| In order to explore the degree of genetic diversity and provide a genetic improvement of Marsupenaeus japonicus, AFLP and SSR techniques were applied to investigate genetic diversity in four wild populations, which were collected from Xiamen, Fujian (XM); Zhanjiang, Guangdong (ZJ); Beihai, Guangxi (BH); Haikou, Hainan (HN). The main results are as follows:1. 10 pairs of AFLP and SSR primers were selected for study of genetic structure of Marsupenaeus japonicus. 196 loci were amplified using 10 pairs of primers combinations by AFLP marker, and 102 of which were polymorphic, and the proportion of polymorphic was 52.04 %. As for SSR marker, 42 alleles were amplified using 10 pairs of primers. On average, 4.2 alleles were amplified by one pair of primers. Results gained respectively by AFLP and SSR methods showed high polymorphism in all 4 populations. The level of genetic variation calculated by SSR marker was obviously higher than that of AFLP marker. The effective alleles number (Ne) of SSR and AFLP were 1.2734 (AFLP) and 3.087 (SSR) respectively, heterozygosity ranged from 0.1649 to 0.1788 across populations for AFLP, observed heterozygosity and expected heterozygosity for SSR ranged from 0.4492 to 0.6243 and 0.5275 to 0.7193 respectively.2. Effective alleles number (Ne), Shannon's indexes and other genetic parameters calculated by SSR marker were obviously higher than that of AFLP marker. Although there were some distinctness between the results gained by two methods, the highest level of genetic diversity was XM population both in two methods. Moreover, the clustering analysis in two methods were same, that was 4 different geographic populations were divided into two groups, ZJ and HN populations clustered into one group, then clustered with XM population. Finally, the 3 populations above clustered together with the BH population, which had the farthest genetic distance with the above 3 populations. This trend was accord with the geographical location of 4 populations.3. Genetic diversity indexes in 4 populations calculated by AFLP and SSR methods all showed that high genetic diversity existed in all Marsupenaeus japonicus samples, and genetic variation of different populations existed geographically. The results also indicated a certain extent differentiation among 4 populations. Therefore, in the fishery production, we should establish a series of reasonable management measures to maintain the level of variation in Marsupenaeus japonicus as far as possible, maintain variation of natural fertility and sustainable development and exploitation of biological resources. |
