INDIVIDUAL MULTILOCUS GENOTYPES USING MICROSATELLITE POLYMORPHISMS TOPERMIT THE ANALYSIS OF THE GENETIC-VARIABILITY WITHIN AND BETWEEN ITALIAN BEEF-CATTLE BREEDS

We investigated the genetic variability within and between cattle bree ds. The polymorphisms of 17 microsatellites were studied in 220 unrela ted animals belonging to four Italian beef cattle breeds (Chianina, Ma rchigiana, Romagnola, and Piemontese). Variations of allelic frequenci es were examined to characterize the breeds and their relationships. W ahlund coefficients, Polymorphism Information Content values, and Hald ane exact test for Hardy-Weinberg proportions were calculated. The res ults show that the Hardy-Weinberg equilibrium is not always maintained . Moreover, in addition to the classical genetic distances, a new meth od, based on the consideration of a multilocus genotype of each animal , was set up to measure the genetic similarity between animals or with in groups of animals. All the results showed that, whereas Chianina oc cupies an intermediate position and Piemontese is the most distinct of all four breeds, Marchigiana and Romagnola display the strongest simi larity. The new method also provides evidence that average similaritie s are always higher within breeds than between breeds. By comparing pa irwise the multilocus genotypes, it was also possible to discriminate the individuals with higher or lower genetic similarities so that each breed could be subdivided into two groups of animals in relation to t heir similarity to the average breed multilocus genotype. High similar ities between breeds were detected, somewhat surprisingly, when the mo st homogeneous groups of each breed were compared. The microsatellite multilocus genotype is particularly efficient in evaluating the betwee n- and within-breeds genetic similarities and for subgrouping genetica lly more homogeneous animals.