The Genetic Analysis Of Breast Muscle Fiber And Meat Color Traits Of Duck

In 2019,4.43 billion ducks were bred in China,ranking first in the world.Duck meat was the thirdlargest meat consumer product after pork and chicken.At present,Chinese consumer required for food has changed from quantity to quality,and the demand for meat quality of animal products is getting higher,the market needs huge High-quality meats.The breeding of high-quality meat duck is a major industry direction.Skeletal muscle is the most important component of the animal body,accounting for 40%-50% of body weight and muscle fiber is the main component of skeletal muscle that was closely related to the meat yield and quality.Exploring the genetic basis of duck breast muscle fiber and meat color traits will provide a theoretical basis for the selection of high-quality meat duck.In this study,based on the mallard × Peking duck F2 resource population,Pekin duck,mallard breast muscle fiber data and meat color data,combined with whole genome re-sequencing data,Genome-wide association analysis(GWAS)was used to identify candidate genes and possible causal variations that affect breast muscle fiber and meat color traits.In order to calculate genetic parameters of breast muscle fiber and meat color traits.In this study,we collected 3 muscular histological phenotypes(fiber area,fiber diameter,fiber density)of 479 ducks from an F2 segregating population generated by mallard × Pekin duck crosses and 10 Pekin ducks and 10 mallards.The results showed that the fiber diameter and area of Peking duck were larger than the mallard and F2 population(P < 0.05).In fiber density,Pekin duck was lower than the mallard and F2 population.At the same time,we also collected the thickness of perimysial and endometrium of 479 ducks from an F2 segregating population generated by mallard × Pekin duck crosses.In the F2 population,the thickness of perimysial is 21.65 ± 5.74 ?m,and endometrium is 4.61 ± 1.38 ?m.In meat color traits,we collected three meat color phenotypes(including redness a*,yellowness b*,and brightness L*)in 555 ducks from an F2 segregating population generated by mallard × Pekin duck crosses.We estimated the heritability of these traits.The results showed that the estimated heritability of fiber diameter and area displayed a moderate heritability at 0.32,and the estimated heritability for fiber density,the thickness of perimysial and endometrium,muscle brightness L *,redness a * and yellowness b * displayed a low heritability which was 0.20,0.17,0.19,0.23,0.12,0.13,respectively.Subsequently,phenotypic and genetic correlation analysis among these traits mirrored one another.The strong correlation was observed between fiber diameter,fiber area and fiber density(r > 0.5),and weak correlation between fiber diameter,the thickness of perimysial and endometrium,muscle brightness L *,redness a * and yellowness b *(-0.3 < r <0.3).We performed a GWAS based on the mallard × Peking duck F2 resource population muscle fiber traits and identified a quantitative trait locus(QTL)significantly associated with muscle fiber diameter on chromosome 3(11.16Mbp-11.40Mbp)contained 3 annotated genes(NDUFAD1,ESF1,TASP1).Then,we discovered the selection signatures using the fixation index and ?? among 40 mallards and 30 Pekin ducks in this QTL region,we calculated the Fst(fixation index)value of each SNP site between the Pekin duck population and mallard population,identified high fixation of 22 SNPs(Fst > 0.7),and the Pekin duck population showed lower nucleotide diversity(? = 2.3 × 10-4)than the mallard population in the QTL region.Furthermore,we characterized the recombination event in this QTL region and identified a 6-kb block(11,390,000bp-11,397,000bp)located on TASP1 that was significantly associated with muscle fiber diameter.Finally,five SNPs were screened as potential causative mutations within the 6-kb block.We performed a GWAS based on the mallard × Peking duck F2 resource population meat color traits and found a potential significant SNP association with muscle yellowness(-log10 P = 8.28).Then,we examined the loci of interest more closely by calculating pairwise linkage disequilibrium(LD).42 SNPs spanning a region from 0.37 Mbp to 0.43 Mbp on chromosome 9 where contained 7 annotated genes were highly correlated(pairwise r2 >0.4).We found the m RNA expression of five genes were expressed in breast muscle.Then we conducted gene functional annotation for these genes.Finally,SELENOT was identified as candidate gene for meat color b*.