Genotype data from 30 microsatellites were used to assess genetic diversity and relationships among 10 native Portuguese cattle breeds, American Charolais and the Brazilian Caracú. Hardy-Weinberg equilibrium was observed for all loci/population combinations except for five loci in Brava de Lide and one locus in Alentejana that exhibited heterozygote deficiency. Estimates of average observed and expected heterozygosities, total number of alleles (TNA) per breed and mean number of alleles (MNA) per locus/population were obtained. A total of 390 alleles were detected. TNA among Iberian cattle ranged from 170 to 237 and MNA ranged from 5.67 to 8.07. The highest observed heterozygosities were found in the Caracú, Maronesa, Garvonesa and Arouquesa and the lowest in Brava de Lide and Mirandesa. Estimation of population subdivision using Wright's FST index showed that the average proportion of genetic variation explained by breed differences was 9%. Neighbour-joining phylogenetic trees based on DA distances showed that the genetic relationships of present-day Portuguese native breeds are consistent with historical origins in the Brown Concave (Arouquesa, Mirandesa, Marinhoa) and Red Convex (Mertolenga, Alentejana, Garvonesa, Minhota) evolutionary groups. The Iberian Black Orthoide group, represented by Brava de Lide and Maronesa, and the Barrosã breed appeared to be more closely related to the Brown Concave group but may represent a separate lineage. The Caracú breed was not found to be closely associated with any of the native Portuguese breeds.

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A new Robertsonian translocation, rob(l 5;25), was discovered in a Portuguese Barrosa cow. The animal (2n = 59, XX) was found by G- and R-banding to be a heterozygous carrier of a centric fusion translocation involving chromosomes 15 and 25. C-banding revealed the dicentric nature of this new centric fusion. Comparison of this new translocation with the well-known Robertsonian translocation rob(l;29), which is often found in the same breed, confirmed that two different chromosomes (25 and 29) were involved in the short arms of these two Robertsonian translocations.

Representative samples of Portuguese cattle from Barrosg, Maronesa, and Mirandesa breeds underwent cytogenetic investigation. Banding showed that 134 (65.0 %) Barrosas, 74 (40.2 %) Maronesas and 4 (1.6 %) Mirandesas carried rob (1;29). "be frequency of this translocation in the three breeds (39 % in Barrosas, 23 % in Maronesas, and I % in Mirandesas) was in a genetic Hardy-Weinberg equilibrium for the three karyological forms (2n = 60, 2n = 59 and 2n = 58), strongly supporting the hypothesis for an ancient origin of this translocation and the hypothesis of the origin of Maronesas from BarrosP and Mirandesa cross-breeding. The total Portuguese cattle population numbers about one million, including both local and imported breeds (D.G.P. 1987). BarrosB, Maronesa, and Mirandesa (about 10 % of all Portuguese cattle) are raised primarily for meat production in three different but geographically similar regions of North-Portugal (West, Middle, and East, respectively). Barrosas are believed to have originated from the Mauritanian cattle (North-Africa), and Mirandesas from Berciana and Verinesa Spanish breeds (MASON 1988). It has been hypothesized that Maronesas derived from BarrosB and Mirandesa crossbreeding (MASON 1988), but no direct evidence has been reported.Previous cytogenetic studies have shown high frequencies of rob (1;29) in Maronesas and Barrosas ( RANGEL- IANNUZZI 1990, 1991). In the present study we included for the first time a representative sample of Mirandesas as well as a larger number of Barrosas and, primarily, of Maronesas, than in previous studies. We found that the three populations show frequencies of rob (1;29) which are in a genetic Hardy-Weinberg equilibrium for the three karyological forms (2n = 60, 2n = 59 and 2n = 58) and support the hypothesis for the origin of Maronesas from the other two breeds. Materials and methodsTwo hundred-forty-four Mirandesas (5 1 males and 193 females), 184 Maronesas (82 males and 102 females), and 206 Barrosas (27 males and 179 females), randomly sampled from 38, 26, and 55 small farms, respectively, underwent a cytogenetic investigation.Peripheral blood was cultured for 72 h at 38.5"C in RPMI 1640 (Gibco) medium with L-glutamine (1 YO), Pokeweed mitogen (1 %), and autologous plasma ( 15 YO). Six hours before harvesting, 20 pg/ ml of 5-Bromodeoxyuridine (BrdU) were added for R-banding. Colcemid treatment (0.05 /*g/ml) lasted one hour. A hypotonic treatment (0.5 % KCl) and four fixations (the third overnight) in methanol/acetic acid (3: 1) followed.Additional cultures from 10 heterozygous Mirandesa and Maronesa carriers; were set up with early-BrdU incorporation to obtain G-banding patterns, as previously reported (IANNUZZI et al. 1989).CBG-(SUMNER 1972), RBA-(IANUZZI 1990), and GBA + CBA- (IANNUZZI et al. 1989) banding techniques were used. G-and R-banded karyotypes were arranged according to ISCNDA (1989).

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