随着大型跨国家禽公司的增长，更少的商业品种的鸡产生了全世界消费的几乎全部鸡肉和鸡蛋。Hans Cheng及其同事证实了品种的减少意味着鸡的遗传多样性的减少。这组科学家比较了标准的禽类品种和来自商业养殖者的品种的数千个称为单核苷酸多样性（SNPs）的遗传标记，结果发现商业鸡群随着时间的推移失去了超过半数遗传多样性。
随着当代鸡的生产变得越来越商业化，家禽业选出了产蛋或产肉能力强的特定品种，形成了商业鸡群的基础。然后养殖者针对每一个品种选出想要的性状从而优化了这些特性，这进一步影响了遗传多样性的程度。这组科学家说，更少数量的公司培育鸡已经进一步减少了鸡的多样性并增大了生存下来的鸡对疾病的易感性。这组作者提出，通过让商业品种的鸡和土鸡杂交繁殖，或者与不同商业鸡群的未灭绝的品种杂交繁殖，可以恢复多样性。相关论文发表在美国《国家科学院院刊》（PNAS）上。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS，doi: 10.1073/pnas.0806569105，William M. Muir， Hans H. Cheng
Genome-wide assessment of worldwide chicken SNP genetic diversity indicates significant absence of rare alleles in commercial breeds
William M. Muira, Gane Ka-Shu Wongb,c, Yong Zhangc, Jun Wangc, Martien A.M. Groenend, Richard P.M.A. Crooijmansd, Hendrik-Jan Megensd, Huanmin Zhange, Ron Okimotof, Addie Vereijkeng, Annemieke Jungeriusg, Gerard A.A. Albersg, Cindy Taylor Lawleyh, Mary E. Delanyi, Sean MacEacherne, and Hans H. Chenge,1
aDepartment of Animal Sciences, Purdue University, West Lafayette, IN 47907;
bUniversity of Alberta, Department of Biological Sciences and Department of Medicine, Edmonton, Alberta T6G 2E9, Canada;
cBeijing Institute of Genomics of Chinese Academy of Sciences, Beijing Genomics Institute, Beijing Proteomics Institute, Beijing 101300, China;
dAnimal Breeding and Genomics Centre, Wageningen University, 6709 PG Wageningen, The Netherlands;
eUnited States Department of Agriculture, Agricultural Research Service, Avian Disease and Oncology Laboratory, East Lansing, MI 48823;
fCobb-Vantress, Inc., Siloam Springs, AR 72761;
gHendrix Genetics, 5831 CK Boxmeer, The Netherlands;
Abstract
Breed utilization, genetic improvement, and industry consolidation are predicted to have major impacts on the genetic composition of commercial chickens. Consequently, the question arises as to whether sufficient genetic diversity remains within industry stocks to address future needs. With the chicken genome sequence and more than 2.8 million single-nucleotide polymorphisms (SNPs), it is now possible to address biodiversity using a previously unattainable metric: missing alleles. To achieve this assessment, 2551 informative SNPs were genotyped on 2580 individuals, including 1440 commercial birds. The proportion of alleles lacking in commercial populations was assessed by (1) estimating the global SNP allele frequency distribution from a hypothetical ancestral population as a reference, then determining the portion of the distribution lost, and then (2) determining the relationship between allele loss and the inbreeding coefficient. The results indicate that 50% or more of the genetic diversity in ancestral breeds is absent in commercial pure lines. The missing genetic diversity resulted from the limited number of incorporated breeds. As such, hypothetically combining stocks within a company could recover only preexisting within-breed variability, but not more rare ancestral alleles. We establish that SNP weights act as sentinels of biodiversity and provide an objective assessment of the strains that are most valuable for preserving genetic diversity. This is the first experimental analysis investigating the extant genetic diversity of virtually an entire agricultural commodity. The methods presented are the first to characterize biodiversity in terms of allelic diversity and to objectively link rate of allele loss with the inbreeding coefficient.
