Studies On Molecular Genetic Diversity Of Chinese Local Chicken Breeds

China, as one of the largest chicken producers in the world, is rich in chicken genetic resources, and there are many local breeds scattered throughout the country. These breeds vary in size, plumage color and other characteristics. Most of them are often maintained in small populations given their low to medium performance in egg production and growth rate. Being less productive, they are threatened by the commercial varieties utilized by large domestic and foreign breeding companies. Seventy-eight local chicken breeds have been surveyed and their blood samples collected. Then the genetic diversity of these breeds was analyzed by microsatellite markers and mtDNA D-loop respectively.(1) The improvement of methods to detect biodiversity: DNA silver staining is widely used in many labs with high sensitivity to detect trace DNA in polyacrylamide gel. However, most of silver staining methods are time-consuming (about 30min~2hrs) and need many steps which decrease efficiency. A new protocol for DNA silver staining presented in this study displayed high sensitivity and more timesaving than other silver staining methods and was compared with other three widely used methods. The procedure was improved on the basis of a standard one and almost halved the number of steps (only 4), solutions and experimental time (about 20mins) required and almost had no effect on the sensitivity of silver staining. Microsatellete PCR products were detected by non-denatured and denatured PAGE gels respectively and the gels were dyed by silver. There were distinct differences between the two kinds of gel. In non-denatured gels, many nonspecific bands were found while clear target bands were showed in denatured gels.(2) The genomes of these chickens were screened using microsatellite analysis. Approximately 3,000 individuals were genotyped for 27 microsatellite markers on 13 chromosomes. Of the 27 microsatellite loci, the number of alleles ranged from 6 to 51 per locus. The average heterozygosity value (H, 0.622) and polymorphism information content (PIC, 0.573) suggests that the Chinese chickens possess more genetic diversity than that in many other countries. Further, using Nei's standard distance, Nei's distance, the Neighbor-Joining and UMPGA method, the local Chinese chickens were classified into six categories including North-west type, South type, South-west I type, South-west II type, East type, Centre type. The cluster results were generally consistent with their geographic distributions.(3) As a special class of chickens, games are different in backgrounds and functions from normal chicken breeds. At present, there are five game breeds in China. However, the genetic relationships and structure of Chinese games were totally unclear, and it was very important to make clear the genetic relationships of Chinese game chickens which could provide academic basement forfurther conservation and utilization. Blood samples of five Chinese game breeds were collected in this study, and 7 or 8 genome DNA samples in each breed were extracted for amplifying the mtDNA D-loop (about 560bp). Two statistical methods were used to cluster the Chinese games with 39 mtDNA sequences. Two phylogenetic tree constructed in the study showed the genetic relationships among breeds depended on their locations. Distinct differences existed between Zhangzhou Game chicken and other local chicken breeds and two origins of Chinese local game chickens were found.