Based On The Pedigree Reconstruction Of The Conservation Breeding Population Of Maiwa Yak In Sichuan Longri Breeding Farm By GBS

Maiwa yak is an excellent yak breeds in Aba area of northwest Sichuan.It belongs to plateau grassland yak which included in the ’China Cattle Variety Record’ and’Sichuan livestock and poultry Variety Record’.In this study,406 Maiwa yaks were selected from three breeding groups(Fenzui,Quanhei and Fuluo)in Longri Breeding Farm.The genetic status of Maiwa yak was investigated by genotyping-by-sequencing(GBS),and then the breeding effect was evaluated.We also determine the genetic relationship and reconstructed the pedigree of the whole population.The main research results are as follows :1.GBS sequencing and quality control of 406 yak blood genomes were carried out.The effective base number was 279.21~2456.34 Mb,and the original data was 327.517 Gb,with an average of 806.69 Mb.The base detection error rate was 0.04%~0.06%;The sequencing depth was 5.65 ×~31.64 ×.SNP detection was performed on the sequencing valid data,and a total of 1628805 SNP loci were identified.A total of 126122 high-quality SNP loci were obtained,and 2423 genome sequences contained more than 10 SNPs,accounting for 59.9% of the total sequencing sequences.2.Ho and He of the three breeding groups were 0.3029~0.3044 and 0.3025~0.3052,there was no significant difference between them.Combined the results from LD attenuation,the three breeding groups were in a state of genetic balance,and were less affected by other breeds.The overall genetic variation was consistent among all three groups.The FST of the Fenzui and Quanhei groups was the largest,which was 0.03513,and the FST of Fuluo and Quanhei groups was the smallest,which was 0.02504.Combined with PCA analysis,it was shown that Fenzui group and Quanhei group had an obvious differentiation trend,and the breeding effect was good.The Fuluo group was closely clustered with the Fenzui and Quanhei groups,which might be derived from the parent hybridization of the Fenzui and Quanhei groups.3.In this study,164836 relationship coefficient pairs were calculated.According to the relationship coefficient between individuals,134 full-sib relationships,912 halfsib relationships,136 suspected parent-child relationships or full-sib relationships,520 suspected half-sib relationships or uncle-nephew relationships,205 suspected half-sib relationships or uncle-nephew relationships or the grandparent-grandchild relationships were determined.Combined with the phylogenetic tree and genetic relationship,the whole group was divided into 12 families and the G1 pedigree was reconstructed.The analysis of genetic diversity among 12 families showed that Ho = 0.2889~0.3055,He= 0.3074~0.3076,Ho was lower than He,indicating that there was a certain degree of inbreeding in 12 families.G8 has a minimum Ho of 0.2889 and a maximum FIS of0.0607.Considering the degree of inbreeding and individual number,G5,G6,G8 and G11 families may have adverse effects on subsequent breeding work.Therefore,these families should be strictly controlled in the process of open population subculture and breeding,and excellent bulls should be selected for breeding and conservation.This study explored the application effect of GBS technology in Maiwa yak from the perspective of Molecular Genetics and Population Genetics.The conservation and breeding effects of Longri Breeding Farm were evaluated.Optimized the pedigree information of the whole group,also verified the effect of family building.It provides essential work for subsequent conservation and breeding of Maiwa yak.