| White Shrimp(Penaeus Vannamei)is one of the most important economic species in China.The loss of good traits,deterioration of GERMPLASM,diseases and insect pests,and the dependence of parent shrimp on import restrict the development of Penaeus Vannamei culture industry.In order to select the strain with low salt tolerance and adapt to the unique climate conditions in Shanghai,the research group has carried out the breeding work of fine varieties for many years,and has now completed the breeding work of F3 generation.Many families with different genetic characteristics,such as those from Guam,imported families from Hengxing Shrimp Breeding Company in Ecuador,and wild families,have been selected as parents,resulting in a large number of inbred and hybrid families.Therefore,in order to continue the good breeding work,the genetic background of parents,offspring and wild lines should be studied deeply,and the growth and disease resistance of different characters should be evaluated,so all lines should be screened.In this study,13 pairs of microsatellite markers were used to analyze the genetic diversity of 9 cultured populations of Penaeus Vannamei.The allele numbers(NA)of 13 loci were 2-6,and there were 37 Alleles in total,747 Alleles,the polymorphic information content index(PIC)ranged from 0.1292 to 0.6799.Observed heterozygosity obs.Het ranged from 0.2225 to 0.3662,and the mean observed heterozygosity was 0.2915.The Hardy-Weinberg equilibrium genetic index D of Two populations was close to 0,which indicated that the genotype distribution of these two populations was close to equilibrium.The genetic distance ranged from 0.0215 to0.2426,and the genetic distance between Pesquera P29 and Pesquera P15 was 0.2426.The genetic distance between San Alfonso P23 S23 and Pesquera P23 was 0.0215.The mean differentiation index(Fst)of each population was 0.1259,indicating that 12.59%of genetic differentiation came from within the population and 87.41% from within the population.Real-time fluorescence quantitative analysis is widely used in gene spatio-temporal expression difference analysis,inter-population expression difference analysis,probe virus detection and other fields.In this experiment,5 immune-relatedgenes and 2 growth-related genes were selected for gene screening,and 4 populations were compared for growth.The differential expression of TLR1,TLR2,TLR3,Alf and crustin genes in four populations was analyzed by RT-q PCR.The results showed that Tlr1,Tlr2,TLR3 and Alf were the highest in F3 lines from Dayangshan,the expression of Crustin was also relatively high,which indicated that the population might have strong stress resistance.The results of growth comparison among the four populations showed that the relative weight gain rate of j was the highest,and the relative expression of Typsin and ATP synthase genes was also the highest.There was no difference in the relative weight gain between the F3 seedling-raising family j and the Pesquera P15 and the San Alfonsopis P12 populations,but there were differences in the expression of Typsin and TP synthase genes between the two populations.The results of the experiment provided theoretical support for the selection and breeding of high polymorphic and highly differentiated populations with good characters such as disease resistance and growth. |
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