Genetic Diversity Analyses Of 10 Indigenous Chinese Pig Populations Based On 20 Microsatellites

To study the genetic diversity of Chinese indigenous pig breeds, a total of 403 pigs from 10 local populations and 1 exotic Duroc breed were genotyped for 20 microsatellite markers. Heterozygosity and Wright's F-statistics (FIS, FST, and FIT were calculated to determine the genetic variation in those populations. The observed heterozygosities were in the range of 0.31 (Duroc) to 0.66 (Shengxian). The FIS value was in a range of -0.07 to 0.48. The mean FST showed that approximately 78% of the genetic variation was within-population and 22% was across the populations. The 10 Chinese indigenous breeds were classified into two major groups according to the phylogenetic tree, which was based on standard genetic distance. Four pig populations, Jianli, Ganxi Two Ends Black, Shaziling, and Dongshan were grouped into one branch. Before the study, these four populations were all classified as Central China Two-Ends-Black according to coat color, shape of the head, and shape of the ear. The Jinhua pig, which also has the two-ends-black coat color, was also grouped to the same branch but was not traditionally classified into this type. The five populations were located in various provinces in central China. The other five populations, Nanyang Black, Hainan Spotted, Huainan Black, Jiaxing Black, and Shengxian Spotted (black body, white feet), were grouped into another branch. The two groups of pig breeds had the same FsT value (0.14) when calculated separately. This value was similar to that of Iberian pigs (0.13) but smaller than that of the European pigs (0.27) as reported by other researchers.Our study showed that large genetic differentiation exists in Chinese pig breeds. The grouping of the five two-ends-black populations into one branch of the phylogenetic tree may indicate that the number of conservation farms can be decreased for this type of pig. China has at least a 7,000-yr history of domesticating pigs (Zhang, 1986) Over 100 pig breeds, about a third of the world's pig breeds, exist in China (Li et al., 2000a ). They were classified into six types according to their geographic origin, distribution, body conformation, and coat color: North China, Lower Changjiang Basin, Central China,South China, Southwest, and Plateau (Zhang, 1986). Each type contains a number of breeds. It will be interesting to examine the genetic relationship among local pig breeds by molecular markers such as microsatellites and to compare them to the traditional classification results. Microsatellites have been widely used for genetic variation studies in domestic animals. In the pig, genetic diversity studies of some of the commercial breeds and the Chinese Meishan breed were conducted by genotyping multiple microsatellite loci (Johansson et al., 1992; Fredholm et al., 1993 ; Paszek et al., 1998a ,b ), and the results showed that the Meishan has a significantly higher mean heterozygosity than the Western breeds (Yorkshire, Hampshire, Duroc, Landrace), as observed at several microsatellite loci (Paszek et al., 1998b ). Genetic diversity of some Chinese local breeds investigated by using microsatellites suggested a higher (Li et al., 2000b ) or similar (Fan et al., 2002 ) genetic differentiation among breeds compared with that of Belgian, exotic breeds (British Larger White, Yorkshire, Hampshire), and European breeds (van Zeveren et al., 1995 ; Kacirek et al., 1998 ; Laval et al., 2000 ; Martinez et al.,2000 ). In this study, we used 20 pairs of microsatellite primers to detect the genetic relationship between 10 local pig populations and to compare two breed-classification methods based on traditional methods or microsatellites.