Caracterização genômica de equinos das linhagens de trabalho e de corrida da raça Quarto de Milha
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Data
2018-04-20
Autores
Marchiori, Cíntia Maria
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Universidade Estadual Paulista (Unesp)
Resumo
Na raça Quarto de Milha de equinos (Equus caballus), diferentes objetivos de seleção levaram à formação de linhagens com distintas habilidades, entre as quais a de trabalho e a de corrida. A linhagem de trabalho destina-se às provas de caráter funcional, explorando habilidades como agilidade e obediência, características consideradas de grande importância no manejo do gado a campo. Os animais de corrida apresentam melhor desempenho em pistas de curtas distâncias do que qualquer outra raça de equinos. O objetivo deste estudo foi caracterizar, por meio da genotipagem de SNP em larga escala, o desequilíbrio de ligação (LD), calculado por r², nas linhagens de trabalho e de corrida de cavalos Quarto de Milha criados no Brasil. Também foi investigado o tamanho efetivo (Ne) das duas populações, bem como as suas estruturas e relações. Para tanto, foram utilizados 428 equinos Quarto de Milha, de ambos os sexos, registrados na associação Brasileira de criadores da raça (ABQM), sendo 68 da linhagem de trabalho e 360 da de corrida. Estes animais tiveram o sangue colhido no Jockey Club de Sorocaba (Sorocaba/SP) e em propriedades rurais localizadas em dezenas de cidades do interior do Estado de São Paulo. Cento e oitenta e oito animais, 68 da linhagem de trabalho e 120 da de corrida foram genotipados, no ano de 2011, utilizando arranjo de 54.602 SNP (54K). As demais amostras da linhagem de corrida (n = 240) foram genotipadas, no ano de 2015, com arranjo de 65.157 SNP (65K). Após a realização de processo de imputação, o número de SNP informativos na linhagem de corrida foi de 55.114. Desta forma, para as análises genéticas subsequentes realizadas nas linhagens de trabalho e de corrida foram utilizados 43.117 e 55.114 SNP, respectivamente. O r² genômico médio entre pares de marcadores foi 0,22 para a linhagem de trabalho e 0,27 para a de corrida. Na linhagem de trabalho o r² foi inferior a 0,2 entre 100 e 150 Kb, enquanto na de corrida foram encontrados valores de r² menores que 0,2 entre 300 e 350 Kb. A estimativa dos valores de Ne foi de 60 e 50 animais na última geração para as linhagens de trabalho e de corrida, respectivamente. A maior extensão do LD e o menor Ne na linhagem de corrida podem ser explicados pela sua estrutura populacional mais fechada em decorrência do maior rigor no registro genealógico dos animais, além da grande influência do Puro-Sangue Inglês na sua formação. O estudo da estrutura da população indicou clara distinção entre as duas linhagens da raça. Na linhagem de corrida, contudo, foram evidenciadas substruturas populacionais decorrentes da formação de famílias que descendem de diferentes e importantes reprodutores.
In the Quarter Horse breed (Equus caballus), different selection objectives led to the formation of lineages with different abilities, including cutting and racing. The cutting line intended for functional tests, exploring skills such as agility and obedience, characteristics considered of great importance in the management of cattle. Racing animals perform better on runways short distances than any other horse breed. The objective of this study was to characterize, by means of large-scale SNP genotyping, the linkage disequilibrium (LD), calculated by r², in the cutting and racing lines of Quarter Horses created in Brazil. The effective size (Ne) of the two populations was investigated, as well as their structures and relationships. For that, 428 Quarter Horses of both sexes, registered in the Brazilian Association of Breeders (ABQM) were used, of which 68 were from the cutting line and 360 from the racing. These animals had blood collected at the Jockey Club of Sorocaba (Sorocaba/SP) and on rural properties located in dozens of cities in the interior of the São Paulo State. One hundred and eighty-eight animals, 68 of the cutting line and 120 of the racing were genotyped in the year 2011, using a 54,602 SNP array (54K). The other racing line samples (n = 240) were genotyped in 2015, with an array of 65,157 SNP (65K). After the imputation process, the number of informative SNP in the racing line was 55,114. Thus, for the subsequent genetic analyzes performed on the cutting and racing lines, 43,117 and 55,114 SNP were used, respectively. The mean genomic r² between pairs of markers was 0.22 for the cutting line and 0.27 for the racing. In the cutting line the r² was less than 0.2 between 100 and 150 Kb, while in the racing r² values were lower than 0.2 between 300 and 350 Kb. The estimates of Ne values were 60 and 50 animals in the last generation for the cutting and racing lines, respectively. The longer extent of the LD and the smaller Ne in the racing line can be explained by its more closed population structure due to the greater rigor in the genealogical register of the animals, further on the great influence of the Thoroughbred in its formation. The population structure study indicated a clear distinction between the two lineages of the breed. However, in the racing line, population substructures were evidenced due to the formation of families that descend from different and important stallions.
In the Quarter Horse breed (Equus caballus), different selection objectives led to the formation of lineages with different abilities, including cutting and racing. The cutting line intended for functional tests, exploring skills such as agility and obedience, characteristics considered of great importance in the management of cattle. Racing animals perform better on runways short distances than any other horse breed. The objective of this study was to characterize, by means of large-scale SNP genotyping, the linkage disequilibrium (LD), calculated by r², in the cutting and racing lines of Quarter Horses created in Brazil. The effective size (Ne) of the two populations was investigated, as well as their structures and relationships. For that, 428 Quarter Horses of both sexes, registered in the Brazilian Association of Breeders (ABQM) were used, of which 68 were from the cutting line and 360 from the racing. These animals had blood collected at the Jockey Club of Sorocaba (Sorocaba/SP) and on rural properties located in dozens of cities in the interior of the São Paulo State. One hundred and eighty-eight animals, 68 of the cutting line and 120 of the racing were genotyped in the year 2011, using a 54,602 SNP array (54K). The other racing line samples (n = 240) were genotyped in 2015, with an array of 65,157 SNP (65K). After the imputation process, the number of informative SNP in the racing line was 55,114. Thus, for the subsequent genetic analyzes performed on the cutting and racing lines, 43,117 and 55,114 SNP were used, respectively. The mean genomic r² between pairs of markers was 0.22 for the cutting line and 0.27 for the racing. In the cutting line the r² was less than 0.2 between 100 and 150 Kb, while in the racing r² values were lower than 0.2 between 300 and 350 Kb. The estimates of Ne values were 60 and 50 animals in the last generation for the cutting and racing lines, respectively. The longer extent of the LD and the smaller Ne in the racing line can be explained by its more closed population structure due to the greater rigor in the genealogical register of the animals, further on the great influence of the Thoroughbred in its formation. The population structure study indicated a clear distinction between the two lineages of the breed. However, in the racing line, population substructures were evidenced due to the formation of families that descend from different and important stallions.
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Palavras-chave
BeadChip, cavalo, marcadores moleculares, polimorfismos de DNA, tamanho efetivo, horse, molecular markers, DNA polymorphisms, effective size