| Genome-wide selection signal detection can be used to rapidly screen candidate sites for population traits,providing guidance for molecular marker-assisted breeding.The East Friesian sheep are world-famous dairy sheep,with high fecundity and good lactation performance.In recent years,Northwest A&F University Jinchang Meat Sheep Experimental Demonstration Base and other enterprises use the East Friesian raws to carry out the breeding of new varieties of meat and milk sheep,excavating the molecular markers of lactation and reproductive traits of East Friesian sheep which can provide important technical support for the breeding of new varieties of dairy sheep and germplasm resource innovation in China.In this study,the whole genome resequencing was performed on 30 East Friesian stud rams.Combined with the published data of 153 sheep(10 Suffolk sheep,10 Chinese Merino sheep,10 Gothland sheep,Hu sheep 29,German Merino sheep,42 Altay sheep and 30 Tibetan sheep),the genetic diversity of the East Friesian sheep population was explored,the genome selection signals of the East Friesian sheep were detected,and the molecular markers related to the lactation traits of the East Friesian sheep were screened.The findings are as follows:(1).By the analysis of population genetic components,it was found that genetic differentiation happened within the East Friesian sheep.By the estimation of nucleotide diversity in the East Friesian sheep,Suffolk sheep,Chinese Merino sheep,Gotland sheep and Hu sheep,it was found that the nucleotide diversity of East Friesian sheep was the lowest,while the nucleotide diversity of Hu sheep was the highest,indicating that the East Friesian sheep may have undergone a stronger breeding process.(2).By genome-wide signal selection analysis,a 4 Mb haplotype in the East Friesian sheep with a known milk protein rate trait QTL of sheep was identified,indicating that this region may be related to the lactation performance of the East Friesian sheep.In addition,the genes COL3A1 and COL5A2 associated with lactation traits were found based on the selection signal,and a missense mutation was identified in the COL3A1 gene.(3).62 SNPs related to lactation were screened out in the East Friesian sheep,and a set of molecular markers that can be used for lactation performance selection of crossed offspring of the East Friesian sheep and Hu sheep was provided,which can be used for the selection and matching of dairy sheep in Jinchang base.(4).The three major genes about high fecundity in sheep,GDF9,BMP15 and BMPR1 B,were not found to have coding region mutations and no selection signals about fecundity were found in the East Friesian sheep,indicating that the fertility of sheep is a complex trait,and the genetic mechanism of the high reproductive trait of the East Friesian sheep has yet to be studied.In summary,based on the whole genome resequencing data of 183 sheep,this study identified the genes and haplotypes related to the lactation traits of the East Friesian sheep,and provided a set of molecular markers related to lactation performance,laying theoretical foundation for building QTL positioning for subsequent single nucleotide polymorphism(SNP)markers and finding the correlation between milk production and abortion rate.Also,this study explored new breeding methods for dairy sheep,and provided technical support for the selection and matching of dairy sheep in Jinchang base. |
