Abstract Water deficit stress is the abiotic factor with the highest impact on crop yield. The objective of this study was to evaluate grain yield (GY), the anthesis-silking interval (ASI) and drought tolerance indices in maize hybrids. We evaluated GY and the ASI of 86 hybrids under two moisture levels (normal irrigation and water stress) for three consecutive years. The stress susceptibility index, water stress tolerance, drought resistance coefficient, drought resistance index, stress tolerance index and harmonic mean were evaluated. There were significant hybrid x environment interactions for GY and the ASI. Differences in the ASI among environments ranged from 0 to 5 days. The hybrids P3862, 1I873, 1I923, 1I862 and 1J1211 showed high GY, associated with the highest drought tolerance indices. The stress tolerance index and harmonic mean indices can be used to identify higher-yielding maize hybrids in environments with and without water restriction.

ABSTRACT. Maize breeding programs conduct multi-environment trials every year to assess the performance of new cultivars in pre-releasing tests. The data are combined across sites and seasons to perform a joint analysis in order to obtain information that will help breeders to select the best cultivars for different environments. Beyond this, it is essential to understand the different factors that can hamper the selection and genetic progress (i.e., genetic variability, selection intensity and genotype-by-environment interactions). In this study, the genetic progress (GP) was estimated and the adaptability and stability of 81 maize genotypes were evaluated in a series of trials for the value of cultivation and use (VCU) between the 2010/11 and 2014/15 growing seasons. The genotypes were composed of open-pollinated varieties, topcross hybrids, intervarietal hybrids, and single, double and three-way cross hybrids and were assessed in 117 environments in the central region of Brazil, from which 22 presented environmental stresses. For grain yield, an annual GP of 331.5 kg ha-1 was observed, thus showing efficiency in the selection of superior cultivars. Additionally, it was observed that some low-cost seed cultivars showed yield potential, adaptability and stability estimates that were compatible with commercial hybrids, thus making them quite attractive for cultivation in environments with or without abiotic stresses.

ABSTRACT This study aimed to impute the genetic makeup of individual fishes of Serrasalmidae family on the basis of body weight and morphometric measurements. Eighty-three juveniles, belonging to the genetic groups Pacu, Pirapitinga, Tambaqui, Tambacu, Tambatinga, Patinga, Paqui and Piraqui, were separated into 16 water tanks in a recirculation system, with two tanks per genetic group, where they remained until they reached 495 days of age. They were then weighed and analyzed according to the following morphometric parameters: Standard Length (SL), Head Length (HL), Body Height (BH), and Body Width (BW). The identity of each fish was confirmed with two SNPs and two mitochondrial markers. Two analyses were performed: one for the validating the imputation and another for imputing a genetic composition of animals considered to be advanced hybrids (post F1). In both analyses, we used linear mixed models with a mixture of normal distributions to impute the genetic makeup of the fish based on phenotype. We applied the mixed models method, whereby the environmental effects were estimated by the Empirical Best Linear Unbiased Estimator (EBLUE) and genetic effects are considered random, obtaining the Empirical Best Linear Unbiased Predictor (EBLUP) from the general (GCA) and the specific (SCA) combining ability effects. The results showed that validation of the genetic makeup imputation based on body weight can be used because of the strong correlation between the observed and imputed genotype. The fish classified as advanced hybrids had a genetic composition with a high probability of belonging to known genotypes and there was consistency in genotype imputation according to the different characteristics used.

Este trabalho foi realizado com o objetivo de avaliar os efeitos da aplicação de fungicida, no controle da Cercosporiose e da Mancha-Branca do milho, e suas consequências na produtividade de grãos e na incidência de grãos ardidos, além de estabelecer a relação existente entre a produtividade de grãos e a severidade dessas doenças. Dois experimentos distintos (com Azoxystrobina + Cyproconazole e tratamento controle) foram conduzidos em três locais, no ano agrícola de 2007/2008. Utilizaram-se 12 híbridos comerciais de milho, que foram avaliados em delineamento de blocos casualizados, com três repetições. Foram realizadas cinco avaliações da severidade das doenças Cercosporiose e Mancha-Branca, por meio de escala de notas, variando de 1 (altamente resistente) a 9 (altamente susceptível). Estimou-se a área abaixo da curva de progresso da doença (AACPD). A aplicação de fungicida é eficiente no controle de doenças foliares e na redução da incidência de grãos ardidos, além de proporcionar 12% de aumento na produtividade de grãos, em relação à do tratamento controle. As doenças foliares Cercosporiose e Mancha-Branca reduzem a produtividade de grãos de milho e essa redução é maior quando as doenças ocorrem mais precocemente. A Cercosporiose provoca maior redução na produtividade de grãos, quando comparada com a Mancha-Branca.

This work was carried out in order to evaluate the effects of fungicides on the control of maize gray leaf spot and maize white spot and its implications on the grain yield and rot grain, as well as to establish the relationship between grain yield and disease severity. Twelve commercial single cross hybrids were evaluated in a randomized block design with three repetitions. Five evaluations of disease severity (maize white spot and maize gray leaf spot) were performed using scale-visual symptoms, with scores ranging from 1 (highly resistant) to 9 (highly susceptible). In addition, the area under the disease progress curve (AUDPC) was estimated. Fungicide application is effective in the control of maize leaf diseases, and the experiments without control of the diseases had grain yield lower than that of the experiments with control, with a reduction of 1.2 t.ha-1 (12.3%) on average. The fungicide application had a positive effect in the control of rot grains, with a reduction of 2.6% on average. Maize gray leaf spot and maize white spot reduce the maize grain yield and this reduction is greater when diseases occur earlier. Gray leaf spot causes a greater reduction in grain yield compared with white spot.

A incorporação de resistência genética a doenças e o aumento na produtividade de grãos estão entre os principais objetivos dos programas de desenvolvimento de híbridos. A identificação de locos de caracteres quantitativos (QTL) por meio de análises estatísticas associadas a marcadores moleculares possibilita a rápida obtenção de híbridos resistentes e produtivos. Nesta pesquisa, objetivou-se identificar locos de caracteres quantitativos (QTL) associados com resistência à cercosporiose e com produção de grãos em germoplasma de milho tropical. Foram utilizadas duas linhagens contrastantes em níveis de reação à doença (genótipos pertencentes à GENESEEDS - Ltda), seu híbrido F1 e a população segregante F2. Essas plantas foram fenotipadas quanto à resistência a doença e quanto a produção de grãos e genotipadas com 94 marcadores de microssatélites. A associação dos marcadores ao QTL foi realizada por meio de análises de marcas individuais, utilizando as metodologias de regressão linear e análise da máxima verossimilhança. Observou-se que o tipo de efeito predominante no controle genético da resistência a cercosporiose foi o aditivo e para o controle genético da produção de grãos foi de dominância. Os marcadores microssatélites mais promissores para serem utilizados em estudos de seleção assistida para resistência a cercosporiose são umc2082 na posição 4.03 e umc1117 na posição 4.04 e para produção de grãos, umc1042 e umc1058 nas posições 2.07 e 4.11.

The main objectives of hybrid development programs include incorporating genetic resistance to diseases and increasing grain yield. Identification of Quantitative Trait Loci (QTL) through the statistical analysis of molecular markers allows efficient selection of resistant and productive hybrids. The objective of this research was to identify QTL associated with resistance to gray leaf spot and for grain yield in the germplasm of tropical corn. We used two strains with different degrees of reaction to the disease; the genotypes are owned by GENESEEDS Ltda, their F1 hybrid and the F2 population. The plants were evaluated for gray leaf spot resistance, for grain yield and were genotyped with 94 microsatellite markers. Association of the markers with the QTL was performed by single marker analysis using linear regression and maximum likelihood analysis. It was observed that the additive effect was predominant for genetic control of resistance to gray leaf spot, and the dominant effect in that of grain yield. The most promising markers to be used in studies of assisted selection are: umc2082 in bins 4.03 and umc1117 in bins 4.04 for resistance to gray leaf spot; for grain yield umc1042 in bins 2.07 and umc1058 in bins 4.11.

O objetivo deste trabalho foi identificar genótipos de arroz de terras altas com alta estabilidade e adaptabilidade, pelo método GGE biplot empregando os valores fenotípicos e genotípicos preditos. Foram avaliados 20 genótipos, sendo 14 linhagens desenvolvidas pelo programa cooperativo de melhoramento de arroz de Minas Gerais e seis testemunhas. Verificou-se que a cultivar BRSPepita e MG1097, foram as mais próximas do "genótipo ideal" pela análise GGE Biplot. Em todos os parâmetros comparativos utilizados para comparação do modelo fixo e aleatório (% G+GE, PRESS e correlação), observou-se que o uso das médias fenotípicas apresentou menor potencial preditivo sob desbalanceamento simulado quando comparadas com o uso dos valores genotípicos preditos. Conclui-se que a cultivar BRS Pepita e MG1097 são os genótipos ideais para o sul de Minas Gerais e que a utilização das médias fenotípicas, como base para estudo de estabilidade e adaptabilidade, possui menor poder preditivo quando comparada ao uso das médias genotípicas.

The aim of this study was to identify upland rice genotypes with high stability and adaptability by the GGE biplot method based on the predicted genotypic and phenotypic values. Of the 20 genotypes evaluated, 14 were lines developed by the cooperative program for rice improvement of Minas Gerais and six were controls. The GGE biplot analysis showed that cultivar BRS Pepita and MG1097 were closest to the ideal genotype. In the comparison of the fixed with the random models (% G + GE, prediction error sum of squares and correlation), it was observed that the use of phenotypic means in all comparative parameters indicated a lower predictive potential under simulated imbalance than the use of predicted genotypic values. The conclusion was drawn that BRS Pepita and MG1097 are ideal genotypes for southern Minas Gerais and that the predictive power of the phenotypic means underlying the study of stability and adaptability is lower than of genotypic means.

O objetivo desse trabalho foi avaliar a estabilidade, adaptabilidade e estratificação ambiental, por meio dos métodos AMMI (Additive Main Effects and Multiplicative Interaction Analysis) e GGE (Genotype and Genotypes by Environment Interaction) biplot e comparar a eficiência destes métodos. Utilizaram-se dados da avaliação de vinte híbridos simples experimentais e três comerciais, em onze locais e duas safras, 2005/2006 e 2006/2007. Foram realizadas as análises de variância, adaptabilidade, estabilidade e estratificação ambiental. Os híbridos 10 e 16 apresentaram melhor combinação entre adaptabilidade e estabilidade, considerando os gráficos dos métodos AMMI e GGE biplot respectivamente. A estratificação promoveu uma redução 28% no número de locais. Os métodos AMMI e GGE apresentaram correlação preditiva de 0,88 e 0,86 respectivamente. Pelos resultados obtidos conclui-se que é possível reduzir o número de locais de avaliação; a análise AMMI tendeu ser mais acurada que a análise GGE.

The purpose of this study was to evaluate yield stability, adaptability and environmental stratification by the methods AMMI (Additive Main Effects and Multiplicative Interaction Analysis) and GGE (Genotype and Genotypes by Environment Interaction) biplot and to compare the efficiency of these methods. Data from the evaluation of 20 experimental single-cross and three commercial hybrids and 11 locations, in two growing seasons, 2005/2006 and 2006/2007 were used. Analyses of variance, adaptability, stability and environmental stratification were performed. A better combination of adaptability and stability was observed in the hybrids 10 and 16, according to the graphics of AMMI and GGE biplot methods, respectively. The number of locations could be reduced by 28% based on stratification. The predictive correlation of the AMMI and GGE methods was 0.88 and 0.86, respectively. The results showed that it is possible to reduce the number of evaluation sites; AMMI tended to be more accurate than GGE analysis.

Foram desenvolvidos dois experimentos, um com polinização natural e outro com polinização controlada, em duas localidades do Estado de Minas Gerais (Campo Experimental do Departamento de Biologia da Universidade Federal de Lavras - UFLA e Fazenda Experimental da UFLA, conhecida como "Vitorinha") em 2004/2005, para verificar e quantificar o efeito xênia em milho. Nos dois experimentos, marcadores microssatélites foram utilizados para distinguir grãos de origem cruzada dos resultantes de autopolinização. Para o estudo foram utilizados três híbridos simples, P 30F90, A 2555 e DKB 333 B, realizando todos os cruzamentos possíveis entre eles, incluindo os recíprocos. Nos dois ensaios, avaliaram-se amostras compostas de grãos coletados na região mediana de 10 espigas, tomadas aleatoriamente nas parcelas. Com base nos dados obtidos, por meio de análises de variância e o teste "t" para médias de dados não emparelhados, foi estimado o efeito xênia sobre o peso de grãos individuais e a massa de cem grãos. A utilização dos marcadores microssatélites foi eficiente, sendo possível diferenciar os cruzamentos dos híbridos em todos os arranjos. Conforme os híbridos envolvidos nos cruzamentos e a condição polinizador/receptor de cada um, foram observados efeitos xênia de diferentes magnitudes. Cruzamentos envolvendo 100% de alopólen provocaram aumentos de 7,3% (2,8 g) na massa de cem grãos, comparados com a mistura de 50%, demonstrando a influência da maior pressão de pólen estranho no incremento dessa característica. Em condições de polinização livre, observou-se um efeito médio de 12,6% (variando de 7,4% a 16,5%) no aumento da massa de grãos individuais. Com 100% de pólen estranho, o efeito xênia médio foi de 13,1% na massa de cem grãos e de 8,7% na massa de grãos individuais, tendo ocorrido, todavia, aumentos de 15,4% e 16,6% respectivamente, nessas características, nos cruzamentos mais favoráveis.

Two experiments, with natural and controlled pollination, were carried out at two sites in the State of Minas Gerais (in Experimental area of Biology Department of Universidade Federal de Lavras - UFLA and UFLA farm, known as "Vitorinha") during 2004/2005, in order to verify and quantify the xenia effects in maize. In both experiments microsatellite markers were used to discriminate kernels derived from crosses and from self-pollination, to detect the xenia effect. Three single cross hybrids were used P 30F90, A 2555 and DKB 333 B, and all possible crosses between them were established, including reciprocal ones. In both trials, composite kernels samples taken from the mid-region of 10 randomly collected ears were evaluated. Based on the evaluated obtained data, through analyses of variance and test "t" for means from unpaired data, the xenia effect on the individual grain weight and the weight of 100 kernels was estimated. The use of microsatellite markers could effectively differentiate the crosses from the selfings in both experiments in all possible combinations of the commercial hybrids used. According to the hybrids involved in the crosses, and the condition pollinator/receptor of each one, xenia effects of different magnitudes were observed. Crosses with 100% allopollen resulted in a 7.3% (2.8 g) increase of the weight of 100 grains compared to those with only 50% allopolen, demonstrating an influence of the greater pressure of foreign pollen on the trait increase. In open-pollinated plants, a mean effect of 12.6% (varying from 7.4 to 16.5%) was observed in the increase of individual grain weight. With 100% foreign pollen, the mean xenia effect was 13.1% on the weight of 100 grains and 8.7% on the individual grain weight, while increments of 15.4% and 16.6% in these traits, respectively, were observed in the most favorable crosses.