Genotypic correlation and path analysis in early and super-early maize genotypes.

The aims of this study were to assess the linear relationships between agronomic and nutritional traits and to identify promising traits for indirect selection in early and super-early maturing maize genotypes. Two trials were run in the 2009/2010 agricultural year, each consisting of a randomized block design with three replications. One trial was run on 36 early maturing maize genotypes and the other on 22 super-early maturing genotypes. Six agronomic traits, 11 protein-nutritional traits, and four energetic-nutritional traits were measured. Error normality assumptions were verified using the Kolmogorov-Smirnov test and residual variance homogeneity assumptions using the Levene test. Analysis of variance and the F-test were run for each of the 21 traits. Next, the genotype correlation coefficient matrix was estimated for the 21 traits and each trial. Ridge path analysis was based on values of k = 0.00 and k = 0.10 on the diagonal of X'X correlation matrix, taking the nutritional traits as principal variables and agronomic traits as explanatory variables. The number of days from sowing to male flowering, the number of days from sowing to female flowering, plant height, ear insertion height, ear weight and grain yield can be used in indirect selection as indicators of grain nutritional quality.

Genetic progress in homogeneous regions of wheat cultivation in Rio Grande do Sul State, Brazil.

The State of Rio Grande do Sul (RS) stands out as the largest wheat producer in Brazil. Wheat is the most emphasized winter cereal in RS, attracting public and private investments directed to wheat genetic breeding. The study of genetic progress should be performed routinely at breeding programs to study the behavior of cultivars developed for homogeneous regions of cultivation. The objectives of this study were: 1) to evaluate the genetic progress of wheat grain yield in RS; 2) to evaluate the influence of cultivar competition trial stratification in homogeneous regions of cultivation on the study of genetic progress. Grain yield data of 122 wheat cultivars evaluated in 137 trials arranged in randomized block design with three or four replications were used. Field trials were carried out in 23 locations in RS divided into two homogeneous regions during the period from 2002 to 2013. Genetic progress for RS and homogeneous regions was studied utilizing the method proposed by Vencovsky. Annual genetic progress for wheat grain yield during the period of 12 years in the State of RS was 2.86%, oscillating between homogeneous regions of cultivation. The difference of annual genetic progress in region 1 (1.82%) in relation to region 2 (4.38%) justifies the study of genetic progress by homogeneous regions of cultivation.

Direct effects on scenarios and types of path analyses in corn hybrids.

The objective of this study was to estimate the direct effects of explanatory variables on the grain yield of corn in the combinations formed by three types of hybrids x two harvests x nine scenarios of explanatory variables x two types of path analyses. Eleven explanatory variables were measured in 361, 373, and 416 single-, triple-, and double-cross hybrid plants from the 2008/2009 harvest, respectively, and in 1777, 1693, and 1720 single-, triple-, and double-cross hybrid plants from the 2009/2010 harvest, respectively: plant height at harvest (PH), ear insertion height (EIH), ear weight (EW), number of grain rows per ear (NR), ear length (EL), ear diameter (ED), cob weight (CW), cob diameter (CD), 100-grain mass (HGM), number of grains per ear (NGE), grain length (GL) and, the main variable, grain yield (YIELD). Before conducting the traditional and ridge path analyses, 0, 1, 2, 3, 4, 5, 6, 7, and 8 explanatory variables were excluded from scenarios 1, 2, 3, 4, 5, 6, 7, 8, and 9, respectively. Next, the direct effects of explanatory variables on YIELD were estimated for each hybrid, harvest, scenario, and type of path analysis. The variables EW, NGE, and HGM had stronger direct effects on YIELD in the first three scenarios and the variables EL and ED had stronger direct effects on YIELD in the other scenarios regardless of hybrid or harvest. The use of the ninth scenario of path analysis is recommended regardless of hybrid and harvest given the ease of explanatory variable measurement (EIH, EL, and ED), the low degree of multicollinearity and the good prediction of the path analysis (R2 ≥ 0.78).

Multicollinearity in canonical correlation analysis in maize.

The objective of this study was to evaluate the effects of multicollinearity under two methods of canonical correlation analysis (with and without elimination of variables) in maize (Zea mays L.) crop. Seventy-six maize genotypes were evaluated in three experiments, conducted in a randomized block design with three replications, during the 2009/2010 crop season. Eleven agronomic variables (number of days from sowing until female flowering, number of days from sowing until male flowering, plant height, ear insertion height, ear placement, number of plants, number of ears, ear index, ear weight, grain yield, and one thousand grain weight), 12 protein-nutritional variables (crude protein, lysine, methionine, cysteine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine, and arginine), and 6 energetic-nutritional variables (apparent metabolizable energy, apparent metabolizable energy corrected for nitrogen, ether extract, crude fiber, starch, and amylose) were measured. A phenotypic correlation matrix was first generated among the 29 variables for each of the experiments. A multicollinearity diagnosis was later performed within each group of variables using methodologies such as variance inflation factor and condition number. Canonical correlation analysis was then performed, with and without the elimination of variables, among groups of agronomic and protein-nutritional, and agronomic and energetic-nutritional variables. The canonical correlation analysis in the presence of multicollinearity (without elimination of variables) overestimates the variability of canonical coefficients. The elimination of variables is an efficient method to circumvent multicollinearity in canonical correlation analysis.

Sample size for estimation of direct effects in path analysis of corn.

The objective of this study was to assess the sample size required for estimating the direct effects of explanatory variables on the grain yield of corn in the combinations formed by three types of hybrids x two harvests x nine scenarios of explanatory variables x two types of path analyses x four levels of accuracy. A total of 6340 plants were evaluated (361, 373, and 416 plants from single-, triple-, and double-cross hybrids in the 2008/2009 harvest, respectively, and 1777, 1693, and 1720 plants from single-, triple-, and double-cross hybrids in the 2009/2010 harvest, respectively). Eleven explanatory variables were measured in each plant: plant height, ear insertion height, ear weight, number of grain rows per ear, ear length and diameter, cob weight and diameter, 100-grain mass, number of grains per ear, grain length and, the main variable, grain yield. Thus, nine scenarios were planned (scenarios 1, 2, 3, 4, 5, 6, 7, 8, and 9 with 0, 1, 2, 3, 4, 5, 6, 7, and 8 explanatory variables excluded, respectively) and two types of path analyses conducted (traditional and ridge path analyses). The sample size required for estimating the direct effect of each explanatory variable on grain yield was assessed using resampling with replacement at four accuracy levels [95% confidence interval ranges (95%CI) of 0.15, 0.25, 0.35, and 0.45]. The use of the ninth scenario of path analysis is recommended regardless of hybrid and harvest given the smaller sample size required compared to the previous scenarios. To estimate direct effects with the maximum 95%CI of 0.25, 10 to 530 plants are required depending on the type of hybrid, harvest, scenario, type of path analyses, and explanatory variables. To estimate the direct effects in the ninth scenario with a maximum 95%CI of 0.25, 120 plants suffice regardless of the type of hybrid, harvest, or type of path analyses.

Genetic progress in sunflower crop in Rio Grande do Sul State, Brazil.

The sunflower has adaptability to growing regions with different climatic and soil characteristics, showing drought tolerance and high-quality oil production. The State of Rio Grande do Sul is the third largest sunflower producer in Brazil, with research related to the sunflower breeding initiated after the decade of 1950. The aim of this study was to evaluate the genetic progress for grain yield, oil content, and oil yield of sunflower (Helianthus annuus L.) in the State of Rio Grande do Sul. Data of grain yield, oil content, and oil yield obtained from 58 sunflower cultivar yield trials in 19 municipalities in Rio Grande do Sul during the period from 2005 to 2014 were used. Genetic progress was studied according to the methodology proposed by Vencovsky and data from sunflower cultivar yield trials were used. Annual genetic progress of sunflower during the period of 10 years (2005-2014) was 132.46 kg⋅ha-1⋅year-1 for grain yield, -0.17%/year for oil content, and 48.11 kg⋅ha-1⋅year-1 for oil yield. The sunflower-breeding programs in the State of Rio Grande do Sul were efficient for the traits grain yield and oil yield and presented no efficiency for oil content.

Genetic progress in oat associated with fungicide use in Rio Grande do Sul, Brazil.

The State of Rio Grande do Sul (RS) is the largest producer of oat in Brazil with the aid of consolidated breeding programs, which are constantly releasing new cultivars. The main objectives of this study were to: 1) evaluate the annual genetic progress in grain yield and hectoliter weight of the oat cultivars in RS, with and without fungicide use on aerial parts of plants; and 2) evaluate the efficiency of oat breeding programs in introducing disease-resistant genes in the released cultivars through network yield trials conducted with and without fungicide use on aerial plant parts. The data on grain yield and hectoliter weight were obtained from 89 competition field trials of oat cultivars carried out from 2007 to 2014 in nine municipalities of RS. Of the total 89 trials, 44 were carried out with fungicide application on aerial plant parts and 45 were carried out without fungicide application. The annual genetic progress in oat cultivars was studied using the methodology proposed by Vencovsky (1988). The annual genetic progress in oat grain yield was 1.02% with fungicide use and 4.02% without fungicide use during the eight-year study period in RS. The annual genetic progress with respect to the hectoliter weight was 0.08% for trials with fungicide use and 0.71% for trials without fungicide use. Performing network yield trials with and without fungicide use on the aerial plants parts is a feasible method to evaluate the efficiency of oat breeding programs in introducing disease-resistant genes in the released cultivars.

Sample sizes to estimate mean values for tassel traits in maize genotypes.

Tassel traits are important in maize breeding programs aiming to reduce the size and number of branches and maintain satisfactory pollen production in order to increase grain yield. The objectives of this study were to determine the sample size (number of tassels) required to estimate the mean values for tassel traits in maize genotypes and to verify the variability of sample size among genotypes. Twenty maize genotypes were evaluated in an experiment carried out in a randomized block design with three replicates. Twenty tassels were randomly collected in each plot, for a total of 1200 tassels. In each tassel, the following traits were measured: peduncle dry matter, branching space dry matter, central spike dry matter, tassel dry matter, peduncle length, branching space length, central spike length, tassel length, tassel dry matter to tassel length ratio, number of primary branches, number of secondary branches, and tassel branch number. Measures of central tendency and variability were calculated, analysis of variance and mean comparison tests were performed, normality was verified, and the sample size was determined. In order to estimate the means with the same precision, the sample size for weight traits was greater than that for length traits. For tassel traits, 11, 20, and 43 tassels are sufficient to estimate the mean with a precision of 40, 30, and 20%, respectively, of the estimated mean at a 95% confidence level. These data show that there is sample size variability among maize genotypes.

Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) preying on Microtheca spp. (Coleoptera: Chrysomelidae) larvae.

Microtheca spp. (Coleoptera: Chrysomelidae) are insect pests primarily related to Brassicaceae crops. In the State of Rio Grande do Sul (RS), southern Brazil, they are found on forage turnip, Raphanus sativus L. var. oleiferus Metzg., which is commonly grown during fall/winter seasons. This work reports the predation of Microtheca spp. larvae by Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) larvae, on forage turnip crop, in Santa Maria, RS. This register provides new information about Microtheca spp. natural enemies in Brazil, which might be a new option for integrate pest management of these species.

Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) preying on Microtheca spp. (Coleoptera: Chrysomelidae) larvae / Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) predando larvas de Microtheca spp. (Coleoptera: Chrysomelidae)

Microtheca spp. (Coleoptera: Chrysomelidae) are insect pests primarily related to Brassicaceae crops. In the State of Rio Grande do Sul (RS), southern Brazil, they are found on forage turnip, Raphanus sativus L. var. oleiferus Metzg., which is commonly grown during fall/winter seasons. This work reports the predation of Microtheca spp. larvae by Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) larvae, on forage turnip crop, in Santa Maria, RS. This register provides new information about Microtheca spp. natural enemies in Brazil, which might be a new option for integrate pest management of these species.

Microtheca spp. (Coleoptera: Chrysomelidae) são insetos-praga relacionados principalmente às culturas da família Brassicaceae. No Estado do Rio Grande do Sul (RS), no sul do Brasil, são encontrados no nabo forrageiro, Raphanus sativus L. var. oleiferus Metzg, comumente cultivado no outono/inverno. Este trabalho relata a predação de larvas de Microtheca spp. por larvas de Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae), em nabo forrageiro, em Santa Maria, RS. Este registro oferece nova informação sobre os inimigos naturais de Microtheca spp. no Brasil os quais podem ser uma nova opção para o manejo integrado dessas espécies.