Construction Of High-density Genetic Linkage Map,growth Related QTL Mapping And Parentage Determination Of Sander Lucioperca

The pikeperch(Sander lucioperca)is one of the most economically important freshwater species.However,in pond culture,most pikeperch individuals must be cultivated for nearly 2 years to reach harvestable size(>0.75 kg).In this study,SLAF-seq(Specific-Locus Amplied Fragments could Sequencing)technology was used to develop SLAF markers,and to construct the high density genetic linkage map of pikeperch,The quantitative trait loci(QTLs)for growth related traits were also detected.SNP markers in QTLs were screened and used to do correlation analysis with growth traits of pikeperch.Based on 34 SNPs,25 pairs of pikeperch and their 598 offsprings were used for parentage determination,and the fast growing families were screened out according to the growth performance of their offspring.These studies surely provide basic knowledge for genetic management of breeding stocks and marker-assisted selective breeding of pikeperch.1 Construction of the high-density genetic linkage map of pikeperch(Sander lucioperca)using SLAF-seqSLAF-seq was performed on 2 pikeperch parents and their 150 offspring(FI generation).In total,436.58 M reads were acquired,with average sequencing depths of 100.16-fold for the parents and 19.51-fold for each FI offspring.A total of 237,687 high-quality SLAFs were detected,34,774(14.63%)of which were polymorphic.19,147 SLAFs with five segregation patterns(ab × cd,ef × eg,hk × hk,lm × 11,and nn× np)were used for genetic map construction,accounting for a ratio of 8.06%,After filtering,a total of 8,275 loci were used for initial linkage map construction.The final merged linkage map consisted of 8,159 SLAFs in 24 linkage groups(LGs)and spanned 3,421.81 cM,with an average inter-marker distance of 0.46 cM.The largest LG was LG10,which contained 313 markers with a length of 201.20 cM;the smallest was LG15,which only contained 70 markers that spanned 83.74 cM.The maternal map contained 5,239 SLAFs with a total genetic distance of 2,582.83 cM,and the corresponding paternal map consisted of 4,221 SLAFs,which spanned 4,179.41 cM.The linkage map should be useful for improving pikeperch marker-assisted selection in the future.2 Phenotypic data statistics of mapping population and QTL analysis of growth-related traits of pikeperch(Sander lucioperca)Based on this high-density genetic linkage map,21 QTLs were identified for eight growth-related traits including total length,body weight,body length,head length,body height,body thickness,body girth and slaughter weight.Three QTLs for each trait,including slaughter weight,body girth,body weight,and body thickness,were detected on LG6 or LG 16.Moreover,five QTLs for body length were detected on LG6,LG9,and LG 18.QTLs for total length,body height,and head length were detected on LG6.In the 21 growth related QTLs,32 SLAFs were dected in the QTL of body length,which is the QTL with the most tags.There are only 2 SLAFs in the QTL related to total length and head length,which is the QTL with the least number of tags.QTLs related to body weight,body thickness and slaughter weight were mainly concentrated on LG 16,and these 7 QTLs had an overlap region(42.37-43.041cm).While QTL regions for all traits except body girth overlapped on LG6 from 62.851-63.46 cM.3 Screening of SNP in QTLs and their correlation analysis with growth of pikeperch(Sander lucioperca)In order to find SNP markers significantly related to growth traits,primers were designed for 41 SNP molecular markers in the growth related QTL of pikeperch,and preliminary verification and analysis were carried out in the mapping population of parent genome.The results showed that 20 locus were amplified to specific bands and successfully genotyped in the parents base on the KASP(Kompetitive Allele-Specific PCR)genotyping technology.20 SNPs were used to scan the randomly mixed population(n=298)of pikeperch,and a total of 19 SNPs showed polymorphism in this population.The correlation analysis of growth traits showed that M153213,M78531,M23410 and M71805 were significantly correlated with the growth traits(P<0.05),and M35696 was highly significantly correlated with the growth of pikepcreh(P<0.01).4 Pedigree determination and selection of excellent families of pikeperch(Sander lucioperca)based on SNP genotyping34 SNP was used to identify 25 pairs of pikeperch parents and their 598 offsprings based on the KASP genotyping technology and self-developed software,and the fast growing families were selected according to the phenotype data of their offspring.The results showed that KASP can realize the genotyping of large-scale samples,and 538 offsprings were successfully pedigree determined,and the rate of identification was 89.97%.According to the growth traits of their offsprings,F4,F6,F7,F9,F10,F11,F25 and F30 were selected as the excellent eight families and their growth rates were extremely significant or significantly faster than that of slow-growing families(F5,F12,F16,F19,F23,F24,F27 and F28).The family F9 possessed the maximam dominant genotypes(21 dominant genotypes).In addition,the average number of dominant genotypes of the fast growing families was 17.22,significantly higher than that of the slow growing families(8.5).There was no significant difference in the genetic diversity between parent population and their offspring population,indicating that the decrease of genetic diversity could be effectively prevented when the effective breeding population was kept at 50.The analysis of the kinship among the families showed that family F18 were one branch alone,and the other 24 families were aggregated into one branch.The above results would be helpful for genetic selection of pikeperch in the future.