic diversity of young sporophytes belonging to six Undaria pinnatifida populations collected from five seaweed cultivation farms along the Dalian Coast of China in 2008. A total of 397 loci were detected using ten combinations of selective primer pairs. Of these, 302 of which (76.07 %) were polymorphic, which was mainly caused by the 40 accessions of two populations collected from the LWT (44.08 %) and the JST (44.58 %) farms. According to the UPGMA dendrogram and biplot of principal component analysis, the 40 accessions represented high intra-population genetic diversity and far relationship from all of other populations. In contrast, the accessions from the other populations (HK, MS, LS, and QD) represented high intra-population similarity. The four populations may have originated from the same introduced U. pinnatifida strain. Analysis of molecular variance showed that a higher proportion of genetic variation resided among the populations (63.56 %) than that within populations (36.64 %). It is hypothesized that the differences in genetic traits, as well as the mixed mating system and reduced gene flow were the primary reasons that caused the high genetic variation among populations and the high similarity between accessions within the population. However, the genetic diversity of the partial U. pinnatifida cultivar populations in Dalian farms has been decreasing in the past years, which poses a potential risk of germplasm degradation in cultivation. In addition, the breeding techniques of cultivated U. pinnatifida in China and the application of AFLP in Undaria are discussed in this article. Based on the results, the identified polymorphic markers could be used for genetic improvement of the species through marker-assisted breeding and the results also provide excellent information for selecting indigenous gametophyte resources from Dalian farms using different breeding methods.