Uso de seleção assistida por marcadores moleculares em melhoramento genético de suínos

Abstract

ABSTRACT: With the advancement of knowledge about the animal genome, the production of pigs benefits from the new molecular tools in search of the best zootechnical, results such as feed efficiency, number of piglets weaned / sow year, higher meat production in the carcass, better yield of meat cuts. Thus, the use of molecular markers selects the best genotypes for the desired characteristics, allowing shorter generation time, lower cost to producers, higher yields of products for industry and better quality for consumers. The work was divided into two stages where the first study sought to evaluate in a population of 272 Large White matrices the polymorphisms of the DGAT1, LEPR, HFABP, MC4R, SREBF1 genes by the ARMS- PCR technique and for the pGH gene polymorphism the PCR-RFLP technique was used. Genomic DNA was extracted from the hair bulb. The primers were designed for each of the genes using the sequences deposited in GenBanK. After DNA sequencing no polymorphisms were found, with the exception of the MC4R marker which showed 100% heterozygosity. Considering the initial population, 209 samples were genotyped for the pGH gene, where a 605 base pair amplicon was digested by restriction enzyme DdeI, resulting in two alleles. The D1 allele with 335,148 and 122 pb and the D2 allele with 457 and 148 pb. The genotypic frequency of D1D2 was 88% and for D2D2 22%. The D1 allele had a frequency of 11% and for D2 of 89%. The high intensity of selection for commercial breeds justifies the absence or the low number of polymorphisms for the genes studied. For the second part of the research, we aimed to associate pGH / DdeI polymorphism with carcass characteristics and meat quality. A population of 476 animals from the crossing of the AGPIC 415 male and LW X LD females free from the halothane gene mutation, castrated males and females aged 150 to 180 days. The information were collected as warm carcass weight, carcass length, pH 45min and pH ± 16h postmortem of the muscles Longíssimos cervicis, Longíssimos dorsi and Semimebranosus, backfat thickness, LD muscle depth and color by the CIELAB system. The water holding capacity was determined by the filter paper method in the Semimebranosus muscle and the percentage of lean meat was calculated. A SNP at position g365G> A was found, with the exchange of the guanine nucleotide by an adenine and consequently the amino acid arginine by a glutamine. It presented the D1 allele with fragments of 335 bp, 148 bp and 122 bp and the D2 allele with 457 bp and 148 bp and with frequencies of 0.43 and 0.57 respectively. The genotypic frequencies found were as follows: D1D1 (22.09%), D1D2 (49.82%), D2D2 (28.09%). After the chi- square test the population presented in Hardy-Weinberg equilibrium. The polymorphism of the pGH / DdeI gene was related to the characteristics of lean meat and pH to 45, properties that are important for the commercialization of fresh meat as well as processed products. KEYWORDS: Assisted selection, SNPs, DdeI, Economic characteristics, Lean meat