Análise genômica da estrutura populacional em cavalos da raça brasileira Mangalarga Marchador
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Data
2019-02-28
Autores
Santos, Bruna Aparecida dos
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Universidade Estadual Paulista (Unesp)
Resumo
O Mangalarga Marchador é o cavalo de sela brasileiro, possui dois tipos de andamentos característicos, a marcha batida e a marcha picada, que proporcionam maior comodidade ao cavaleiro durante a cavalgada e o trabalho. É principalmente utilizado para trabalho em fazendas de gado de corte e vem se destacando em diferentes modalidades de esportes hípicos. Este estudo teve como objetivo caracterizar, por meio da genotipagem de SNP em larga escala, o desequilíbrio de ligação (LD), calculado por r², de equinos da raça brasileira Mangalarga Marchador criados no Brasil. Também foi investigado o tamanho efetivo (Ne) da população, bem como as suas estruturas e relações. Foram utilizados 240 equinos Mangalarga Marchador, de ambos os sexos, e registrados na associação brasileira de criadores da raça (ABCCMM). O número de SNP informativos foi de 377.308. Análises de componentes principais mostraram que cavalos Mangalarga Marchador de marcha batida e de marcha picada pertencem a uma mesma população, ou seja, estes grupos não segregaram de forma significativa dentro da raça, o que deve ser levado em consideração nos estudos genético-populacionais. O r² genômico calculado foi de 0,096±0,166. O LD decaiu consideravelmente a partir de distâncias superiores a 15 e 20 Kb, apresentando valores inferiores a 0,3 e 0,2, respectivamente. O Ne atual foi de 99 animais. Houve acentuada redução neste parâmetro ao se tomar as estimativas de 16 gerações passadas, em que o Ne estimado foi de 650 animais. Estes resultados podem estar ligados à uma base genética ampla e parcialmente aberta e à pressões de seleção crescentes na raça. Por fim, observou-se subestruturas populacionais definidas relacionadas mais à importantes reprodutores da raça do que propriamente ao tipo de marcha.
The Mangalarga Marchador is the Brazilian saddle horse, has two types of characteristic movements, the batida and the picada gait, that provide greater comfort to the rider during the cavalcade and the work. It is mainly used for work on beef cattle farms and has been emphasizing different modalities of equestrian sports. The objective of this study was to characterize, by means of large scale SNP genotyping, the linkage disequilibrium (LD), calculated by r², of Brazilian Mangalarga Marchador breed horses raised in Brazil. We also investigated the effective size (Ne) of the population, as well as their structures and relationships. A total of 240 Mangalarga Marchador horses, of both sexes, and registered in the Brazilian association of breeders (ABCCMM) were used. The number of informative SNPs was 377,308. Principal component analyzes showed that Mangalarga marchador of the two diferente gaits belong to the same population, that is, these groups did not segregate significantly within the breed, which should be taken into account in the genetic-population studies. The calculated r² genomic was 0.096 ± 0.166. The LD declined considerably from distances greater than 15 and 20 Kb, presenting values lower than 0.3 and 0.2, respectively. The current Ne was 99 animals. There was a marked reduction in this parameter when taking the estimates of 16 generations passed, in which the estimated Ne was 650 animals. These results may be linked to a broad and partially open genetic basis and to increasing selection pressures in the breed. Finally, we observed defined population substructures related to the breed's important breeders rather than to the type of gait.
The Mangalarga Marchador is the Brazilian saddle horse, has two types of characteristic movements, the batida and the picada gait, that provide greater comfort to the rider during the cavalcade and the work. It is mainly used for work on beef cattle farms and has been emphasizing different modalities of equestrian sports. The objective of this study was to characterize, by means of large scale SNP genotyping, the linkage disequilibrium (LD), calculated by r², of Brazilian Mangalarga Marchador breed horses raised in Brazil. We also investigated the effective size (Ne) of the population, as well as their structures and relationships. A total of 240 Mangalarga Marchador horses, of both sexes, and registered in the Brazilian association of breeders (ABCCMM) were used. The number of informative SNPs was 377,308. Principal component analyzes showed that Mangalarga marchador of the two diferente gaits belong to the same population, that is, these groups did not segregate significantly within the breed, which should be taken into account in the genetic-population studies. The calculated r² genomic was 0.096 ± 0.166. The LD declined considerably from distances greater than 15 and 20 Kb, presenting values lower than 0.3 and 0.2, respectively. The current Ne was 99 animals. There was a marked reduction in this parameter when taking the estimates of 16 generations passed, in which the estimated Ne was 650 animals. These results may be linked to a broad and partially open genetic basis and to increasing selection pressures in the breed. Finally, we observed defined population substructures related to the breed's important breeders rather than to the type of gait.
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Palavras-chave
Desequilíbrio de ligação, Estruturas populacionais, SNP, Tamanho efetivo