The Preliminary Studies On Genetic Diversity Of Sargassum Thunbergii Along Chinese Coast

Sargassum thunbergii is a familiar type in China seacoast which belongs to phylum Phaephyta, class Cyclospreae, order Fucales, family Sargassaceae,genus Sargassum,Sargassum thunbergii is one kind of warm temperature marine brown alga in the west of North Pacific Ocean,also distributed widely in China seacoast. It is the high quality erbium for the marine animals,such as trepang and abalone. S. thunbergii is an important economic seaweed in China.In this paper,Genetic diversity of four populations along China coast of wild S.thunbergii was conducted using amplified fragment length polymorphism (AFLP) and ITS-2 gene. The four populations were from Lvshun yanchang,Dalian changhai,Shandong haiyang and Zhejiang dongtou. Their genetic diversity provide the basic information on protecting and developing the natural resoures of S.thunbergii. and lay the foundation for the combination of geographic populations cross breeding and improve the level of culture.One hundred and twenty S.thunbergii from four population (thirty individuals per population) were analyzed using five pairs of AFLP primer combinations. AFLP banding patterns were transformed into binary data and matrices were processed by Popgene32 program. Using the data obtained, the genetic diversity and the genetic structure were estimated. Make analysis of four groups and 40 individual species (ten individuals per population) of S.thunbergii and calculate the base content and the genetic distance betwee groups. The experimental results show that measured in the four geographical groups of S.thunbergii part of ITS-2 gene sequence,A,T,G,C content of the average are as follows:21.0%,22.1%,30.1% and 26.8%. No mutation site,there was no base deletion, transversion,and measured exactly the same base sequence.The four populations were the Lvshun yanchang ,Dalian changhai,Shandong haiyang and Zhejiang dongtou. The percentage of polymorphic loci (P) of the four populations was 82.31%,78.97%,91.03% and 94.87%. The mean heterozygosity (H) was 0.2088,0.1862,0.2505 and 0.2736 ; the Shannon information index (I) was 0.3273,0.2974,0.3911 and 0.4236,respectively. The genetic distance was 0.0301～0.1437 among populations.the smallest genetic distance is 0.0301 which between Zhejiang dongtou and Shandong haiyang. the largest genetic distance is 0.1437 which between Zhejiang dongtou and Lvshun yanchang.The Gst coefficient ranged from 0.0182 to 0.0713,The average value of Gst coefficient of the AFLP was 0.0504, indicate genetic variation among groups accounted for 5.04% of total variance, the genetic variation within groups accounted for 94.96% of the total variation, genetic variation within groups is much larger than between groups. The data from Gst demonstrate no significant genetic differentiation between all pairs of populations. most of the variation from the internal groups.The results showed that the genetic diversity of the four populations was poor. AFLP molecular marker technique is highly sensitive to small differences, it is an efficient and reliable a powerful tool for the classification and study of the genetic diversity. Applying to genetic diversity analysis for limited understanding of genetic information and the types with no much difference.