1. INTRODUCTION
Since the 1980s, the Chinese beef industry has expanded considerably and
this progress has been accompanied by the introduction of several foreign specialized
beef breeds, especially from Europe. European breeds are often used as
sire lines for crossbreeding with Chinese indigenous cattle breeds. Such breeding
schemes have contributed in improving individual weight gain and beef
carcass weight of Chinese breeds [27], which only account for two-thirds of
the world average level and about one half of that in developed countries, such
as Canada, Australia, and USA. However, such crossbreeding with foreign
breeds also results in consistent and rapid loss of genetic diversity by dilution of
the autochthonous genetic makeup.
The existence of genetic polymorphism or diversity in a population is the
basis of genetic improvement by selection and needs to be accurately estimated
[23]. In the past decades, animal genetic diversity has been assessed according to
various criteria including phenotypic, biochemical, and molecular parameters.
With the development of molecular biology techniques, nucleotide variations
in DNA sequences can be detected directly such as microsatellite markers identified
in all eukaryotic species investigated so far [3,18]. Microsatellite markers
have become the mainstay of genetic linkage mapping and quantitative trait loci
identification for economic traits and they have also been used to address questions
concerning the genetic diversity and the genetic relationships in species
such as cattle [11]. However, in cattle, most of these studies have focused on
European breeds and little information is available on the genetic diversity of
Chinese indigenous cattle breeds. The purpose of the present study was to evaluate
the genetic diversity of eight cattle breeds in China based on microsatellite
markers and to estimate the genetic relationships among these eight breeds.