Studies On Screening Of Microsatellite Markers And Application In Alexandrium

The Alexanderium genus is an important red tide dinoflagellate, widely dispersed around the world, most of which belong to toxicant species. The status of the classification was established based on the morphological characters in the early age. However, large divarications in the status of the genus were always present because of the constantly updated of the morphological classification standards. Microsatellite marker, a developed-rapidly biological technique, has been applied extensively in the field of genetic diversity analysis, genetic map construction, population genetics investigation and so on. In this paper, to provide more information on the molecular identification methods for the genus Alexanderium, some SSR were screened from ESTs database about Alexandrium tamarense by means of bioinformatics, and the genetic diversity was analyzed among 4 strains of A. tamarense, 2 strains of A. affine and 1 strain of A. catenella by capillary electrophoresis. Totally 222 SSR were discovered, one SSR per 18.5 kb in average. The trinucleotide repeats accounting for 48.2%, were dominant among the repeat motifs, of which CTG/CAG was the most type. Twelve of primers were further adopted for the analysis of genetic diversity. Less genetic diversity was observed in intraspecies of Alexandrium spp, with the ratio of polymorphic primers of 41.67% and Nei's gene diversity of 0.2130 in average. In contrast, high genetic diversity was observed in interspecies of Alexandrium spp. with ratio of polymorphic primers of 75% and Nei's gene diversity of 0.4643. The interspecies genetic coefficient of differentiation was higher with the average level of 0.7051. According to the dendrogram of these seven strains, A. tamarense CCMP116 and A. affine CCMP112 greatly closed to each other. A. tamarense ATHK9301, CCMP1598 and ATDH01 clustered together were the same species. A. catenella ACDH01 and A. tamarense distributed in the two branches were different species. These results suggested that the SSR marker was a potentially useful method in the genetic diversity analysis of Alexanderium spp.