Genome-wide Association Study And Genomic Selection Of Partial Index Of Growth Performance And Hematology In Yak

Genomic selection is a newly emerging marker-assisted selection breeding technology that covers the genome range.Compared with traditional selection breeding methods based on pedigree information,genomic selection technology can explain more genetic variation that has low heritability.Index with long detection period and high measurement cost can be effectively predicted in advance.Genomic selection technology has been widely validated and applied in important domestic and foreign dairy cattle,beef cattle,sheep and pigs,and has also achieved significant breeding progress.However,there is no relevant prediction and validation work on the yak population.In this study,the Ashidan yak population was used as the research population and 354 18-month-old female yak individuals were used as the experimental reference population,and the yaks’ genome was scanned by using the Illumina Bovine HD778 K commercial chip.Through genome-wide association analysis of hematological index,candidate genes that affect hematological index were screened Four indicators of growth index,withers height,body length,chest girth and body weight and eight indicators of routine blood index(red blood cell count,hemoglobin,blood cell volume,platelet count,lymphocyte count,neutrophil count,platelet distribution width and platelet average volume)is selected as the phenotypic research data,using three statistical methods GBLUP,Bayes B and Bayes Cπ to calculate the genomic estimated breeding value of the reference population and assess the prediction accuracy,which is good for understanding the feasibility and reliability of application of genomic selection technology to the yak population.The main research results are as follows:1.In this study,the genome-wide association analysis method based on high-density chip technology was used to screen the hematological index of Ashidan yak,and 43 significant SNP loci were identified,including 35 potential SNP loci and 8 genome-wide significant SNP loci,which is correlated to 8 of 15 hematological indexes that affect red blood cell count,hemoglobin,Mean corpuscular volume,platelet count,lymphocyte count,Medium white blood cell count,and platelet distribution width.Related genes,namely,GPLD1,EDNRA and APOB,can be used as candidate genes for molecular markers that affect hematological indexes.2.In the population genetic parameter estimation based on genotyping information,the average platelet volume index of Ashidan yak is high heritability(h2>0.6),body length,body weight,withers height,chest girth,red blood cell count,hemoglobin,mean blood cells volume,platelet count,lymphocyte count,mean white blood cell count,and platelet width distribution were medium to high heritability(0.3<h2<0.6).Among them,body length,body weight,withers height and chest girth trait heritability were 0.366,0.508,0.589 and 0.345,respectively;red blood cell count,hemoglobin,hematocrit,platelet count,lymphocyte count,intermediate white blood cell count,platelet width distribution and average platelet volume.The heritability is 0.231,0.373,0.444,0.457,0.464,0.461,0.533 and 0.61,respectively.3.Using 5-fold cross calculation to verify the prediction accuracy,it was found that the prediction accuracy of the 12 target index was different,and most of the index showed moderate prediction accuracy(0.1<r<0.3)in this study.The three statistical methods GBLUP,Bayes B and Bayes Cπ all show approximate predicted trends in 12 target indexes.Among them,the Bayes Cπ method was the most accurate in predicting the genome of lymphocyte counts(r = 0.319),while the GBLUP method was the least accurate in predicting the chest girth index(r = 0.043).Regardless of the method used,indexes such as body weight and hematocrit showed moderate predictive accuracy(0.1<r<0.3).The chest circumference and red blood cell count index showed pretty low prediction accuracy(r<0.1)and could not be used for genomic selection.When using Bayes Cπ method,the prediction accuracy of hemoglobin content and platelet count index was better than that using GBLUP and Bayes B The method improved slightly,reaching a medium level(r>0.1).In addition,Bayes Cπ method shows the best predictive capability on 12 target indexes,so it can be used as the best method for genomic selection in yak population.