This work aimed to estimate the variance components and genetic parameters, the selection gain, and the cause and effect relationships among traits in order to identify important traits for direct and indirect selection of wheat (Triticum aestivum L.) lines. Three strategies were used to obtain selection gains: direct and indirect selection, an index based on "ranks," and the Smith and Hazel index. In the 2017 crop season in Brazil, 420 wheat lines from the F 5 generation were conducted in families with intercalary controls. High heritability of spike weight, number of kernels, and total kernel weight resulted in the best direct selection gains. The selection of plants with a high number of tillers resulted in grain yield improvement. The use of selection indexes is important in advanced wheat lines; they promote genetic gains distributed among agronomic traits.

Mixed models and multivariate analysis are powerful tools for selecting superior genotypes in plant breeding programs. The BLUP (best linear unbiased prediction) method has been used to predict genetic values without environmental effects. Furthermore, the FAI-BLUP (ideotype-design index) procedure is especially valuable for plant breeding because of multiple-trait selection. This study aimed to determine the genetic potential of advanced wheat generations using REML/BLUP in combination with multivariate techniques for the selection of superior genotypes. The experiment consisted of eleven wheat (Triticum aestivum L.) genotypes. The experimental design was randomized blocks, with three replications. Plant height, spike insertion height, number of tillers, number of spikelets, kernel width, hectoliter weight and kernel weight per plant were determined. The genetic parameters were estimated using the REML/BLUP methodology, and the FAI-BLUP index was calculated using predicted genetic values. The genotypes UFSMFW 1-02, UFSMFW 1-05 and UFSMFW 1-04 show potential to increase the grain yield. The selection gains for number of tillers (14.63 %) and kernel weight per plant (22.35 %) indicate the potential to select superior genotypes.

The aims of this study were to characterize black oat populations by estimating between-and within-populations variance components and genetic parameters, as well as to distinguish the populations using multivariable statistics. The experiment was carried out in randomized blocks design with three repetitions, with 14 black oat populations collected in several municipalities of Rio Grande do Sul state. Agronomic important traits were assessed at physiological maturation stage. Variance components and genetic parameters were estimated considering within-block information. In addition, Mahalanobis distance, relative contribution of traits, and canonical variables were used to distinguish the populations. Selection based on panicle length, number of grains per panicle, panicle weight and panicle grain weight may result in higher selection gains. Panicle grain weight presents a greater contribution to genetic divergence between studied populations. The formation of distinct groups indicated the presence of genetic variability among black oat populations in the northwestern of the Rio Grande do Sul state. Directed crosses between individual plants of populations from (i) Alto Alegre and Salvador das Missões, Chapada, or Santa Rosa or (ii) between plants of populations from Salvador das Missões and Campos Borges or Santa Rosa can generate segregating populations with great genetic variability. The predominance of between-phenotypic variance and a within-genetic variance indicate prospects for success in selection gain and possible selection of a new cultivar with fewer efforts compared to a cross-based method. This is supported by the high values of within-population heritability.

Grain yield is a complex quantitative trait, because its expression is associated to the large number of genes with small effect. In addition, there is interaction among different yield components and environment effect, making difficult the direct selection of genotypes. The most viable alternative for wheat breeding programs, an autogamous plant, is use artificial crosses in order to obtain superior genotypes. Hybridization after use of successive self-fertilizations results in segregating populations, which reveal the genetic variability, especially when the parents are genetically different. Therefore, it is important to know genetic relationships between crosses, which will serve as reference for decision making in the choice of combinations. Therefore, general combining ability (GCA) and specific combining ability (SCA) are used, which facilitate choice of the best parents to compose crossover block. In addition to these parameters, path analysis can be used to determine importance of primary and secondary traits and to guide indirect selection of promising genotypes by means of interest traits.

This study aimed to evaluate direct and indirect effects of agronomic traits importance on grain yield with focus in pre-harvest sprouting. Experiment was conducted in 2017 crop season, and conducted in a randomized block design, with three replications, with eight wheat cultivars (BRS Sábia, CD 105, CD 1104, CD 1440, Frontana, Jadeíte 11, Mirante and ORS Vintecinco). Grain yield and its components were evaluated, as well as other important traits such as pre-harvest sprouting. Data were submitted to variance analysis; and phenotypic, genotypic and environmental correlations were estimated to understand grain yield expression, direct and indirect effects of its components were evaluated through path analysis. Cultivar BRS Sabiá showed shorter cycle, cultivar CD 1104 was highlighted in number of spikes per area, hectoliter weight and grain yield. And cultivars Frontana, CD 1440 and ORS Vintecinco presented the best tolerances pre-harvest sprouting. Grain yield showed high and positive phenotypic and genotypic correlations with number of ears per square meter. Furthermore, high positive direct effect of pre-harvest sprouting on grain yield, revels lower tolerance for cultivars with high grain yield. Number of spikes per square meter showed intermediate and positive direct effect and pre-harvest sprouting had the greatest direct effect on grain yield.