RESUMO
Single nucleotide polymorphism (SNP) markers are used to study population structure and conservation genetics, which permits assessing similarities regarding the linkage disequilibrium and information about the relationship among individuals. To investigate the population genomic structure of 300 females and 25 males from a commercial maternal pig line we analyzed linkage disequilibrium extent, inbreeding coefficients using genomic and conventional pedigree data, and population stratification. The average linkage disequilibrium (r2) was 0.291 ± 0.312 for all adjacent SNPs, distancing less than 100 Kb (kilobase) between markers. The average inbreeding coefficients obtained from runs of homozygosity (ROH) and pedigree analyses were 0.119 and 0.0001, respectively. Low correlation was observed between the inbreeding coefficients possibly as a result of genetic recombination effect accounted for the ROH estimates or caused by pedigree identification errors. A large number of long ROHs might indicate recent inbreeding events in the studied population. A total of 36 homozygous segments were found in more than 30% of the population and these ROH harbor genes associated with reproductive traits. The population stratification analysis indicated that this population was possibly originated from two distinct populations, which is a result from crossings between the eastern and western breeds used in the formation of the line. Our findings provide support to understand the genetic structure of swine populations and may assist breeding companies to avoid a high level of inbreeding coefficients to maintain genetic diversity, showing the effectiveness of using genome-wide SNP information for quantifying inbreeding when the pedigree was incomplete or incorrect.
Assuntos
Desequilíbrio de Ligação , Polimorfismo de Nucleotídeo Único , Suínos/genética , Animais , Feminino , Genética Populacional , Endogamia , MasculinoRESUMO
Whole-genome re-sequencing, alignment and annotation analyses were undertaken for 12 sires representing four important cattle breeds in Brazil: Guzerat (multi-purpose), Gyr, Girolando and Holstein (dairy production). A total of approximately 4.3 billion reads from an Illumina HiSeq 2000 sequencer generated for each animal 10.7 to 16.4-fold genome coverage. A total of 27,441,279 single nucleotide variations (SNVs) and 3,828,041 insertions/deletions (InDels) were detected in the samples, of which 2,557,670 SNVs and 883,219 InDels were novel. The submission of these genetic variants to the dbSNP database significantly increased the number of known variants, particularly for the indicine genome. The concordance rate between genotypes obtained using the Bovine HD BeadChip array and the same variants identified by sequencing was about 99.05%. The annotation of variants identified numerous non-synonymous SNVs and frameshift InDels which could affect phenotypic variation. Functional enrichment analysis was performed and revealed that variants in the olfactory transduction pathway was over represented in all four cattle breeds, while the ECM-receptor interaction pathway was over represented in Girolando and Guzerat breeds, the ABC transporters pathway was over represented only in Holstein breed, and the metabolic pathways was over represented only in Gyr breed. The genetic variants discovered here provide a rich resource to help identify potential genomic markers and their associated molecular mechanisms that impact economically important traits for Gyr, Girolando, Guzerat and Holstein breeding programs.
Assuntos
Bovinos/genética , Mutação INDEL , Polimorfismo de Nucleotídeo Único , Animais , Brasil , Cruzamento , Bovinos/classificação , Feminino , Genótipo , Sequenciamento de Nucleotídeos em Larga Escala/veterinária , Masculino , Anotação de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos/veterinária , Análise de Sequência de DNA/veterinária , Especificidade da EspécieRESUMO
The aim of this study was to estimate genetic parameters for accumulated productivity (ACP), first calving interval (CI1), second calving interval (CI2), and mean calving interval (MCI) in Nelore beef cattle. The ACP trait is a reproduction index and comprises the total number of calves born per dam, weight of weaned calves, and age of the dam at calving. Genetic parameters were estimated by the average information restricted maximum likelihood method in two-trait analyses. The average heritability estimate for ACP was 0.17 (0.03). For CI1, CI2, and MCI, the heritability estimates were 0.02, 0.02, and 0.06, respectively. Genetic correlations between ACP with CI1, CI2, and MCI were -0.16 ± 0.47, -0.29 ± 0.53, and -0.40 ± 0.27, respectively. Despite of the low heritability estimates obtained in our study, reproduction traits should be further studied and their inclusion in the selection criteria must be evaluated in order to improve the performance of females because these traits are of great economic importance in beef cattle. Accumulated productivity could contribute to decrease the mean calving interval in Nelore cattle.