Japanese Silkie Fowls are Widely Distributed in the Phylogenetic Tree Derived from Mitochondrial Complete D-loop Nucleotide Sequences

Abstract

The Silkie fowl (Gallus gallus var. domesticus) is distinct from other chicken breeds in terms of its appearance and behavioural characteristics. It is a Japanese native breed and has inhabited Japan since before the Edo era. Although the breed is considered to have originated in India and established in China and Japan, its evolutionary history and genetic relationship with other breeds are not clear. In this study, we determined the mitochondrial complete D-loop nucleotide sequences of 27 Silkie fowls and 3 other chicken breeds. In the Silkie fowls, we found 27 sites of single nucleotide polymorphism and 4 sites of single nucleotide insertion. Phylogenetic analysis revealed that the Silkie fowls, 9 other chicken breeds, 4 red jungle fowls and 42 haplotypes in Oka et al. (2007) were distributed in 5 clades. Silkie fowls belonged to 5 clades (A-E). These results suggest that Japanese Silkie fowls have high genetic divergence. However, all categories except SLSG (Saga Prefectural Livestock Experiment Station, white feathers) were distributed in only 1 or 2 clades, and 5 individuals with black feathers belonged to clade A. The Silkie fowl's wide distribution in the phylogenetic tree suggests that old Asian breeds crossed with several chicken breeds that had unusual traits to establish the Silkie fowl breed.