Studies On Heterosis Of The Meat Sheep Using Microsatellite Markers

Crossbreeding is one of the most effective methods to get highest productivity for lamb. In recently years, some excellent meat sheep were introduced in our country to use their heterosis, develop inherent potentiality of specific character, decrease the production cost, and enhance the quality and competing power of lamb in market. Traditional method to forecast heterosis of animals is inconvenient because the testing to their combining ability is necessary. In contrast with this method, the microsatellite DNA marker is more helpful, it was used to analysis the genetic constitution, genetic variation and genetic relationship of three abroad variety (Suffolk,Dorset and Texel), that were of better meat production and adaptability to environments.So did their three first filial generation (Suffolk×little-tailed han sheep,Dorset×little-tailed han sheep, Texel×little-tailed han sheep).The genetic distance between the three abroad breeds and three crossing populations was calculated by method of Nei's standard genetic distance, it was indicated that three-way hybrid combination of Dorset×little-tailed han sheep×Texel is best one under existing condition.The genetic constitution and genetic variation of three introduced breeds and three hybrid sheep populations were studied using six microsatellite markers. Mean polymorphism information contents, the number of alleles, number of effective alleles and heterozygsity of every groups from six microsatellite loci are 0.7570～0.8621,8.3333～11.5000,4.9971～8.2300 and 0.7826～0.8753 respectively, which were calculated according to allele frequency by POPGENE program. The four genetic indexes from six population are 0.7664～0.8445,7.5000～10.0000,5.1854～7.2312 and 0.7878～0.8598 respectively. The result showed that polymorphism information contents of every population at six microsatellite loci are more than 0.5, it also showed that six microsatellite loci in every population were of the high polymorphism and the genetic variation is very abundant. There was a large selection potential also in the three abroad breeds and three crossing populations.Moreover, The genetic distance between the three abroad breeds and three crossing populations was calculated using method of Nei's standard genetic distance. To predicate heterosis, the best cross combination between three abroad breeds and three crossbreeds was determined according to genetic relationship. The genetic distance (0.4273) between Dorset-little tailed sheep and Texel was biggest. Their order of genetic distance from large to small was Dorset-little sheep tailed and Suffolk (0.4081) > Texel-little tailed han sheep and...