| Duck farming is an important part of China’s modern agricultural production system.And China has become the world’s largest country engaged in duck production,consumption,and export trade.The industry chain for ducks encompasses various stages such as breeding,hatching,feather and processing,slaughter,sales of ducklings,and other related links.It has been proven that eggshell quality,including factors like eggshell weight,egg shape index,and shell thickness,can have a significant impact on both the breakage rate of eggs during transportation and the quality of ducklings that hatch from them.Eggshell quality traits are primarily affected by both genetic and environmental factors,with moderate or low levels of heritability.It is practically important to improve breeding programs to study the underlying genetic basis of duck egg quality.Tianfu Nonghua-G strain,as a specialized parent matriline,has the benefits of a faster growth rate and greater reproductive efficiency.There is currently a high proportion of breeding for its growth performance and indicators of feather color.Moreover,there is a need to strengthen the reproduction of its eggshell quality to improve its market share.Thus,by taking ducks(Tianfu Nonghua-G strain)as the primary object of investigation,this study measured egg quality traits at the age of 170 and 270 days of duck.The related results of molecular markers and candidate genes screened by GWAS and transcriptome analysis are as follows:(1)The analysis of egg quality variation in the age of 170 and 270 days of duck populations showed that there were large coefficients of variation in shell strength,yolk color,and albumen height at the age of 170 days of age,which were 20.24%,21.44%,and 22.47%,respectively.The coefficients of variation for yolk color and albumen height at 270 days of age were also large,with 22.34% and 29.42% respectively.(2)This study compared differences in eggshell and internal egg quality traits at the age of 170 and 270 days of duck.Compared with those at the age of 170 days of duck,the eggshell quality traits such as egg weight,shell weight,and eggshell thickness,and the internal quality traits such as yolk ratio and albumen height were significantly higher at the age of 270 days of duck(P < 0.01).However,the egg shape index and albumen ratio were significantly reduced(P < 0.01).(3)Based on GWAS analysis,291 and 161 SNPs were identified to be significantly associated with eggshell and internal egg quality traits,respectively.152 and 89 potential candidate genes were annotated to be significantly associated with eggshell and internal egg quality traits,respectively.The KEGG enrichment analysis was conducted and revealed that the calcium signaling pathway,MAPK signaling pathway,and vascular smooth muscle contraction pathways were associated with eggshell weight and shell thickness.Pathways such as the ErbB signaling pathway and phosphatidyl inositol signaling system were associated with yolk weight and albumen height.Some key candidate genes were identified by GWAS screening,such as CACNA1H and CACNG3 genes related to eggshell weight,CACNA1C and ITPR1 genes related to eggshell thickness,ERBB4 and PRKCB genes associated with yolk weight,GPR20 gene associated with Hastelloy unit.(4)Screening for extreme differential individuals based on eggshell weight traits and transcriptome sequencing analysis.A total of 837 differentially expressed genes(DEGs)were screened.Functional enrichment of DEGs showed that multiple pathways related to calcium ion transport across the membrane were activated in the oviductal shell gland of ducks in the high and low eggshell quality groups.The intersection analysis of all DEGs screened by transcriptome and candidate genes screened by GWAS was carried out.There were three candidate genes were screened associated with eggshell quality traits,including SEL1L3(egg weight),MMP16(egg shape),and TBXAS1(eggshell thickness).In this study,some key candidate genes related to duck egg quality by GWAS and transcriptome were screened,indicating that related to calcium ion transport during egg formation.The above results provide primary data for molecular breeding for the quality of Tianfu Nonghua Ma duck eggs. |
