| Kelp is an important economic algae, widely used in food, medicine, chemical industry and so on. Laminaria japonica of china were transplanted from Japan. In addition, it has been successfully cultured and naturally grows on the seabed in Liaoning, Shandong and other places. Due to the different environmental conditions, the form of individuals produce a number of variations, but they all belong to the same species. Most of cultivated varieties are interspecific hybrids, 1 / 2 or more of the genetic bases of their germplasm are from the original population Laminaria japonica. Single species exist great threat of genetic vulnerability. On the side, Laminaria farming adopts multi-species mixed culture and seedling culture in the same period and other methods. After the process of self-production or inbreeding, good characters of varieties will have a clear recession. The identification of germplasm of Laminaria still rely on the experience of technical staff to determine, to further increase the impact of the hybrid Seed and variety degradation in useful life of farming varieties. With the development of Laminaria farming, these issues become increasingly prominent and have become an important factor of constraining the development of seaweed farming. Therefore, studing the genetic diversity of Laminaria use modern molecular marker technology will help to the development and utilization of Laminaria germplasm resources.The amplified fragment length polymorphism (AFLP) was used to estimate population genetics among cultured and wild populations of Laminaria japonica. The populations were collected from the coastal area of Dalian, Liaoning Province. The genetic diversity and genetics tructure of the populations were analyzed, and also did the genetic divergence among populations. The purpose is to provide theoretical basis for breeding and protection of idioplasm. Main results shown as follows:Three methods-2×CTAB method, 3×CTAB method and 4×CTAB method were used to extract genomic DNA from sporophyte of Laminaria. The DNA samples of three methods were tested by spectrophotometer and agarose gel electrophoresis. The result was that the first method could be used for extracting genomic DNA from sporophyte of Laminaria, and that was the best ones through which the production had the highest purity.A total of 232 loci generated with 5 primer combinations were obtained from 60 individuals, and 183 were polymorphic loci. On average, 36.6 polymorphic loci were amplified by each combination. For the wild and cultured populations, the percentage of polymorphic loci (P) was 71.98% and 65.95%, the mean heterozygosity (H) was 0.2623 and 0.2277, the Shannon information index (I) was 0.3884 and 0.3426, respectively. It can conclude that the level of genetic variation of wild populations is higher than cultivated population. But there is no significant difference. The genetic diversity among two populations (Ht) is 0.2821, the genetic diversity within population (Hs) is 0.2450 and the gene diversity indexs with populations (Gst) is 0.1314. This shows that most of the variation is from the internal populations. Gene flow is 3.4492, which means there is a certain amount of gene flow among the two populations.Genetic distance (D) of wild population and cultured population was 0.0947, the genetic similarity was 0.9096. The result showed that the two populations were very similar.By analysis of genetic variation and genetic structure of the two populations of Laminaria japonica, we found they all have a higher level of genetic diversity. But compared with the wild populations, breeding population has decreased the diversity of the parameters. Effective measures should be taken to increase the level of heterosis of the cultured population. In this study, AFLP revealed high polymorphism of Laminaria material. Thus, using AFLP to estimate genetic variation and germplasm resources of Laminaria has a certain nature.
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