BIOCHEMICAL POLYMORPHISMS AND GENETIC-RELATIONSHIPS AMONG LANDRACE, LARGE WHITE AND DUROC PIGS FROM SOUTHERN BRAZIL

Fourteen protein systems encoded by 15 structural loci were used to in vestigate genetic variability in three swine breeds (Landrace, Large W hite and Duroc), reared in Southern Brazil. The degree of genetic vari ability was similar in the three breeds (Landrace, HeBAR - 0.116; Larg e White, HeBAR - 0.119; Duroc, HeBAR = 0.095). These values are close to those computed for other populations of these breeds and higher tha n those obtained for wild pig populations. The gene frequencies at the polymorphic loci were employed to evaluate the usefulness of these sy stems for parent identification. The combined probabilities of paterni ty exclusion were estimated at 59% for Landrace, 54% for Large White a nd 50% for Duroc animals. Analysis of genetic relationships revealed t hat Landrace and Large White are the most similar breeds (D - 0.044), while the Duroc breed presents lower levels of genetic similarity to t he other two breeds (Landrace/Duroc: D - 0.084; Large White/Duroc: D - 0.106). These findings are in agreement with the historical developme nt of these breeds.