The Maternal Origins And Genetic Diversity Of Six Indigenous Chicken Breeds In China

To uncover the relationships, origins and divergence of livestock and poultry breeds, and decide the diversity status of each breed are very important for the protection and utilization of indigenous breeds. In this study, the maternal origin and genetic diversity of six indigenous chicken breeds of China were investigated by analyzing the partial D-loop region of chicken mitochondrial DNA (mtDNA). The results are as follows:Through sequence alignment and constructing neighbour joining(NJ)and MP unrooted phylogenetic trees, we found that, of the six chicken breeds, Wenchang, Luxi game, Shouguang, Jining Bairi and Laiwu Black have five, five, five, six and seven haplotypes, respectively; whereas Langya breed has only three haplotypes. Six Chinese indigenous chicken breeds were clustered in three clades, of which clade A is dominant. Clade A includes 17 haplotypes which are shared by ten Shouguang, nine Luxi game, five Wenchang, six Laiwu Black, six Jining Bairi and two Langya individuals, accounting for 100%, 90%, 84%, 75%, 60% and 20% of the total number of each breed, respectively. These indigenous chickens have close relationship with the G .g .gallus, G. g. jabouile, G. g. spadiceus distributed in Laos and Yunnan Province of China. Clade B contained eight Langya (80%) and one Jining Bairi individuals(10%). Clade C contained one Luxi game (10%), one Wenchang (16.7%), two Laiwu Black (25%) and three Jining Bairi individuals(30%). Domestic chickens of Clade B and C were clustered with H19 and H32, H33 of G. g. gallus. The cluster result indicated that the sixChinese indigenous chicken breeds may be originated from the continental subspecies of Gallus gallus of Yunnan, Laos and Vietnam or its surrounding areas. Mismatch distribution and Fu's Fs test suggested that the five Shandong indigenous chicken breeds did not undergo population expansion in the past. Twenty-nine polymorphic sites of transition, transversion, however, no insertion/ deletion, and 20 haplotypes were found in the above 54 individuals of Chinese domestic chickens. The nucleotide diversity of the chicken is 5.53% according to the 524bp fragment. Intrapopulation nucleotide and haplotype diversity studies indicated that average number of nucleotide differences (K=7), haplotype diversity (H=0.9643) and nucleotide diversity (Pi=0.0134 ) of Laiwu Black chickens were highest, the Pi and K value of Luxi game and the H value of Langya chicken were the lowest.Interpopulation nucleotide divergence and net nucleotide divergence were 0.953% to 1. 801% and -0.134% to 1.17%, respectively. Analysis of molecular variance indicated the genetic differentiation among the different strains was not significant. Gene flow is the major factor affecting genetic diversity of chicken breeds.The results indicated that the six indigenous chicken breeds of Wenchang, Luxi game, Shouguang, Jining Bairi, Langya and Laiwu Black were from the continental subspecies of Gallus gallus of Yunnan, Laos and Vietnam or its surrounding areas, the five Shandong indigenous chicken breeds did not undergo population expansion in the past, the genetic differentiation among the different strains was not significant and gene flow is the major factor affecting genetic diversity of chicken breeds.The maternal origin and genetic diversity revealed by present study will be useful for the protection of indigenous chicken breeds, chicken breeding that use indigenous breeds as breeding materials and chicken production of high quality.