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* Estação Zootécnica Nacional – INRB, 2005-048 Vale de Santarém, Portugal
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Escola Superior Agrária de Santarém, Apartado 310, 2001-904 Santarém, Portugal
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Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal; #Departamento de Genética, Universidad de Córdoba, Edifício Gregor Mendel, Campus de Rabanales s/n, 14071 Córboda, Spain
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Laboratório de Genética Molecular, Servicio de Cria Caballar y Remonta, Apartado Oficial Sucursal 2, 14071 Córdoba, Spain
1 Faculdade de Medicina Veterinária - Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal
genetica.ezn{at}mail.telepac.pt
Abstract
Population structure and genetic diversity in the Portuguese native breeds of pigs Alentejano (AL), Bisaro (BI), and Malhado de Alcobaça (MA), and the exotic breeds Duroc (DU), Landrace (LR), Large White (LW), and Pietrain (PI), were analyzed by typing 22 microsatellite markers in 249 individuals. In general, the markers used were highly polymorphic, with means for total and effective number of alleles per locus of 10.68 and 4.33, respectively, and an expected heterozygosity of 0.667 across loci. The effective number of alleles per locus and expected heterozygosity were highest in BI, LR, and AL, and lowest in DU. Private alleles were found in 9 of the 22 markers analyzed, mostly in AL, but also in the other breeds, with the exception of LW. The proportion of loci not in Hardy-Weinberg equilibrium in each breed analyzed ranged between 0.23 (AL) and 0.41 (BI, LW and PI), mostly due to a lower than expected number of heterozygotes in those loci. With the exception of MA, all breeds showed a significant deficit in heterozygosity (P<0.05), which was more pronounced in BI (FIS = 0.175) and AL (FIS = 0.139), suggesting that inbreeding is a major concern, especially in these breeds, which have gone through a genetic bottleneck in the recent past. The analysis of relationships among breeds, assessed by different methods, indicates that DU and AL are the more distanced breeds relative to the others, with the closest relationship being observed between LR and MA. The mean FST indicates that 0.184 of the total genetic variability can be attributed to differences among breeds. The analysis of individual distances based on allele-sharing indicates that animals of the same breed generally cluster together, but subdivision is observed in the BI and LR breeds. Furthermore, the analysis of population structure indicates there is very little admixture among breeds, each one being identified with a single ancestral population. The results of this study confirm that native breeds of pigs represent a very interesting reservoir of allelic diversity, even though the current levels of inbreeding raise concerns. Therefore, appropriate conservation efforts should be undertaken, adopting strategies aimed at minimizing inbreeding, to avoid further losses of genetic diversity.
Key Words: diversity • genetic variability • microsatellites • native breeds • pig
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  C. Dalvit, M. De Marchi, E. Zanetti, and M. Cassandro Genetic variation and population structure of Italian native sheep breeds undergoing in situ conservation J Anim Sci, December 1, 2009; 87(12): 3837 - 3844. [Abstract] [Full Text] [PDF]
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