Preliminary Analysis Of The Number Of Sheep Lambing Combined Effects Of Candidate Genes

The litter size of sheep is an important economic character which can determinethe benefit of raising sheep. But the litter size is a kind of low heritability thresholdtrait, the conventional breeding methods genetic improvement progress has been slow.At present, there have many candidate genes been isolated and many molecularmarkers have been identified. And some molecular markers have got effectiveapplication in breeding, while a large number of effect of molecular markers and theinteraction among multiple markers need further researches. In this study, we usedifferent fertility sheep as the research animals.And single nucleotide polymorphisms(SNPs) screening and restrictive length polymorphism (RFLP) were used to analysisthe single-gene effect and polygenic effect of four candidate genes(FecB,BMP15,FSHR,LHβ) which associated with the litter size, also to establish themodels of single gene and polygenetic breeding. The main results are as follows:1. In this study, we collected the litter size records in Doper, Hu Sheep, SmallTail Han Sheep, Doper and Hu Sheep hybridization F1, Merino and Hu sheephybridization F1. The analysis of the litter size trait phenotypic value showed that theaverage litter size was1.737±0.016.These showed that the experimerent groups havemajor variation and have the potential to further improvement in the litter size trait.2. We use general linear model to analysis the single-gene effect of fourcandidate genes (FecB, BMP15, FSHR, LHβ) which associated with the litter size, theresults showed that: the FecB gene, BMP15gene, FSHR gene were significantlycorrelated with the litter size(p<0.05or p<0.01), which can be applied as molecularmarkers to raise the litter size in breeding. The LHβ gene had no significantcorrelation with the litter size.3. We analysis the single-gene effect of four candidate genes which associatedwith the litter size in Small Tail Han Sheep and Hu Sheep, the results showed that:TheFecB gene and FSHR gene were significantly correlated with the litter size(p<0.05orp<0.01) in Small Tail Han Sheep. The BMP15gene and the LHβ gene had nosignificant correlation with the litter size.The FecB gene, the BMP15gene, the LHβ gene were significantly correlated with the litter size(p<0.05or p<0.01) in Hu Sheep.These showed that the candidate genes of different varieties affected the litter sizemight be different.4. We use polygenic merger analysis method and joint effect method to analysisFecB, BMP15, FSHR with single-gene effect significantly or extremely significantly,the results showed that these three genes can influence the litter size together. And thepolygenic effects of genetic markers were consisted with single-gene effect.Theoptimal combination of double genes is FecB-FSHR. The advantage genotype wasBBCC. The optimal combination of three genes is FecB-BMP15-FSHR. Theadvantage genotype was BBG+CC.The above work had certain theoretical and practical reference value for carringout polygenic polymerization breeding with the litter size of sheep.