| China is one of the richest countries in the world in terms of livestock and poultry genetic resources,and livestock and poultry germplasm resources are the basis for the development of animal husbandry.Yantai Black Pig is native to the eastern part of Jiaodong Peninsula and is one of the excellent local breeds in China.This breed has the characteristics of strong adaptability,superior fertility,excellent meat quality and rough feeding resistance,but also has the problems of slow growth and low meat ratio.With the import of foreign breeds,inbreeding coefficient within the local breed population including Yantai Black pigs increased and the phenomenon of inbreeding decline.In order to strengthen the protection and breeding application of Yantai black pigs,in this study,we analyzed the genetic structure of the Yantai black pig population using the gene chip "Zhongxin-1",tested its disease resistance genes and proposed a method to select individuals with high disease resistance.The results are as follows:(1)The genetic diversity of the Yantai black pig population was analyzed using the Zhongxin-1 gene chip,in which the observed heterozygosity was slightly lower than the expected heterozygosity,and the boar individuals were divided into four families: A,B,C and D.The remaining sow individuals were divided according to their proximity,and it was found that there were uneven relationships and numbers among individuals.In this study,a total of 75 samples of Yantai black pigs were examined for ROH fragments,and the results showed that the largest number of individuals had ROH lengths in the range of 201-300 Mb,with an average ROH length of 391 Mb for this group.Inbreeding coefficients were calculated based on ROH and it was learned that the maximum inbreeding coefficient of this group was 0.45 and the average inbreeding coefficient was 0.16,which is a high degree of inbreeding.(2)Based on the results of IBS genetic distance and PCA analysis,it is roughly inferred that Yantai Black Pigs are more distantly related to Dapulian Pigs and Weihai Black Pigs,while they are more closely related to Zaozhuang Black-capped Pigs.(3)Based on the four disease resistance molecular markers associated with PRRSV and PCV2 identified in the laboratory,individuals of Yantai black pigs were selected for disease resistance by SNP microarray typing technology,retaining those with superior disease resistance genes and screening out those with low disease resistance performance.For example,for the mi R-122 gene,individuals with genotype TT are selected;for the SERPINA1 gene,individuals with genotype GG are selected;for the CYP3A88 gene,individuals with genotype TT are selected;for the USP18 gene,individuals with genotype GG are selected,and genotypes with weak disease resistance are gradually eliminated in the breeding process,with a view to achieving the purpose of disease resistance selection.(4)By means of genetic marker-assisted breeding,the MX1 gene was analysed for polymorphism in 129 samples of Yantai black pigs,genotyped with the help of PCR amplification and combined with the typing results,the individuals with excellent disease resistance were retained.In summary,in this study,we analyzed the genetic diversity,parentage,genetic structure and inbreeding coefficient of the Yantai black pig population and performed a disease resistance gene analysis based on the genes related to disease resistance found in the early stage of the laboratory,which laid a theoretical foundation for the subsequent breeding. |
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