MICROSATELLITE ANALYSIS ON GENETIC DIVERSITY OF BREEDING POPULATIONS AND WILD POPULATIONS OF CRASSOSTREA GIGAS
To study the genetic diversity and genetic structure of three breeding populations(LY2-K7,LY2-K11,LY2-K4)and six wild populations(QHD,LS,HD,ZH,WD,KTD)of Crassostrea gigas,genetic analysis was performed on 269 individuals from 9 populations of C.gigas by using 21 polymorphic pairs of microsatellite primers.The results showed that 460 alleles were detected in 21 microsatellite loci,and the mean number of alleles was 21.905;the polymorphism information content(PIC)of 21 microsatellite loci was all greater than 0.5,indicating high genetic polymorphism;the genetic diversity of breeding population LY2-K11 was the lowest(Na=13,I=2.128,He=0.831,PIC=0.825),and that of wild population KTD was the highest(Na=29,I=3.112,He=0.941,PIC=0.938);66％of 189 population locus combinations deviated from Hardy-Weinberg equilibrium,indicating heterozygote loss in these populations;the genetic differentiation coefficient(Fst)of the 9 populations ranged from 0.012 to 0.064,indicating that the genetic differentiation level was low among the populations;AMOVA analysis showed that the genetic variation was mainly from within the individual;the results of PCoA analysis were consistent with UPGMA phylogenetic tree,LY2-K11 population was grouped into one category,the QHD and HD populations into one category,and the other 6 populations into one category.In summary,the breeding and wild populations all have the highly genetic diversity,and the diversity of LY2-K11 population decreased slightly after breeding.In the process of breeding,the quantity and quality of parents should be ensured to prevent the decrease of genetic diversity and the deterioration of seed stress resistance from inbreeding depression.The results will provide scientific guidance for the breeding of new varieties and the protection of wild germplasm resources of C.gigas.
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