ABSTRACT. We examined whether single-nucleotide polymorphisms (SNPs) in the calpain (CAPN) and calpastatin (CAST) genes, described from Bos primigenius taurus, are polymorphic in Nellore cattle. We also looked for a possible association of linkage disequilibrium of this polymorphism with tenderness of the longissimus dorsi muscle after 7, 14 and 21 days of postmortem aging in 638 purebred Nellore bulls. Meat tenderness was measured as Warner-Bratzler shear force. Additive and dominance effects were tested for SNPs of the three genotypic classes; the substitution effect was tested for SNPs with missing genotypic classes. Genotypic and gene frequencies were also calculated for the different SNPs. An increase in tenderness was observed from 7 to 21 days; the average values for shear force at 7, 14 and 21 days of aging were 5.92 ± 0.06, 4.92 ± 0.05, and 4.38 ± 0.04 kg, respectively. All markers showed polymorphism, but there was no CC genotype for CAPN316, and few animals showed the AA genotype for CAPN530. The alleles CAPN4751, UOGCAST1, and WSUCAST were found to have additive and dominance effects for shear force at 7, 14 and 21 days, while CAPN316 showed a substitution effect for shear force at

Special hard endosperm maize (Zea mays L.) adapted for optimum dry milling yields is produced worldwide. Argentine flint maize is internationally known, and specific values for grain vitreousness, floaters, and test weight are demanded by the industry. Agricultural practices aimed to reach these standards, however, are not clear for farmers. Our general objective was to identify possible management options for maximizing the grain quality attributes described by these standards. We tested two flint and two dent kernel type genotypes under contrasting management options and environmental conditions (stand density, N fertilizer, defoliations, years), and studied their yield and grain quality response. Flint genotypes yielded less than dents across all tested field treatments (flint vs. dent, P ≤ 0.001), with larger differences at the lowest yielding conditions. Large differences between kernel types, and for genotypes within each kernel type, were evident for all grain quality traits (test weight, floaters, vitreousness, 8 mm screen retention) and composition (protein, oil, starch). Low N fertilization levels and stressful situations during grain filling where the treatments reducing grain hardness and screen retention the most, especially for some genotypes. Other than genotype selection, adequate N availability and low stand density helped improve test weight, vitreousness, floaters, and screen retention, all traits relevant for maize dry milling industry.Core Ideas Crop management options for maximizing maize kernel hardness are mostly unknown. Flint genotypes always yielded less than dented ones across a wide range of field treatment combinations. Stand density, N fertilization, and genotype selection are key management options for optimum grain quality.

The association between two single nucleotide polymorphisms (SNPs), T945M and UCP1SNP1, with hot carcass weight (HCW, kg, N = 618), longissimus dorsi muscle area (REA, cm(2), N = 633), and backfat thickness (BF, mm, N = 625), measured in Nellore cattle in Brazil, was evaluated. Likelihood ratio tests were used to evaluate reduced (fixed effects of general mean, contemporary group, yearling weight, age at slaughter, and random effect of infinitesimal genetic value) and full model (reduced model effects plus quantitative trait locus effects). Additive and dominance effects were tested for each SNP. Genotypic and gene frequencies were also obtained for the SNPs and a descriptive phenotype analysis was made. Mean values for HCW, REA and BF were equal to 288.13 +/- 0.55 kg, 73.14 +/- 0.27 cm(2), and 4.28 +/- 0.07 mm, respectively; the coefficients of variation were 4.74, 9.24, and 42.43%, respectively. Gene frequencies for T945M and UCP1SNP1 were f(C) = 0.89, f(T) = 0.11, f(C) = 0.81, and f(G) = 0.19. The SNP T945M had a genotypic frequency of only three animals for TT genotype. Additive effects were observed for T945M on REA and BF, while UCP1SNP1 affected HCW and BF. Based on the significant additive effects of the SNPs and the gene frequencies that we found, we can expect genetic gains with marker assisted selection.

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