International Journal of Molecular Zoology, 2025, Vol.15, No.1, 20-28 http://animalscipublisher.com/index.php/ijmz 21 some local varieties in China, one can also see colors that fall between the two, or new types of feather colors. The Wugangtong goose is a typical example. Its feathers are either grey or white, and its chest is also white, presenting a unique pattern of "grey base and white chest" (Banerjee, 2013; Feng et al., 2022; Yang et al., 2024). Some geese also show cinnamon-colored feathers, which may gradually change from all white to all cinnamon. Some geese also have variations in the color of their beaks and irises. Their tibial colors are relatively uniform. Adult geese are generally orange, while goslings are yellow (Gladbach et al., 2010; Hamadani and Khan, 2016; Martsev, 2020). 2.2 Geographical and breed-specific distribution Grey feathers were the most common feature of wild ancestors, and some domestic goose breeds still retain this color to this day. White-feathered geese are more commonly found in domesticated geese, especially in breeds from China and Europe (Devrim et al., 2007; Xi et al., 2020; Wen et al., 2021). Some color changes are also related to specific gene mutations. A 14-base insertion mutation in the EDNRB2 gene was found in Chinese geese. This variation did not occur in European goose breeds, indicating significant genetic differences between China and Europe (Xi et al., 2020; Gao et al., 2023). The local breed of Wugangtong goose in China is very representative. It can be classified into different phenotypes such as gray feathers, white feathers and white breasts. Terrill and Shultz (2023) and Yang et al. (2024) believe that this indicates that the diversity of feather colors may be closely related to artificial breeding and local environmental adaptation (Figure 1). Ouyang et al. (2022) and Wen et al. (2023) discovered that the Huoyan goose from Northern China shows some special feather colors, which is closely related to its environment and species history. Figure 1 Plumage variations in offspring of grey WGT geese (Adopted from Yang et al., 2024) Image caption: Goslings in (A) show three different plumage variations, and these variation types (1, 2, and 3) were destined to be those in (B) when they grew up. The eye color of types 1, 2, and 3 plumages was brown, brown, and blue, respectively (Adopted from Yang et al., 2024) 2.3 Heritability and observed inheritance modes The feather color of domestic geese is mostly determined by genetics and has relatively high heritability. Their genetic patterns generally conform to Mendelian’s laws of inheritance and are manifested as dominant or recessive (Cheng et al., 2003; Yu et al., 2019). Xi et al. (2020) found that there was a 14-base insertion mutation in the EDNRB2 gene, which was recessive for white-feathered geese, indicating that white-feathered geese are homozygous, while most grey-feathered geese are heterozygous. Yang et al. (2024) demonstrated that in Wugangtong geese, gray feathers and white feathers show codominance, while the appearance of white breasts is related to the heterozygous state of this gene. Wen et al. (2023) believe that feather color may also be related to gender. In Huoyan geese, the feather color of gosling is associated with the Z chromosome and is influenced by the TYRP1 gene. Xu et al. (2022) demonstrated that there are also differences between male and female geese in terms of melanin content and the expression of related genes. In Holdobaggy geese, the feathers on the backs of female geese are darker in color because they have higher melanin content and TYRP1 expression.
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