Diallel and prediction (REML/BLUP) for yield components in intervarietal maize hybrids.

Genetic improvement is essential to achieve increments in maize (Zea mays L.) grain yield components. It may be obtained through crosses, which enable to exploit the effects of intervarietal heterosis, allelic complementarity, as well as gene actions and effects. This study estimated the components of variance and genetic parameters (REML/BLUP) of an intervarietal diallel to select and predict the best genotypes for maize yield components. The experimental design was randomized blocks containing 60 intervarietal maize hybrids arranged in three repetitions. They were obtained through intervarietal crosses and evaluated in a diallel scheme, where 14 open-pollinated varieties were designated as parentals. Thus, 10 crosses were performed for each hybrid combination to obtain the number of seeds necessary for the competition test. The measured traits were: grain volume relative index, the mass of one hundred grains, and grain yield. The male parents and the additive genetic fraction were determinants for grain volume relative index. Mass of one hundred grains and grain yield were defined by the specific combining ability, and female parents revealed low narrow sense heritability. The female parent Taquarão and male parent Argentino Amarelo presented the best general combining abilities for the measured traits. The specific combining abilities were expressed for crosses AL 25 x Dente de Ouro Roxo, AL 25 x BRS Pampeano, and Taquarão x Argentino Branco. Genetic estimates and predictions were consistent and applicable to breeding programs and could be applied in future quantitative genetic studies of maize.

Maternal overnutrition enhances mRNA expression of adipogenic markers and collagen deposition in skeletal muscle of beef cattle fetuses.

Twenty-four pregnant Nellore cows were randomly assigned into 2 feeding level groups (control [CTL]; fed 1.0 times the maintenance requirement; n = 12; and overnourished [ON]; fed at 1.5 times the maintenance requirement; n = 12) to evaluate effects of maternal overnutrition on fetal skeletal muscle development. Cows were slaughtered at 135, 190, and 240 d of gestation and samples of fetal LM were collected for analysis of mRNA expression analysis and for histological evaluation of collagen content and number of muscle cells. There was no interaction between gestational period and maternal nutrition for the variables evaluated (P > 0.05). The mRNA expression of Cadherin-associated protein, ß 1 (ß-catenin) tended to be greater in fetuses from ON cows (P = 0.08), while myogenic differentiation 1 (MyoD; P = 0.56), myogenin (MyoG; P = 0.70), and the number of muscle cells (P = 0.90) were not affected by maternal overnutrition. Gestational period did not affect the mRNA expression of ß-catenin (P = 0.60) and MyoG (P = 0.21). The mRNA expression of MyoD tended to increase with days of gestation (P = 0.06). The mRNA expression of zinc finger protein 423 (Zfp423; P < 0.0001), C/EBPα (P = 0.01), and PPARγ (P < 0.0001) were enhanced in ON fetuses. No effects of days of gestation were observed for mRNA expression of Zfp423 (P = 0.75) and C/EBPα (P = 0.48). The mRNA expression of PPARγ in fetuses at 190 d of gestation tended to be greater than those at 135 and 240 d of gestation (P = 0.06). The mRNA expression of transforming growth factor ß (TGF-ß; P < 0.0001), collagen type III, α I (COL3A1; P < 0.0001), and collagen content (P = 0.01) were increased in ON fetuses. Gestational period did not affect the mRNA expression of collagen type I, α I (COL1A1; P = 0.65). The mRNA expression of COL3A1 (P = 0.09) in fetuses at 190 d of gestation tended to be greater than fetuses at 135 and 240 d of gestation. The mRNA expression of TGF-ß in fetuses at 190 d of gestation was greater than in fetuses at 135 d of gestation (P = 0.03), and the values observed in fetuses at 240 d of gestation did not differ from the other gestational time points. The least value of collagen content (P = 0.01) was observed in fetuses at 135 d of gestation, and no differences were observed among the other gestational time points. These data shows that maternal overnutrition enhances fibrogenesis and likely adipogenesis without compromising myogenesis in fetal skeletal muscle of cattle.