| China’s chicken production and consumption rank among the top in the world.With the rapid development of large-scale farming,the production of fast-growing broilers(mostly white feathers)has rapidly increased,but the meat quality and taste are far inferior to high-quality yellow-feather broilers.Consumers in the Guangdong and Guangxi provinces pay more attention to meat quality and taste,so they prefer "local chicken" with yellow skin and yellow feathers.Guilin Liyuan Group Nanning Liangfeng Agricultural and Livestock Co.,Ltd.has bred the Liangfeng strain,which is an excellent representative of the local breed in China.At present,the company has two urgent problems that need to be solved: firstly,the yellow color of the skin of the M strain is not enough;secondly,the W strain was bred with fastgrowing white-feather broiler lineage,and carried both recessive and dominant whitefeather genes.Since the use of chickens with dominant white-feather and colored-feather chickens will produce white-feather commercial chickens,the company hopes to clearance of the dominant white feather gene in the white feather line.The purpose of this study is to develop a molecular identification method that can quickly identify the yellow skin phenotype and the dominant white feather locus genotype in chickens,and use them to quickly improve the yellow skin phenotype of the line and eliminate the dominant white feather gene in the population.Based on the mutations in the chicken yellow-skinned gene(BCO2)and the dominant white-feathered gene(PMEL17),a molecular identification method for the chicken yellow skin phenotype and dominant white feather locus genotype was developed.And the two methods were tested to be accurate and reliable.The main results obtained from the study are as follows:(1)Development and application of a molecular identification method for chicken yellow skin phenotype.The experimental protocol was designed from five mutant loci in the BCO2,which has been reported to control the color of yellow and white skin in chickens,and finally a four-base deletion(W locus)in the fourth intron of the gene was selected to establish the identification method.Select 50 chickens from two flocks with yellow skin and white skin that can accurately judge skin color,and collect blood from wing veins to extract genomic DNA.Molecular markers were used to detect the W locus of the M strain population,and the molecular identification method of chicken yellow skin phenotype was100% accurate through the control test.This method is low-cost and high-efficiency,and the detection cost of each chicken is only about 5.0 yuan.Molecular identification was carried out on more than 3,500 chickens of the M strain,all of which were yellow-skinned chickens;molecular identification was carried out on 1,500 chickens of the Q strain,and1,042 chickens were white skin and 458 chickens were yellow skin.(2)Development and application of molecular identification methods for chicken dominant white feather locus genotype.The identification method was established by using the insertion of 9 bases in the tenth exon of PMEL17(I locus).114 male chickens were randomly selected in the W strain for validation,blood was collected from wing veins,genomic DNA was extracted,and the results of the I locus mutation in the W strain population were examined.Meanwhile,the population of roosters was crossed with a population of hens(genotype ii)that did not carry the dominant white feather gene.The results of molecular identification were consistent with the test results of dominant white homozygous(II),dominant white heterozygous(Ii)and dominant white recessive(ii)individuals up to 96%,96.78% and 100%,respectively.The method is low-cost and highefficiency,and the cost of testing is only about 10.0 RMB per chicken,which is one-third of the market price.(3)The dominant white feather gene detection was carried out on the W strain population,and the number of dominant white homozygous(II),dominant white heterozygous(Ii),and dominant white recessive(ii)individuals were 1731,1554,and 125,respectively.The genotype frequencies of II,Ii,and ii are 50.76%,45.58%,and 3.67%,respectively.The gene frequency of the dominant white feather allele(I)is as high as73.55%,and the gene frequency of the colored feather allele(i)is only 26.45%.To completely eliminate the dominant white feather allele(I),it is necessary to select individuals with genotypes Ii and ii to multiply,increase the frequency of the i allele,and then perform another screening.(4)In order to improve the speed and efficiency of genotype molecular identification,the fast extraction method of chicken blood genomic DNA using chelated ion exchange resin developed by our group was optimized for the template extraction method used in PCR,which greatly improved the efficiency of PCR amplification.(5)In the offspring generation of the W strain,the population not carrying the dominant white feather gene was marked as A and the population carrying the dominant white feather gene was marked as B.It was found that the dominant white feather gene I had no significant effect(P >0.05)on the population’s body weight,death rate,fertilization rate,live embryo rate,healthy chick rate,green chick rate,dead semen rate,second chick rate,residual chick rate,hatching rate of incubated eggs and green chick rate of live embryo eggs,but it significantly affected the rate of fetal eggs,hatching rate of fertilized eggs,and hatching rate of live embryo eggs were not significantly affected(P <0.05).In summary,this study developed a molecular identification method for chicken yellow skin phenotype and a molecular identification method for chicken dominant white feather locus genotype.The two methods are cost-effective,accurate,efficient,easy to use,and meet the actual production needs.Using the molecular identification method of chicken dominant white feather locus genotype,it was found that the carrier of the dominant white feather gene in the progeny population of Liangfeng chicken W strain would significantly affect the fetal egg rate and hatchability at hatching. |
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