The role of recessive genes in chicken breeding and breed commercialization: genetic basis and prospects for application in Vietnam
Recessive genes represent an important genetic component in chicken breeding, particularly for morphological identification traits, control of hybrid phenotypes and management of breeding lines. This review summarizes the genetic basis of recessive genes in chickens, including their expression in homozygous states, hemizygous expression of sex-linked genes, and the influence of genetic background, gene interaction and environmental conditions. Trait groups with potential applications include plumage colour, feathering rate, sex-linked barring, skin or shank colour, and markers associated with viability and adaptation. Loci such as TYR, K/k+ and CDKN2A/B are relevant for line identification, early sexing and improving phenotypic uniformity in F1 populations, whereas polygenic traits should be considered within integrated breeding programmes rather than through single-marker selection. The review also discusses the roles of phenotypic selection, test crossing, pedigree recording, marker-assisted selection and genomic selection in developing and maintaining base populations carrying recessive alleles. In Vietnam, the application of recessive genes in chicken breeding remains very limited and is largely at a potential stage because of constraints in breeding population size, standardized genetic data and molecular technology capacity. Future research should prioritize the development of integrated pedigree, phenotype and genotype databases, the application of markers for monogenic or oligogenic loci, and the linkage between commercial breeding and sustainable conservation of indigenous chicken genetic resources.
