Study On Relationship Between Heterosis Of Growth Traits For Beef And Genetic Distance By Microsatellite Markers

Eight beef or dual-purpose cattle breeds were introduced in this study, including Simmental, Limousin, Angus, Red Angus, Blonde d'Aquitaine, Low line, Hereford, Gelbvieh and so on. The frozen semen or herd sire from eight breeds were crossed with local cattle (Chuannan mountainous cattle). By measuring the growth and development traits of neonatal, 3,6, 12, 18 and 24-month-old hybrid offsping, the improvement effect of different cross combination on body weight and size of local cattle.was studied, and the HP (over-parent heterosis) also was calculated. The genetic structure and variation of eight beef or dual-purpose cattle and Chuannan mounta-inous cattle populations were analyzed by microsatellite markers. Through studying the relationship between heterosis and parental genetic distance,the method of heterosis prediction was researched.The results showed that:1. In terms of body weight and size, hybrids were higher than Chuannan mountainous cattle. Throughout the experimental phases, the breeds which improved more weight were Hereford×Chuannan, Simmental×Chuannan, Red Angus×Chuannan and Gelbvieh×Chuannan hybrids, improved more overall withers height were Hereford×Chuannan and Simmental×Chuannan hybrids, improved more overall body length were Simmental×Chuannan, Hereford×Chuannan, Red Angus×Chuannan and Gelbvieh×Chuannan hybrids, improved more body straight length were Hereford×Chuannan and Simmental×Chuannan hybrids, and improved more chest girth and cannon circumference were Simmental×Chuannan, Hereford×Chuannan, Red Angus×Chuannan hybrids. In general, the breeds which got superior geneticimprovement effects on Chuannan cattle growth traits were Hereford, Simmental and Angus.2. A total of 80 alleles in nine populations were detected by 11 microsatellite loci, the average number of alleles per locus was 7.27, average effective number of alleles pe, locus was from 3.0069 to 4.9912, average polymorphsm information content per locus was from0.3566 to 0.4098, average heterozygosity per locus was fiom 0.6854 to 0.7918 and the average group heterozygosity was from 0.6591 to 0.8413.3. The genetic consistency of Chuannan mountain cattle was low, with the average heterozygosity by 11 microsatellite loci of 0.8413.4. Based on allele frequency of 11 microsatellite loci in nine species, standard genetic distance was caculated, the genetic distance between Chuannan mountainous and introduced cattle were listed from large to small: Angus 0.5068, Limousin 0.3257, Hereford 0.2910, Low Line 0.2409, Red Angus 0.2082, Simmental 0.1500, Gelbvieh0.1447 and Blond d'Aquitaine 0.1009, respectively. The clustering dendrograph was drawn by UPGMA method using genetic distance from partial groups: Germany and Simmental clustered together, and then clustered with local cattle as the second category, then clustered with Red Angus, Limousinas the third and fourth categories, finally clustered with black Angus cattle.5. The relationship between microsatellite genetic distance and heterosis was analyzed by the coefficient of rank correlation (Spearman rank correlation), the result was: r_s=0.16071 (P＞0.05), and the correlation was not significant.6. The advantages and disadvantages of different cross combinations in Three Gorges reservoir area (by paternal parent) were evaluated by the means of molecular quantitative genetics, and ranked as: Hereford, Red Angus, Simmental, Blonde d'Aquitaine, Black Angus, Limousin, Gelbvieh and Low Line.