A global approach of chicken genetic diversity in Taiwan combining phenotypes and molecular markers

• Main Authors: Chi-Sheng CHANG, 張啟聖
• Other Authors: Yen-Pai LEE
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/47169045301686076642

博士 === 國立中興大學 === 動物科學系所 === 99 === Conservation and utilization for domestic animal genetic resources is a global and important issue for human society. Animal genetic diversity has become eroded during the process of breeding and human selection. Local breeds are potentially useful genetic resources that need to be characterized as the first step of any programme aimed at the conservation of genetic diversity. Molecular tools and phenotypic traits provide information to evaluate the status of population and for conservation program decision-making. This thesis is part of a collaborative programme between Taiwan and France, and is focusing on genetic diversity of six local chicken breeds in Taiwan. The first objective is to use phenotypic data (growth and immune responses) and molecular data (microsatellite markers, mtDNA, MC1R and LEI0258 marker of MHC) to analyze genetic diversity of six chicken breeds conserved in National Chung Hsing University since 1982. A multivariance method is proposed to combine continuous variables (performance traits) and allelic frequencies (molecular data). The combined analysis clearly discriminates all breeds except Ju-Chi and Quemoy which appear very similar except for immune response and MC1R. A selection process has been observed on the MC1R gene which controls variability of plumage colour. The second objective is focusing on chicken MHC polymorphism, as described by the hypervariable LEI0258 marker, and it is effect on immune responses. On a total of 17 LEI0258 alleles, 7 were new. The distribution of MHC genotypes in each breed under a conservation program has been studied for three generations between 2001 and 2008. The results suggest that the polymorphism at the MHC locus can serve as a useful indicator of genetic diversity for monitoring conservation of small populations. A challenge experiment with a low pathogenic avian influenza virus has shown significant differences between breeds, with a faster antibody response in the Quemoy breed and a higher sensitivity to the infection for the Hsin-Yi breed. Breeds also differed in their secondary response to vaccines against Newcastle Disease, Infectious Bronchitis, Infectious Bursal Disease, with most often a higher response in the Quemoy breed. Only four out of nineteen MHC haplotypes were shared between breeds and were found not to influence antibody response. However, a significant MHC effect could be observed within breed, particularly for the Quemoy breed. A refined characterization of MHC alleles found in Quemoy and Hsin-Yi breeds would be interesting. The final conclusion suggest that by combining phenotypic traits and molecular data for evaluating genetic diversity is possible and that MHC locus can be used as a useful indicator for monitoring diversity in relation with disease resistance.