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The primary objective of soybean-breeding programs is to develop cultivars that offer both high grain yield and a maturity cycle tailored to the specific soil and climatic conditions of their cultivation. Therefore, predicting the genetic value is essential for selecting and advancing promising genotypes. Among the various analytical approaches available, deep machine learning emerges as a promising choice due to its capability to predict the genetic component of phenotypes assessed under field conditions, thereby enhancing the precision of breeding decisions. This study aimed to determine the efficiency of artificial neural networks (ANNs) in predicting the genetic values of soybean genotypes belonging to populations derived from crosses between parents of different relative maturity groups (RMGs). We characterized populations with broad and restricted genetic bases for RMG traits. Data from three soybean populations, evaluated over three different agricultural years, were used. Genetic values were predicted using the multilayer perceptron (MLP) artificial neural network and compared to those obtained using the best unbiased linear prediction from variance components using restricted maximum likelihood (RR-BLUP). The MLP neural network efficiently predicted genetic values for the relative maturity group trait for genotypes belonging to populations of broad and restricted crosses, with an R2 of 0.999 and root-mean-square error (RMSE) of 0.241, and for grain yield, there was an R2 of 0.999 and an RMSE of 0.076. While the percentage of coincident superior genotypes remained relatively consistent, a significant difference was observed in their ranking order. The genetic gain with selection estimated using MLP was higher by 30–110% compared to RR-BLUP for the relative maturity group trait and 90–500% for grain yield. Artificial neural networks (ANNs) showed higher efficiency than RR-BLUP in predicting the genetic values of the soybean population. Local selection at intermediate latitudes is conducive to developing lines adaptable for regions at higher and lower latitudes.

Soybean has a recognized narrow genetic base that often makes it difficult to visualize available genetic and phenotypic variability and identify superior genotypes during the selection process. However, the phenotypic expression of soybean plants is highly affected by photoperiod and the cultivation of a given variety is performed in the latitude range that presents ideal conditions for its development based on its relative maturity group (RMG) for the optimization of the phenotypic expression of its genotype. Based on the above, this study aimed to evaluate the efficiency of artificial neural networks (ANNs) as a tool for the correct discrimination and classification of tropical soybean genotypes according to their relative maturity group during the population selection process with the aim of optimizing the phenotypic performance of these selected genotypes. For this purpose, three biparental populations were synthesized, one with a wide genetic variability for the RMG character obtained from the hybridization between genitors of maturity groups RMG 5 (Sub-tropical 23° LS) × RMG 9.4 (Tropical 0° LS) and two populations with a narrow variability obtained between genitors RMG 7.3 (Tropical 20° LS) × RMG 9.4 and RMG 5.3 × RMG 6.7, respectively. Criteria for comparing the developed ANN architecture with Fisher’s linear and Anderson’s quadratic parametric discriminant methodologies were applied to the data for the discrimination and classification of the genotypes. ANN showed an apparent error rate of less than 8.16% as well as a low influence of environmental factors, correctly classifying the genotypes in the populations even in cases of reduced genetic variability such as in the RMG 5 × RMG 6 population. In contrast, the discriminant functions were inefficient in correctly classifying the genotypes in the populations with genealogical similarity (RMG 5 × RMG 6) and wide genetic variability, with an error rate of more than 50%. Based on the results of this study, ANN can be used for the discrimination of genotypes in the initial generations of selection in breeding programs for the development of high performance cultivars for wide and reduced photoperiod amplitudes, even with fewer selection environments, more efficiently, and with fewer time and resources applied. As a result of similarity between the parents, ANN can correctly classify genotypes from populations with a narrow genetic base, in addition to pure lines and genotypes with a high degree of inbreeding.

Com o objetivo de avaliar o desempenho de genótipos de milho-pipoca no Planalto Norte de Santa Catarina, foram realizados experimentos na Epagri/Estação Experimental de Canoinhas, nas safras 2003/04 e 2004/05. Foram avaliados 15 genótipos no primeiro experimento e dez no segundo experimento. Observou-se variação entre os genótipos quanto às características de ciclo, porte, quebra de colmos, produtividade e capacidade de expansão. Os híbridos IAC 112 e IAC 125 apresentaram elevado potencial de produção de grãos e boa capacidade de expansão dos grãos.

The efficient use of genetic resources- stored in germplasm collections can be maximized if morphoagronomic and molecular information on the accessions is made available. To achieve this, a collection that is well-structured, well-curated and easily accessible (the core collection) is required. Consequently, the objective of the current study was to characterize 80 landrace accessions from the maize core collection of the Federal University of Viçosa (UFV), and assay thenngenetic diversity of the various landraces, considering grain type and ecogeographic origin. For this, AFLP analysis was performed using 12 primer combinations. Genetic diversity of the collection was quantified with the UPGMA method, using the Jaccard Index to quantify dissimilarity. The core collection was divided into four sub-populations by grain type, and into six sub-populations based on ecogeographic origin. Genetic diversity analysis was performed both within and between sub-populations. A high level of genetic variability was found among the landrace accessions of UFV Core Collection, principally among those accessions with dentate type grains.Classification by grain type and ecogeographic origin allowed genetically divergent groups to be distinguished.

Sorghum [Sorghum bicolor (L.) Moench] crop is distinguished from other crops for its tolerance to both water deficit and excess soil moisture, under very dry and/or very hot environmental situations in which the productivity of other cereals becomes uneconomical. This work was conducted to evaluate the effects of irrigation on root conformation at the initial development phase of sweet sorghum. So, BRS 501 cv. was subjected to four irrigation levels based on 80%, 60%, 40% and 20% of the field capacity (CC). The decreased availability of water in the soil negatively affected the majority of the characteristics under evaluation except for the relationship between the root system and the aerial part (SR/PA), average root diameter (DMR) and specific root area (ARE). We concluded that the growth of sweet sorghum plants under evaluation is sensible to the decrease of water in the soil, as it is affected by low water availability. This methodology, common to other crops, can be used for saccharine sorghum in order to establish hydric availabilities in new experiments to discriminate the drought-tolerant cultivars.

This study was conducted to identify the sweetsorghum cultivars presenting higher tolerance todrought as well as to phenotypically discriminatethe root morphological characteristics of thosegenotypes for environments with water deficit.The cultivars (Rio, Ramada, BRS 501 andBRS 506) were subjected to two treatments(Environments). The first one was an environmentnamed unrestricted water (AI) -37.5 kPa, andthe second one, with hydric restriction, namedrestricted water (AR) with a matrix pressurelower than the with CPA treatment, that is, -375kPa. The difference between the ideal weight ofthe treatment and the weight observed in thevase, before being irrigated, when compared withan identical vase used in the treatments withoutthe plant, provided an evapotranspiration ofthe cultivar during the period. The roots wereanalyzed by the WinRhizo system, in orderto obtain the following characteristics understudy: length, volume, superficial area, projectedarea and root diameter. For all characteristicsunder evaluation, the variance analysis showedno interaction (P> 0.05) between genotypeand environment. Separately, no variationswere observed (P> 0.05) in the genotypes and environments evaluated for the characteristicsunder study, except the root diameter. Thus,it was observed that the diameter of the rootswere higher (P

Objetivou-se com este trabalho comparar o sistema de produção de milho, recomendado nos anos 40, com o atualmente empregado. Para isso, utilizou-se como base o artigo publicado por Antônio Secundino de São José, na Revista Ceres, em 1944, comparando-se as práticas agrícolas recomendadas para a cultura do milho na época com as atualmente empregadas. Naquela época, não havia preocupação direta com os aspectos conservacionistas de solo e água. Todavia, iniciava-se o processo de elevação da produtividade de grãos, com base no uso de mais insumos, todos obtidos na propriedade, como o esterco bovino, e de obtenção das próprias sementes. A cultura do milho era tratada de maneira individualizada, sem os conceitos de integração de lavoura, pecuária e conservação de solo e água. Atualmente, muitos conceitos recomendados há 70 anos ainda são utilizados na agricultura orgânica e familiar. Por outro lado, no cultivo em grande escala da cultura do milho utilizam-se os mais variados insumos, como fertilizantes sintéticos, herbicidas, inseticidas, sementes de híbridos (com ou sem eventos transgênicos), aplicação de fungicidas, plantio e colheita mecanizados. Conclui-se que nos últimos 70 anos ocorreram muitas mudanças no sistema de produção de milho e que estas mudanças foram fundamentais para que a produtividade aumentasse 3,79 vezes no período analisado. Todo o sistema de produção foi modificado em relação aos fatores de construção e proteção da produtividade, que por sua vez, deram suporte para que o Brasil chegasse a posição de terceiro maior produtor e exportador de milho do mundo, saltando de 5,6 milhões de toneladas em 1944 para 81,5 milhões de toneladas em 2013.

O sorgo [Sorghum bicolor (L.) Moench] é uma planta de origem africana, da mesma família do milho. O sorgo tipo sacarino é utilizado como matéria prima para bionergia (etanol) e apresenta elevada eficiência no uso da água. Este trabalho teve como objetivo caracterizar cultivares de sorgo sacarino quanto às características fisiológicas em diferentes intensidades de irrigação, analisar trocas gasosas e fluorescência de clorofila a fim de subsidiar programas de melhoramento genético direcionados à obtenção de genótipos produtivos de sorgo em situações de déficit hídrico. Foram avaliados quatro cultivares, tolerantes à seca: Rio, Ramada, BRS 501, BRS 506. O tratamento consistiu de três disponibilidades de água no solo: 80%, 60% e 40% da capacidade de campo (c.c.). Foram avaliadas a condutância estomática (gs), a taxa de fotossíntese líquida (A), a transpiração foliar (E) e a eficiência intrínseca do uso da água (EIUA, A/gs). Também foi determinada a eficiência quântica ideal (Fv/Fm) do fotossistema II (FSII), o rendimento quântico basal dos processos fotoquímicos no FSII (Fo/Fm) e a eficiência fotoquímica no FSII (Fv/Fo). A disponibilidade hídrica não causou alteração (P > 0,05) na transpiração dos cultivares Ramada e BRS 501, mas afetou (P < 0,05) os cultivares Rio e BRS 506 que responderam positivamente ao aumento da irrigação. Resultado semelhante ocorreu com a fotossíntese, já que as diferentes disponibilidades hídricas influenciaram positivamente apenas os cultivares Rio e BRS 506. Com o incremento da irrigação houve um acréscimo (P < 0,05) na condutância estomática dos cultivares avaliados. Os resultados referentes à fluorescência da clorofila mostraram superioridade dos cultivares BRS 506, Rio e Ramada com valores maiores (P < 0,05) de Fv/Fm e Fv/Fo. Os distintos níveis de disponibilidade hídrica e os diferentes cultivares não promoveram (P > 0,05) alteração na EIUA. Esta metodologia, comum às outras culturas, pode ser utilizada para sorgo sacarino para estabelecer disponibilidades hídricas em novos experimentos que tenham a finalidade de discriminar cultivares tolerantes à seca.

n plant breeding programs that aim to obtain cultivars with nitrogen (N) use efficiency, the focus is on methods of selection and experimental procedures that present low cost, fast response, high repeatability, and can be applied to a large number of cultivars. Thus, the objectives of this study were to classify maize cultivars regarding their use efficiency and response to N in a breeding program, and to validate the methodology with contrasting doses of the nutrient. The experimental design was a randomized block with the treatments arranged in a split-plot scheme with three replicates and five N doses (0, 30, 60, 120 and 200 kg ha-1) in the plots, and six cultivars in subplots. We compared a method examining the efficiency and response (ER) with two contrasting doses of N. After that, the analysis of variance, mean comparison and regression analysis were performed. In conclusion, the method of the use efficiency and response based on two N levels classifies the cultivars in the same way as the regression analysis, and it is appropriate in plant breeding routine. Thus, it is necessary to identify the levels of N required to discriminate maize cultivars in conditions of low and high N availability in plant breeding programs that aim to obtain efficient and responsive cultivars. Moreover, the analysis of the interaction genotype x environment at experiments with contrasting doses is always required, even when the interaction is not significant.

O objetivo desse estudo foi investigar o emprego dos componentes da eficiência no uso de nitrogênio e das atividades das enzimas nitrato redutase e glutamina sintetase na seleção de genótipos de milho eficientes no uso de nitrogênio (N). Foram avaliados 10 genótipos de milho em estádio de V4 em condições de alto e baixo N. O experimento foi composto por um fatorial 2 x 10 (dois níveis de N e 10 genótipos de milho) em delineamento inteiramente casualizados com três repetições. Os seguintes caracteres foram avaliados: as eficiências na absorção (EAbN), na utilização (EUtN) e no uso de N (EUsN) e as atividades das enzimas glutamina sintetase (GS) e nitrato redutase (NR). Para os caracteres que o efeito de genótipos foi significativo (pThe aim of this study was to investigate the employment of components of the nitrogen efficiency use (NUE), and of the activities of the nitrate reductase and glutamine synthetase enzymes in the selection of nitrogen use efficient maize genotypes of maize. Ten maize genotypes at V4 stage were evaluated under high and low N. The experiment consisted of a 2 x 10 factorial (two levels of N and ten maize genotypes), in a randomized complete block design with three replicates. The following traits were evaluated: N uptake efficiency (NUpE), N utilization efficiency (NUtE) and N use efficiency (NUE), and activities of the glutamine synthetase (GS) and nitrate reductase (NR) enzymes. For traits which the effect of genotype was significant (p

The objective of this study was to determine the relationship between heterosis and genetic divergence for phosphorus use efficiency (PUE) in tropical maize. It was used two groups of genitors, each consisting of seven lines, contrasting with each other in the nitrogen and phosphorus use efficiency. It was obtained 41 hybrid combinations between these groups, which were evaluated in low phosphorus. Randomized complete block design with two replications was used. For obtaining the components of variance and the breeding values were used REML/BLUP method. In the genotyping of the parental lines were used 80 microsatellite markers. Through the correlation between genetic distance obtained by the markers and specific combining ability it was not possible to determine with accuracy by molecular markers, the crosses that produced hybrids with the highest heterosis for PUE. Thus, is possible to conclude that there is no relationship between genetic divergence and heterosis for phosphorus use efficiency and its components in tropical maize.O objetivo deste estudo foi determinar a relação entre divergência genética e heterose para a eficiência no uso de fósforo (EUP) em milho tropical. Utilizaram-se dois grupos de genitores, compostos de sete linhagens cada, contrastantes entre si para as eficiências no uso de nitrogênio e fósforo. Foram obtidas 41 combinações híbridas entre esses grupos, as quais foram avaliadas em baixo fósforo. Usou-se o delineamento em blocos ao acaso com duas repetições. A obtenção dos componentes de variância e valores genéticos foi realizada via REML/BLUP e, para genotipagem das linhagens genitoras, foram utilizados 80 marcadores microssatélites. Através da correlação entre a distância genética obtida pelos marcadores e a capacidade específica de combinação, observou-se não ser possível a determinação com acurácia, via marcadores moleculares, dos cruzamentos que produziram os híbridos com as maiores heteroses para EUP. Com isso, é possível concluir que não há relação entre divergência genética e heterose para eficiência no uso de fósforo e seus componentes em milho tropical.

Os objetivos deste trabalho foram verificar a acurácia do método da Seleção Genômica Ampla (GWS) no melhoramento de milho nas condições de estresse nutricional e propor novos métodos de melhoramento baseados em GWS. Foram estimados os dois componentes da eficiência no uso de nitrogênio e de fósforo (eficiência de absorção e de utilização) em 41 combinações híbridas, em dois experimentos, sob baixa e alta disponibilidades de N e P. Para a genotipagem da população de estimação, foram utilizados 80 marcadores microssatélites. As estimativas dos parâmetros genéticos foram obtidas via REML/BLUP, e a predição dos valores genéticos genômicos, via regressão aleatória (Random Regression - RR) aplicada à seleção genômica ampla (RR-BLUP/GWS). Para os caracteres em que a GWS apresentou altos valores de acurácia, essa foi comparada com os métodos de Seleção Recorrente Intra e Interpopulacional. Com o uso da GWS houve aumento significativo na acurácia seletiva e nos ganhos genéticos por unidade de tempo.The objectives of this work were to verify the accuracy of the Genome Wide Selection method (GWS) in the maize breeding for nutritional stress conditions and propose new breeding methods based on GWS. The efficiency of two components of use of nitrogen and phosphorus (absorption and utilization) was estimated in 41 single-cross hybrids assessed in two experiments under low and high availability of N and P. Eighty microsatellite markers were used to genotype the base population. The estimates of genetic parameters were obtained by REML/BLUP and the predictions of genetic genomic values were obtained by random regression (RR), applied to genome wide selection (RR-BLUP/GWS). GWS showed high values of accuracy for the traits; it was comparable to the methods of Recurrent Intra and Interpopulational Selection. It was concluded that there is a significant increase in selective accuracy and in the genetic gains per unit of time with use of GWS.

Molybdenum applications and nitrogen fertilization at different times may interfere with enzymaticactivity in maize (Zea mays L.) plants. The aim of this work was evaluate the effect of nitrogen fertilization andmolybdenum application on the activity of the enzyme nitrate reductase (NR), nitrogen content and grain yield intwo maize cultivars. A randomized blocks experimental design was used, in a 3 x 2 x 2 + 2 factorial scheme withfour replications and 50.000 plants ha-1. The following parameters were evaluated: enzymatic activity depending onthe harvest season, leaf nitrogen content and grain yield. The time of nitrogen application affected enzymatic activityindependent of fertilization with molybdenum. The highest grain yield and increased enzymatic activity were obtainedby applying nitrogen at the four expanded leaves stage. The growing seasons of corn cultivars may affect the enzymeactivity.

This study had three objectives: i) to observe maize inbred lines response to nitrogen (N) and phosphorus (P) acquisition as well as their utilization efficiencies and traits of root morphology in contrasting levels of these nutrients, ii) to study the relationship between root morphology and nutrient use efficiencies for both nutrients, and iii) to identify contrasting parents with components N and P use efficiency for an inheritance study. We evaluated 15 inbred lines in two experiments conducted in contrasting conditions of N and P. We evaluated the shoot, root traits and nutritional efficiencies and observed the genetic variability for most traits. Selection can be practiced for most of these traits in specific environments. Under conditions of nutritional stress, average and heritability estimates were of lesser magnitude. In this study, the shoot and root morphology traits were shown to be associated with the acquisition efficiency of both N and P in all of the environments that were evaluated.

The objective of this study was to evaluate four maize testers for identification of superior inbreed lines in testcross. The four testers evaluated are cultivars with narrow or wide genetic base (single-cross hybrids and open pollinated varieties) and two kernel types (flint or dent). SynD and SynF testers are open pollinated varieties with dent and flint kernels, respectively, and FSH and DSH testers are single-cross hybrids with flint and dent kernels, respectively. SynD tester showed the biggest genetic variance among the maize inbreed lines in crosses. The effects of general combining ability (GCA) for lines and specific combining ability (SCA) for lines x testers were significant, whereas GCA effects for testers were not significant. SynD and SynF testers identified the largest number of lines with higher GCA. The DSH and FSH testers showed suitable to identify lines with high SCA. It was concluded that SynD and SynF testers are adequate to identify inbreed lines with high GCA effects, and it's possible to identify new lines with high heterotic potential in each one of the four testers.O objetivo deste estudo foi avaliar quatro testadores de milho quanto à capacidade de identificar linhagens superiores em testcross. Os quatro testadores avaliados são cultivares com base genética ampla (variedades de polinização aberta) e estreita (híbridos simples) e dois tipos de grãos (duro e dentado). Os testadores SynD e SynF são populações de milho de polinização aberta com grãos dentados e duros, respectivamente, e FSH e DSH são híbridos simples com grãos duros e dentados, respectivamente. O testador SynD possibilitou a maior expressão de variância genética entre os cruzamentos com as linhagens. A capacidade geral de combinação (CGC) das linhagens e a capacidade específica de combinação (CEC) entre linhagens e testadores foram significativas, enquanto que os efeitos de CGC dos testadores foram não significativos. Concluiu-se que os testadores SynD e SynF mostram-se adequados para identificar linhagens com maiores efeitos de GCA e é possível identificar novas linhagens com alto potencial heterótico com cada um dos quatro testadores utilizados.

Os objetivos deste trabalho foram determinar o controle genético da eficiência no uso do nitrogênio (EUN), identificar a importância das eficiências na absorção (EAN) e na utilização (EUtN) na sua composição, e quantificar relação entre produção de matéria seca da parte aérea (MPS) e do sistema radicular com a EUN e com seus componentes. Foram avaliadas 41 combinações híbridas em duas disponibilidades de N: baixa (BN) e alta (AN). Utilizou-se o delineamento de blocos ao acaso com duas repetições, em arranjo fatorial simples (combinação híbrida x disponibilidade de N). As análises estatísticas foram realizadas por meio das equações de modelos mistos. Correlações de elevada magnitude foram detectadas entre EAN e EUN, bem como entre essas eficiências e a MPS, tanto em BN como em AN. Em ambas as disponibilidades de N, efeitos genéticos aditivos apresentaram maior importância para os caracteres associados à EUN. Dessa forma, a seleção baseada no desempenho individual de linhagens quanto à MPS pode possibilitar a obtenção de genótipos com alta EUN. Independentemente da disponibilidade de N, a EAN é o componente mais importante da EUN.

Visando a amostragem de acessos para comporem uma coleção núcleo de milho, foram amostrados acessos introduzidos e melhorados da Coleção Ativa de Germoplasma da Embrapa Milho e Sorgo, localizada em Sete Lagoas, MG. A estratégia de amostragem utilizada foi baseada em análise multivariada, sendo adotada intensidade de amostragem de 20%. A estratificação dos acesos introduzidos foi realizada principalmente de acordo com o país de origem, local de avaliação e tipo de grão. Para os acessos melhorados considerou-se principalmente o tipo de grão e a instituição responsável pela realização do melhoramento do acesso. Verificou-se a necessidade de se realizar a caracterização e avaliação de muitos acessos introduzidos e melhorados. Foi possível observar a existência de variabilidade genética entre os acessos introduzidos e melhorados. As características altura de planta e peso de mil grãos foram as que mais contribuíram para a discriminação dos genótipos. A utilização combinada do método de Tocher tendo como medida de dissimilaridade a distância euclidiana invertida e a análise de dispersão gráfica com base nos três primeiros componentes principais foi eficiente. Foi possível a amostragem de acessos para comporem uma coleção núcleo de milho com base em análise multivariada a partir de dados de caracterização e avaliação.Aiming at the selection of accessions to compose a core collection of maize, were sampled access introduced and improved of Active Germplasm Bank at Embrapa Milho e Sorgo, located in Sete Lagoas, MG, Brazil. The sampling strategy was based in multivariate analysis, and adopted a sampling rate of 20% of accesses. Stratification of introduced accessions was in according with the country of origin, place of assessment and type of grain. For improved access was considered mainly the type of grain and the institution responsible for improvement of access. There is a need to perform the characterization and evaluation of many introduced and improved. It was possible to observe the existence of genetic variability among accessions. The plant height and thousand grain weight were the main contributors to the discrimination of genotypes. The combined use of the method of Tocher and as dissimilarity measure the Euclidian distance reversed and graphic dispersion analysis based on the first three principal components was effective. It was possible the selection of accessions to compose a core collection of maize based on multivariate analysis from the characterization and evaluation data.

O objetivo do trabalho foi avaliar o estabelecimento populacional das comunidades das plantas daninhas, durante seis anos agrícolas consecutivos de milho cultivado no sistema plantio direto orgânico e tradicional, intermediado por um sistema de plantio convencional. Os experimentos foram conduzidos nos anos agrícolas 2003/04 até 2008/09. O delineamento experimental adotado foi o de blocos casualizados com quatro repetições. Os tratamentos avaliados foram: SDT1 (semeadura direta sem adubação e com aplicação de herbicidas no manejo das plantas daninhas); SDT2 (semeadura direta com adubação mineral na dose de 300 kg ha-1 do formulado 8-28-16 + 100 kg ha-1 de nitrogênio em cobertura, e com aplicação de herbicidas); SDT3 (semeadura direta, adubação com composto orgânico, na dose de 40 m³ ha-1, e com aplicação de herbicidas); e SDO (semeadura direta utilizando composto orgânico, na dose de 40 m³ ha-1, e roçada no manejo das plantas daninhas). Concluiu-se que a dinâmica populacional de plantas daninhas na cultura do milho foi influenciada pelo manejo do solo (aração e gradagem) e que o tipo de adubação não proporcionou alteração na dinâmica populacional.The aim of this work was to evaluate the weed establishing (and unwanted plant) populations during six consecutive agricultural years for maize crops. The systems studied were till, both organic and traditional, intermediated by a traditional plantation system. The experiments were carry out in the agricultural years 2003/04 until 2008/09, in the experimental area in southeast of the Minas Gerais State), which is owned by the Federal University of Viçosa. The treatments were SDT1 (till without fertilizer and herbicide application ); SDT2 (till with mineral fertilizer (300 kg ha-1 with of 8-28-16 (N-P-K) plus 100 kg ha-1 of nitrogen for side fertilization, and the herbicide application): SDT3 (till with fertilizer with organic compost in a dose of 40 m³ ha-1 and herbicide application ); SDO (organic till with organic compost in a dose of 40 m³ ha-1, and mowing). We can conclude that the herbicide application or the clearing of the ground stimulated a greater alteration in the establishing of weed (unwanted plant) communities than the type of fertilizer used.

The objectives were to identify maize germplasm for the organic productions system and to compare the genetic effects of the grain yield of maize cultivars in organic and conventional production systems. Diallel crosses were made between six maize cultivars and the hybrid combinations were evaluated in conventional and organic production systems. The hybrid combinations produced different grain yields in the two production systems. The interaction between general combining ability and production systems was significant for grain yield, ear height and number of ears. This indicates that the additive genetic effects differ in organic and conventional production systems. The specific combining abilities (SCA) were significant for grain yield and plant height, indicating a significant difference between the non-additive effects. However, the SCA x production systems interactions were not significant for those traits. It was concluded that for the development of maize cultivars for the organic production system, selection must be made in the specific environment for the expression of favorable alleles that confer advantages for adapting to this system; the general combining ability of genitors is different for the two production systems, but the specific combining ability isn't different in organic and conventional systems.Os objetivos foram identificar germoplasma de milho para o sistema de produção orgânica e comparar os efeitos genéticos da produtividade de grãos de cultivares de milho em sistemas de produção orgânico e convencional. Para isso, cruzamentos dialélicos foram realizados entre seis cultivares de milho e as combinações híbridas avaliadas em sistemas de produção orgânico e convencional. Os híbridos apresentaram diferentes produtividades de grãos nos dois sistemas de produção. A interação entre a capacidade geral de combinação (CGC) e os sistemas de produção (SP) foi significativa para produtividade de grãos, altura de espiga e número de espigas. Isso indica que os efeitos genéticos aditivos diferem nos sistemas de produção orgânica e convencional. A capacidade de combinação específica (CEC) foi significativa para produtividade de grãos e altura de plantas o que indica a diferença significativa entre os efeitos não aditivos dos genitores. Entretanto, a interação CEC x SP foi não significativa para esses caracteres. Conclui-se que, para o desenvolvimento de cultivares de milho para sistema de produção orgânico, a seleção deve ser feita no ambiente específico para a expressão dos alelos favoráveis que conferem vantagens para adaptar a este sistema; a capacidade geral de combinação dos genitores é diferente nos dois sistemas de produção, mas a capacidade específica de combinação é semelhante nos sistemas orgânico e convencional.

O objetivo desse trabalho foi caracterizar uma população de milho por meio da análise de parâmetros genéticos em baixa e alta disponibilidade de nitrogênio. Assim, foi realizado experimento em delineamento em blocos ao acaso, com 162 linhagens, em dois ambientes contrastantes quanto à disponibilidade de nitrogênio, em esquema fatorial com três repetições. A população apresentou variabilidade genética para produtividade de grãos em baixo nitrogênio, com redução na média de altura de espiga, teor de clorofila, número de espigas, peso de espiga e produtividade de grãos em relação ao ambientes sem estresse. Os coeficientes de correlação genética entre produtividade de grãos e as outras características variaram de acordo com as doses de nitrogênio aplicadas. O número de espigas apresentou alta correlação genética com produtividade de grãos sob estresse, além de maior herdabilidade comparada à obtida em alto nitrogênio, possibilitando assim seu uso na seleção indireta de linhagens produtivas de milho cultivadas sob estresse de nitrogênio.The aim of this study was to characterize a maize population through the genetic parameters in high and low nitrogen availability. Thus, the experiment was conducted in a randomized block design with 162 lines in two contrasting environments in nitrogen availability in a factorial design with three replications. The population showed genetic variability for grain yield in low nitrogen, reducing the ear height, chlorophyll content, the number of ears, ear weight and grain yield in relation to the environment without stress. The coefficient's genetic correlation between grain yield and other characteristics vary according to levels of nitrogen applied. The number of ears showed high genetic correlation with grain yield under stress and high heritability compared with obtained under a high nitrogen, thus enabling its use for indirect selection of yield lines of maize grown under nitrogen stress.

Tem sido observada, em milho, a redução da absorção de nitrogênio (N), por causa da deficiência de fósforo (P), mas o efeito dessa combinação na seleção de genitores ainda precisa de estudos. Os objetivos deste trabalho foram avaliar os efeitos das inter-relações de P e N na capacidade de combinação e seleção de genitores de milho. As 28 combinações híbridas (CH), obtidas de um dialelo completo entre oito genótipos de milho e três testemunhas, foram avaliadas em quatro ambientes, obtidos pelas combinações de alta e baixa disponibilidade de P e N. Avaliaram-se o rendimento de grãos (RG) e as características secundárias: altura de plantas (AP) e espigas (AE), índice de colheita (IC), peso volumétrico (PV), prolificidade (PRL) e massa seca da parte aérea (MSPA). O efeito do estresse de N no RG foi similar em baixo e alto P. O genótipo P3041 apresentou alto RG em todos os ambientes. As correlações genéticas das características secundárias com o RG foram afetadas pelos ambientes. Em alto P, a capacidade geral de combinação (CGC) foi significativa para RG apenas em alto N. Em baixo P, a CGC apresentou significância em ambos os níveis de N. Os genótipos AG1051 e P3041 tiveram estimativas positivas de CGC em todos os ambientes. Conclui-se que, para o rendimento de grãos, a CGC somente não é importante em alto P e baixo N e a CEC não é importante em estresse de P ou N.

Com o desenvolvimento de cultivares modernos, a produtividade do milho tem aumentado e, consequentemente, a demanda por N segue a mesma tendência. Objetivou-se com este trabalho avaliar o efeito da época de aplicação de N sobre a produtividade de grãos e sua distribuição nos componentes da planta de milho, na presença e ausência de adubação de molibdênio, em sistema plantio direto. O experimento foi conduzido no ano agrícola de 2006/07, na Estação Experimental de Coimbra-MG. O delineamento experimental foi o de blocos casualizados, com três repetições, no esquema fatorial 3 x 2 + 1, sendo três épocas de aplicação de N, na ausência e na presença de adubação com molibdênio (Mo), e uma testemunha sem fertilização. Os tratamentos consistiram de: T1- aplicação total de N 15 dias antes do plantio, sem molibdênio; T2 - aplicação total de N no plantio, sem molibdênio; T3 - aplicação total de N na época em que o milho se encontrava com quatro folhas completamente desenvolvidas, sem molibdênio; T4 - aplicação total de N 15 dias antes do plantio, com molibdênio; T5 - aplicação total de N no plantio, com molibdênio; T6 - aplicação total de N na época em que o milho se encontrava com quatro folhas completamente desenvolvidas, com molibdênio; e T7 - testemunha sem N, sem aplicação de Mo. O cultivar utilizado foi o híbrido simples AG 9010. O melhor suprimento de N ao longo do ciclo e a maior produtividade foram obtidos com a aplicação do fertilizante no estádio de quatro folhas expandidas do milho. Não foi encontrado efeito da adubação molíbdica sobre as características avaliadas. A aplicação do N na pré-semeadura do milho, 15 dias antes do plantio, demonstrou não ser recomendável para as condições de solo e clima estudadas. A parte da planta do milho de maior alocação de 15N foi o grão. A recuperação média de 15N na planta proveniente do fertilizante foi de 6 %.Maize yield has increased with the development of modern cultivars and the demand for N has followed the same trend. The objective of this study was to evaluate the effect the timing of N application on grain yield and distribution in maize plant components in the presence and absence of Mo fertilizer under no-tillage. The experiment was conducted in the 2006/07 growing season, at the Experimental Station of Coimbra-MG. The experiment was arranged in a randomized block with three replications in a factorial 3 x 2 + 1 design, with three N application dates, in the absence on presence of Mo fertilization, and an unfertilized control. The treatments consisted of: T1-total N applied 15 days before planting, without Mo, T2-total application of N at planting without Mo; T3-total N application at the stage of four completely developed leaves, without Mo; T4-total N application 15 days before planting, with Mo, T5-total application of N at planting, with Mo; T6-total N application at the stage of four completely developed leaves, with Mo, and T7-control without N application without Mo, applied to the corne single hybrid AG 9010. Nitrogen supply throughout the cycle was best and yields were highest with fertilizer application at the four expanded leaves stage. No effect of Mo fertilizer was observed on the characteristics evaluated. Application of N prior to corne sowing (15 days before planting) is not recommended for the climate and soil conditions studied. Most applied N was allocated in the grain. The average 15N recovery from fertilizer in plants was 6 %.

Neste trabalho, objetivou-se avaliar o potencial genético da população de milho UFV 7 para o melhoramento em Minas Gerais. Foram instalados três experimentos com a população de milho UFV 7, em três regiões de Minas Gerais, na safra 2006/2007. Houve interação genótipos x ambientes para todos os caracteres. Foi verificada variabilidade genética para produtividade de grãos, altura de plantas e altura de espigas na população de milho UFV 7, nas três regiões. Na região Sudeste, a população de milho UFV 7 apresentou as maiores estimativas de parâmetros genéticos. A população UFV 7 apresentou alta produtividade de grãos, 9 112kg ha-1, no Sudeste, média produtividade, 6 510kg ha-1, no Oeste, e baixa, 4 572kg ha-1, na região Central. As estimativas de herdabilidade e CVg/CVe, para produtividade, foram superiores a 60% e 1,00, respectivamente. A produtividade de grãos teve correlação genética significativa e positiva com a altura de planta e altura de espiga, na região Oeste e na Central, e com a prolificidade na região Central e região Sudeste. Conclui-se que a população de milho UFV 7 apresenta potencial para extração de linhagens na região Central; potencial para uso imediato na região Sudeste e para novos ciclos de seleção na região Oeste de Minas Gerais, e a seleção para PG aumenta indiretamente a altura de planta e altura de espiga, nas regiões Oeste e Central.The objective was to assess the genetic potential of maize population UFV 7 for breeding in Minas Gerais, Brazil. Three experiments were installed with the maize population UFV 7 in the three regions of Minas Gerais, in the harvest of 2006/2007. There was genotype x environment interaction for all characters. It was observed genetic variability for grain yield, plant height and ear height in maize population UFV 7, in the three regions. The Southeast region was where the maize population UFV 7 had the highest parameters. The population UFV 7 presented high grain yield, 9 112kg ha-1 in the Southeast, average grain yield, 6 510kg ha-1 in the West and low, 4 572kg ha-1 in the Central Region. Heritability estimate and CVg / CVe for grain yield were higher than 60% and 1.00, respectively. Grain yield had significant and positive genetic correlation with plant height and ear height, in Western and Central, and the prolificacy in Central and Southeast. For maize population UFV 7 it was conclude that it has potential for extraction of lines in the Central Region; it has the potential for immediate use in the Southeast and for new cycles selection in the Western Region of Minas Gerais. The selection for PG provides an indirect increase in plant height and ear height, in the West and Central.

The objective of this study was to evaluate the use of SREG GGE biplot methodology and factor analysis to stratify the genotype×environment interaction in maize. Forty-nine early maize hybrids were evaluated in nine environments. The experimental design used was a 7×7 square lattice with two replicates. Each plot consisted of two 5m long rows spaced 0.90m apart. Grain yield data were used to perform the analysis. The results indicated the existence of two mega-environments in the State of Minas Gerais, Brazil, for early maize hybrids. The stratification of the environment by factor analysis was more selective to join the similarity the according with cultivar performance. However, this approach did not identify specific genotype x environment interactions, which is possible through SREG GGE biplot analysis.O objetivo deste estudo foi avaliar a metodologia SREG GGE biplot e a análise de fatores na estratificação da interação genótipos×ambientes em milho. Foram avaliados 49 híbridos comerciais de milho de ciclo precoce em nove ambientes. Foi utilizado o delineamento látice quadrado 7×7, com duas repetições. Cada parcela consistiu de duas linhas de 5m espaçadas por 0,90m. Para a realização das análises, foram utilizados dados de produtividade de grãos. Os resultados indicaram a existência de dois mega-ambientes no Estado de Minas Gerais para híbridos de milho de ciclo precoce. A estratificação de ambientes pela análise de fatores mostrou-se mais seletiva em reunir ambientes pela similaridade de desempenho dos cultivares, mas não evidenciou as interações genótipos x ambientes específicas, o que foi possível pela análise SREG GGE biplot.

O objetivo deste trabalho foi identificar os efeitos genéticos que controlam a herança de caracteres associados à eficiência de utilização do fósforo (EUP) em milho e determinar as relações entre esses caracteres. Foi realizado um dialelo entre seis cultivares de milho do qual foram obtidas 15 combinações híbridas. Estas cultivares foram avaliadas em alta e baixa disponibilidade de fósforo, em casa de vegetação e campo. Foram medidas a resposta das plantas à disponibilidade de fósforo (RU) e as características associadas às eficiências de utilização e translocação do nutriente. As combinações híbridas apresentaram interação significativa com a disponibilidade de P, para os caracteres massa de matéria seca da planta (MSP), teor de P na planta (PAP) e razão entre as massas de matéria seca da parte aérea e da raiz (RMS). A interação entre capacidade geral de combinação e RU foi significativa para PAP e RMS e, entre capacidade específica de combinação e RU, para MSP e PAP. As EUP em baixa e alta disponibilidade do nutriente estiveram correlacionadas entre si e com RU. A EUP em baixa disponibilidade de P não se correlacionou com a produtividade de grãos. Contudo, sob alta disponibilidade do nutriente, esses parâmetros se correlacionaram. Os efeitos não aditivos têm maior importância para caracteres relacionados à EUP, de modo que a seleção deve ser realizada nas combinações híbridas.The objective of this work was to determine the genetic effects that control the inheritance of characters associated with the phosphorus utilization efficiency (PUE) in maize, and to determine the relationship among them. A diallel between six maize cultivars was performed and 15 hybrid combinations were obtained from it. These cultivars were evaluated in high and low phosphorus availability in the greenhouse and field. Plant response to nutrient availability (RU) and traits associated to utilization and translocation efficiency were measured. There were significant interactions between hybrid combinations and phosphorus availability for plant dry matter mass (MSP), P concentration in plants (PAP), and the ratio between shoot and root dry matter masses (RMS). The interaction between general combining ability and P availability was significant for RMS and PAP, and the one between specific combining ability and P availability, for MSP and PAP. The PUE in low and high P were correlated with each other and with RU. The PUE at low P availability was not correlated to grain yield. However, in high soil P availability these parameters were correlated. Non additive effects are more important for traits related to PUE, so that selection should be carried out on hybrid combinations.

Low availability of phosphorus in the soil is one of the principal limiting factors in plant development and plant production. Plants have developed adaptive mechanisms for these environments that vary among species and genotypes within a species. The capacity of plants to explore the soil, transform unusable P forms to usable forms, develop relationships with mycorrhiza fungi, among other traits, influence the plant efficiency in these environments. The objective of this study was to evaluate morphological root characteristics related to mechanisms of phosphorus acquisition in sorghum lines of the sorghum improvement program at Embrapa. Nine lines were used to study the root system in a soil with two levels of phosphorus (5 and 20 mg dm-3). For this characterization a WinRhizo v. 4.0 image analyzer was used. Genetic variability was observed at low phosphorus levels for total root length, very fine root length, fine root length, total root surface area, root surface area of very fine root, root surface area of fine root and number of root branches, suggesting that different mechanisms of phosphorus acquisition may be occurring in environments with low and high phosphorus availability. Root length and root surface area appear to be more important for plant adaptation to low phosphorus levels than root volume and root diameter. Specific root length and root tissue density were the most useful parameters related to plant productivity at low phosphorus. These characteristics could be useful parameters for selection in sorghum improvement programs.

O presente trabalho teve como objetivo selecionar os genótipos maiseficientes na absorção e utilização de fósforo em solos de cerrado na safrinha. O ensaio foi constituído de 47 tratamentos (genótipos) e foi conduzido na área experimental da Universidade Federal do Tocantins, Campus de Gurupi. Para simular ambientes com baixo e alto nível de fósforo, foram utilizadas doses de 25 e 113 kg ha-1 de P2O5 na semeadura, respectivamente. Para identificar os cultivares adequados aos ambientes, utilizou-se metodologia que sugerem a classificação das cultivares quanto à eficiência no uso e resposta a aplicação do fósforo (eficiência e resposta). Concluiu-se que osgenótipos eficientes na absorção e utilização de fósforo e responsivos ao incremento de P foram UFVM77-0331, UFVM77-0307, UFVM77-0333, UFVM77-0381, UFVM77-0313, UFVM77-0305, UFVM77-0377 e UFVM77-0345. This work aimed to select the most efficient genotypes in phosphorus absorption and utilization in cerrado soils during corn second crop. The essay was constituted of 47 treatments (genotypes) and conducted at the experimental area of the Universidade Federal do Tocantins, Gurupi Campus. In order to simulate environments with high and low levels of phosphorus, doses of 25 and 113 kg ha-1 of P2O5 were applied in the seeding, respectively. In order to identify the cultivars adequate to the environments, the study applied the methodology that suggest cultivar classification should be conducted according to use efficiency and response to phosphorus application (efficiency and response). It was concluded that the genotypesefficient in phosphorus absorption and utilization and responsive to P increase were UFVM77-0331, UFVM77-0307, UFVM77-0333, UFVM77-0381, UFVM77-0313, UFVM77-0305, UFVM77-0377 and UFVM77-0345.

The objectives of this work were to caracterize the tropical maize germplasm and to compare the combining abilities of maize grain yield under different levels of environmental stress. A diallel was performed among tropical maize cultivars with wide adaptability, whose hybrid combinations were evaluated in two sowing dates, in two years. The significance of the environmental effect emphasized the environmental contrasts. Based on grain yield, the environments were classified as favorable (8,331 kg ha-1), low stress (6,637 kg ha-1), high stress (5,495 kg ha-1), and intense stress (2,443 kg ha-1). None of the genetic effects were significant in favorable and intense stress environments, indicating that there was low germplasm variability under these conditions. In low and high stresses, the specific combining ability effects (SCA) were significant, showing that the nonadditive genetic effects were the most important, and that it is possible to select parent pairs with breeding potential. SCA and grain yield showed significant correlations only between the closer environment pairs like favorable/low stress and high/intense stress. The genetic control of grain yield differed under contrasting stress environments for which maize cultivars with wide adaptability are not adequate.O objetivo deste trabalho foi caracterizar o germoplasma de milho e comparar a capacidade de combinação da produtividade do milho em ambientes com diferentes graus de estresse. Um dialelo foi realizado entre cultivares de milho tropical com ampla adaptabilidade, cujas combinações híbridas foram avaliadas em duas épocas de plantio, em dois anos. A significância do efeito ambiental mostrou que os ambientes foram contrastantes. Com base na produtividade, os ambientes foram classificados como: favorável (8.331 kg ha-1); com baixo estresse (6.637 kg ha-1); com alto estresse (5.495 kg ha-1); e com intenso estresse (2.443 kg ha-1). Nenhum dos efeitos genéticos foi significativo nos ambientes classificados como favorável e com intenso estresse, o que indica haver baixa variabilidade para as combinações genéticas nesses ambientes. Em baixo e alto estresse, os efeitos da capacidade de combinação específica foram significativos, o que mostra que os efeitos genéticos não aditivos foram os mais importantes, e que é possível selecionar pares de genitores com potencial para melhoramento. A capacidade geral de combinação e a produtividade de grãos apresentaram correlações significativas somente entre os ambientes mais próximos como favorável/baixo estresse e alto/intenso estresse. O controle genético da produtividade de grãos difere em ambientes contrastantes quanto ao estresse para os quais as cultivares de milho com ampla adaptabilidade não são adequadas.

O objetivo deste trabalho foi caracterizar a diversidade genética de acessos de tomateiro do Banco de Germoplasma de Hortaliças da Universidade Federal de Viçosa (BGH-UFV) e avaliar a importância relativa de caracteres na determinação dessa diversidade. Setenta acessos de tomateiro foram avaliados em três experimentos em blocos ao acaso, com três repetições, com as cultivares Santa Clara e Débora Plus como testemunhas. No primeiro experimento, de janeiro a julho de 2002, foram avaliados 30 acessos; no segundo, de agosto a dezembro de 2002, e no terceiro, de janeiro a julho de 2003, 20 acessos. No estudo de diversidade genética, foram realizadas análises de variância agrupada, agrupamento das médias pelo teste de Scott-Knott e agrupamento dos acessos pelo método de Tocher. Foi realizado, também, o estudo da importância relativa de caracteres pelo método de Singh e por variáveis canônicas. A variabilidade para 16 características foi verificada pelo teste de Scott-Knott, e os acessos foram separados em dez grupos pelo agrupamento de Tocher. Existe grande diversidade genética entre acessos de tomateiro do BGH-UFV, com ampla variação tanto para características morfológicas quanto para características agronômicas e de qualidade.The objectives of this work were to characterize the genetic diversity of tomato accessions from the Vegetable Germplasm Bank of Universidade Federal de Viçosa (BGH-UFV) and to evaluate the relative importance of characters in determining this diversity. Seventy tomato accessions were evaluated in three experiments in a randomized block design with three replicates, using the Santa Clara and Débora Plus cultivars as controls. In the first experiment (January to July 2002), 30 accessions were evaluated; in the second (August to December 2002) and the third (January to July 2003) experiments, 20 accessions were evaluated. The divergence study was performed through the joint analysis of variance, the grouping of the averages by the Scott-Knott test, and the grouping of accessions by Tocher's method. The study of the relative importance of characters was done by the Singh method and by canonical variables. The variability for 16 characters was verified by the Scott-Knott test, and the accessions were separated in ten groups according to Tocher's method. There is great genetic diversity between tomato accessions of BGH-UFV, with high variation in morphologic, agronomic and quality characteristics.

The objective of this research was to obtain and select maize base populations, efficient in phosphorus absorption and utilization, in a savannah soil, in the municipality of Gurupi, Tocantins State, Brazil (11°43’S, 49°15’W, altitude 300 m). The study assessed 45 hybrid combinations (populations), derived from crosses among ten commercial hybrids, in a dystrophic red-yellow Latossol (Oxisol), under low (25 kg ha-1 of P2O5) and high (113 kg ha-1 of P2O5) phosphorus doses. The traits evaluated were grain yield, plant height, ear height, and number of days for female flowering. The data were submitted to variance analyses and the means of genetic treatments were grouped by the Scott-Knott test. The populations with outstanding behavior in both environments and, therefore, most adapted to the target region, are derived from the following crosses: CO 32 x DKB 350, Z 8480 x CO 32, Z 8480 x P30F88, C 901 x CO 32, C 901 x P30F88, Z 8480 x DKB 350, CO 32 x Z 8420, C 901 x Z 8420, C 901 x C 333 B, Z 8420 x DKB 350, C 901 x Z 8480, DKB 350 x Z 8410, P30F88 x Z 8420, AG 9010 x DKB 350, and P 3041 x AG 9010. It was also concluded that the populations show plant height and ear height appropriate for growing in the region, and that the environment with the lowest dose of phosphorus delays the flowering of the populations. KEY-WORDS: Zea mays; P low input; P mineral stress; Cerrado soil. Este trabalho teve como objetivo a obtenção e a seleção de populações base de milho eficientes na absorção e utilização de fósforo em solo de Cerrado, no município de Gurupi, Estado do Tocantins. O estudo avaliou 45 combinações híbridas (populações), derivadas do cruzamento de dez híbridos comerciais, em Latossolo Vermelho-Amarelo Distrófico, sob baixa (25 kg ha-1 de P2O5) e alta (113 kg ha-1 de P2O5) dose de fósforo. Os caracteres avaliados foram produtividade de grãos, altura da planta, altura da espiga e número de dias para o florescimento feminino. Os dados foram submetidos a análises de variância e as médias dos tratamentos genéticos foram agrupadas pelo teste Scott-Knott. As populações que mostraram comportamento destacado, nos dois ambientes, consideradas mais adaptadas à região alvo deste estudo, derivam dos seguintes cruzamentos: CO 32 x DKB 350, Z 8480 x CO 32, Z 8480 x P30F88, C 901 x CO 32, C 901 x P30F88, Z 8480 x DKB 350, CO 32 x Z 8420, C 901 x Z 8420, C 901 x C 333 B, Z 8420 x DKB 350, C 901 x Z 8480, DKB 350 x Z 8410, P30F88 x Z 8420, AG 9010 x DKB 350 e P 3041 x AG 9010. Concluiu-se, também, que as populações apresentam altura de planta e de espiga adequadas para o cultivo na região e que o ambiente com menor nível de fósforo retarda o florescimento das populações. PALAVRAS-CHAVE: Zea mays; baixo insumo; estresse mineral; solo de Cerrado.

The objective of this study was to discriminate maize inbred lines byevaluating root characteristics obtained by digital images analysis when different nitrogen (N) rates were applied. Six maize inbred lines from Embrapa Maize and Sorghum were grown in five liter pots containing Red Latosol – medium textured, and two different N rates (zero and 2 mmol. L-1) were used. Nitrogen was applied as ammonium nitrate. A randomized complete blocks design was used, with three replications. Root and shoot features were evaluated on plants harvested 23 days after sowing. Significant interactions were observed between strains and N rates for root length, root surface area, very fine root length, surface area of very fine roots, surface area of thick roots, very fine root volume, shoot dry matter and total dry matter. The inbred line CMS 28-7.1 showed a lower very fine root volume/total root volume ratio compared to the other inbred lines. At low N availability, root characteristics allowed to distinguish maize inbred lines and very fine roots volume.

The objectives of this research were to evaluate the genetic variability and predict genetic gain in the white maize landrace rescued in Barbacena, Minas Gerais, Brazil. The Brazilian maize landraces have economic and social importance for certain areas in Brazil, and research on this germplasm is very important for local food security. Three experiments were carried out with 100 half-sib progenies, in Campos dos Goytacazes, RJ, Coimbra and Barbacena, Minas Gerais, Brazil. These sites were chosen for their soil and climatic differences. An analysis of variance was significant among the progeny for all characters, indicating the presence of genetic variability between the three populations. In Campos dos Goytacazes and Coimbra, the genetic variation of the white maize landrace was responsible for most of the phenotypic variance in grain yield and can be used in selection cycles. There was no significant genetic variance in grain yield in Barbacena. For the white maize landrace it was concluded that: the characters of the component of productivity such as plant density and number of plants with kernels can produce indirect genetic gain for grain yield and are suitable for breeding; prebreeding of the maize landrace is necessary before being used directly in the elite germplasm; the population contains high genetic variability and opportunities for genetic gain; the average agronomic traits are suitable only for traditional production systems with few inputs, and polyculture; the difference between environments produces specific responses in the progeny i.e. there is a progeny x environment interaction.Os objetivos deste trabalho foram avaliar a variabilidade genética e predizer os ganhos genéticos de uma população crioula de milho branco resgatada em Barbacena, Minas Gerais (MG), devido à importância social e econômica do milho branco em determinadas localidades brasileiras, à manutenção e ao resgate de populações crioulas e aos poucos trabalhos sobre esse tipo de grão. Para tanto foram instalados três experimentos, com 100 progênies de meios-irmãos, em Campos dos Goytacazes, Rio de Janeiro (RJ), Coimbra e Barbacena (MG), escolhidos pelas diferenças edafoclimáticas. Pela análise de variância foram verificadas diferenças significativas entre as progênies para todos os caracteres, o que indicou a presença de variabilidade genética na população para os três locais. Em Campos dos Goytacazes e Coimbra, a variância genética da população crioula de milho branco foi responsável pela maioria da variância fenotípica para produtividade de grãos, podendo ser explorada em ciclos de seleção. Em Barbacena, não foi detectada variância genética significativa para a produtividade de grãos. Para a população crioula de milho branco Barbacena, conclui-se que caracteres do componente primário de produtividade como estande final e número de plantas com grãos podem apresentar ganhos genéticos direto e indireto com a produtividade e são adequados para o melhoramento. No entanto, é necessário o pré-melhoramento da população antes desta ser utilizada diretamente em germoplasma elite. Além disso, foi observado que a população apresenta variabilidade genética e ganhos genéticos preditos altos; as médias das características agronômicas são adequadas somente para o sistema produtivo tradicional com poucos insumos e policultivo; e a diferença entre os ambientes proporciona resposta específica das progênies, ou seja, interação progênie x ambiente.

The aim of this study was to compare the multivariate methods GGE (Genotype main effects and Genotype xEnvironment interaction) and AMMI (Additive Main effects and Multiplicative Interaction) with the method of Eberhart andRussell for interpreting genotype x environment interaction. The AMMI and GGE analysis explained around 50% of the sumof squares of the genotype x environment interaction, whereas the method of Eberhart and Russell explained only 9.1 and15.8% each year. The cultivars classified as minor contribution to the genotype x environment interaction by methods ofAMMI and GGE were also the same classification method of Eberhart and Russell. The AMMI and the GGE biplot analysesare more efficient than the Eberhart and Russell. The GGE biplot explains a higher proportion of the sum of squares of theGxE interaction and is more informative with regards to environments and cultivar performance than the AMMI analysis.

The objectives of this work were to evaluate the genotype x environment (GxE) interaction for popcorn and to compare two multivariate analyses methods. Nine popcorn cultivars were sown on four dates one month apart during each of the agricultural years 1998/1999 and 1999/2000. The experiments were carried out using randomized block designs, with four replicates. The cv. Zélia contributed the least to the GxE interaction. The cv. Viçosa performed similarly to cv. Rosa-claro. Optimization of GxE was obtained for cv. CMS 42 for a favorable mega-environment, and for cv. CMS 43 for an unfavorable environment. Multivariate analysis supported the results from the method of Eberhart & Russell. The graphic analysis of the Additive Main effects and Multiplicative Interaction (AMMI) model was simple, allowing conclusions to be made about stability, genotypic performance, genetic divergence between cultivars, and the environments that optimize cultivar performance. The graphic analysis of the Genotype main effects and Genotype x Environment interaction (GGE) method added to AMMI information on environmental stratification, defining mega-environments and the cultivars that optimized performance in those mega-environments. Both methods are adequate to explain the genotype x environment interactions.Os objetivos deste trabalho foram avaliar a interação genótipo x ambiente (GxA) em milho-pipoca e comparar dois métodos de análise multivariada (AMMI e GGE). Os tratamentos foram nove cultivares de milho-pipoca, plantadas em quatro épocas de semeadura em cada ano de cultivo em 1998/1999 e 1999/2000. O delineamento foi em blocos ao acaso, com quatro repetições. A cultivar Zélia foi a que menos contribuiu para a interação GxA. As cultivares Viçosa e Rosa-claro mostraram desempenhos similares. A otimização da interação GxA foi obtida com a cv. CMS 42 para mega-ambientes favoráveis e com a cv. CMS 43 para ambientes desfavoráveis. Os resultados das análises multivariadas corroboraram os resultados do método de Eberhart & Russell. A análise gráfica do método Additive Main effects and Multiplicative Interaction (AMMI) é simples e permite tirar conclusões sobre estabilidade, desempenho genotípico, divergência genética das cultivares, e sobre os ambientes que otimizam o desempenho das cultivares. A análise gráfica do método Genotype main effects and Genotype x Environment interaction (GGE) acrescentou informações de estratificação ambiental ao AMMI e definiu mega-ambientes e as cultivares que tiveram suas performances otimizadas nesses ambientes. Ambos os métodos são adequados para explicar a interação genótipo x ambiente.

The objectives of this work were to study the genetic control of grain yield (GY) and nitrogen (N) use efficiency (NUE, grain yield/N applied) and its primary components, N uptake efficiency (NUpE, N uptake/N applied) and N utilization efficiency (NUtE, grain yield/N uptake), in maize grown in environments with high and low N availability. Experiments with 31 maize genotypes (28 hybrid crosses and three controls) were carried out in soils with high and low N rates, in the southeast of the state of Minas Gerais, Brazil. There was a reduction of 23.2% in average GY for maize grown in soil with low N, in comparison to that obtained with high N. There were 26.5, 199 and 400% increases in NUtE, NUpE, and NUE, respectively, for maize grown with low N. The general combining ability (GCA) and specific combining ability (SCA) were significant for GY, NUE and NUpE for maize grown in high N soil. Only GCA was significant for NUpE for maize grown in low N soil. The GCA and SCA for NUtE were not significant in either environment. Additive and non-additive genetic effects are responsible for the genetic control of NUE and GY for maize grown in soils with high N availability, although additive effects are more important.O objetivo deste trabalho foi estudar o controle genético da produtividade de grãos (PG) e da eficiência no uso de nitrogênio (EUN, produção de grãos/N aplicado) e seus componentes primários - eficiência de absorção (EAbN, N absorvido/N aplicado) e utilização (EUtN, produção de grãos/N absorvido) -, em milho cultivado em ambientes com alta e baixa disponibilidade de nitrogênio. Trinta e um genótipos de milho (28 cruzamentos entre híbridos comerciais e três testemunhas) foram avaliados em solos com alta e baixa doses de aplicação de N. Houve redução de 23,2% na média de PG em milho cultivado em solo com baixo teor de N, em relação à obtida com alto N. Com baixo teor de N no solo, observaram-se aumentos de 26,5, 199 e 400% em EUtN, EAbN, e EUN, respectivamente. Em milho cultivado em solo com alto teor de N, as capacidades geral (CGC) e específica (CEC) de combinação foram significativas em PG, EUN e EAbN. Em milho de solos com baixo teor de N, apenas a CGC, na EAbN, foi significativa. A CGC e a CEC não foram significativas, em nenhum dos ambientes, na EUtN. Efeitos genéticos aditivos e não aditivos são responsáveis pelo controle genético da EUN e PG, em milho cultivado em solos com elevada disponibilidade de N, mas os efeitos aditivos são mais importantes.

The objectives of this study were to select maize genitors and determine the selection strategy for obtaining high quality silage maize hybrids. An experiment was conducted involving 45 hybrids obtained using a diallel scheme among commercial hybrids and four controls, in a triple lattice 7 x 7 design. The general combining ability (GCA) and specific combining ability (SCA) were significant for dry matter yield (DMY) and crude protein (CP), indicating additive and non-additive gene effects in genetic control. Only GCA was significant for plant height (PH), green matter yield (GMY) and hemicelluloses (HEM), which indicates a greater importance of additive than non-additive genetic effects in genetic control. The GCA and SCA of neutral detergent fiber (NDF) and acid detergent fiber (ADF) did not differ significantly between the hybrids, but there was a variance of 33% to 49% for NDF and 15 to 24% for ADF. The cultivars P30F90 and SHS4070 were the most recommended for increasing PH, GMY and DMY, while 2B619 and DKB466 were recommended to increase CP, and BRS3003 and AG1051 to reduce HEM. The hybrid combinations XB8028 x DKB 466, Valent x CD307, Valent x DKB466, SHS4070 x AG1051, BRS3003 x 2B619 and 2B619 x AG1051 are promising for maize silage production, because of their associated productive and qualitative traits.

Postharvest handling of corn is an important factor in the production of green corn, since it can represent up to 50% of the total production cost of this crop. As a few studies have analyzed the procedures for this fresh product, the objective of this work was to evaluate the effect of storage conditions and type of package on starch contents in green corn grains. Two corn hybrids were used in this experiment: AG 1051 and DINA 170, harvested at approximately 80 percent moisture. Two assays were conducted, being one under refrigeration at 5ºC ± 0.8ºC, and another at room temperature (22ºC ± 1.8ºC). In these conditions, three different types of package were evaluated: ears with husks, ears without husks and ears wrapped in a PVC film (without husks). Evaluations and samplings were done every three days for the treatments at room temperature and every five days for the treatments at 5ºC. Starch quantification was done using anthrone reaction. A completely randomized design with a subdivided plots scheme was used, with two replications. The means were compared by Turkey test at 5% probability. Results showed that, at room temperature, grains from wrapped ears presented lowest starch contents, regardless hybrid analyzed, and PVC film was unable to reduce the starch accumulation rates, at the tested temperatures, in both hybrids, during the ten days of storage.

This study was carried out to estimate the genetic parameters for grain weight of two maize populations, for verifying their genetic potential under contrasting conditions concerning water availability. Forty nine half-sib families (HSF) were randomly taken from each of the two populations, UFVM 100 and UFVM 200, in order to evaluate the tolerance to water deficit, using two sets of experiments representing water deficit and optimum irrigation conditions. The experiments were set up under a 7 x 7 lattice design, with two replications. Sprinkler irrigation was applied and a tensiometer used for its management. The experiments were irrigated whenever the soil water potential showed -0.03 MPa. However, the experiments under water stress were not irrigated during seven days, until the soil water potential reaches -0.09 to -0.1 Mpa, at vegetative, flowering and grain filling stages. The experimental plot comprised a row length 5m, 0.90m row spacing and plants spaced 0.20m within rows. Grain yield was determined for each plot. Analysis of variance was performed, involving the 49 HSF of each population, in each production system, and corresponding estimates of the genetic parameters were obtained. Within each production systems, genetic progress was estimated for each population assuming selection of the 15% superior HSF and subsequent recombination. Results showed that the experiments did not reveal sufficient genetic variation, in both populations, able to be explored in selection programs under water deficit conditions and also a low concordance level between the performance of the families under normal irrigation and water deficit.

O objetivo deste trabalho foi avaliar a influência dos componentes do rendimento e caracteres da planta, na produção de grãos, em trigo sob desfolha, por meio da decomposição das correlações por meio de análise de trilha. O experimento foi conduzido em Viçosa, MG, em 2004. Os tratamentos constituíram-se de três níveis de desfolha e uma testemunha, com três variedades de trigo - Anahuac, BRS 207 e BR 24 -, com quatro repetições. A desfolha foi realizada com a retirada do limbo da folha bandeira, das segunda e terceira folhas superiores. Avaliaram-se: rendimento de grãos, peso do hectolitro, massa de mil grãos, número de espigas por parcela, número de grãos por espiga, biomassa seca do colmo, biomassa seca da palha da espiga, biomassa seca total, rendimento de grãos por espiga, biomassa seca do colmo individual, biomassa seca da palha da espiga individual e biomassa seca total por planta individual. A redução da biomassa seca do colmo levou a menores perdas de rendimento de grãos, pela remobilização de fotoassimilados com a desfolha. A massa de mil grãos e o número de grãos por espiga foram os principais componentes de rendimento. A seleção direta para esses caracteres é estratégia eficiente para aumentar o rendimento de grãos em trigo sob desfolha.The objective of this work was to evaluate the influence of yield components and plant characters in grain production, in wheat under defoliation, through correlations decomposition using path analysis. The experiment was accomplished in Viçosa, MG, Brazil, in 2004. The treatments consisted of three levels of defoliation and a control, with three wheat varieties - Anahuac, BRS 207 and BR 24 -, with four replicates. Defoliation was carried out by removing the blade of flag leaves from the second and third top leaves. The following parameters were evaluated: grain yield, hectolitric weight, one thousand-grain weight, number of spikes per plot, number of grain per spike, culm dry biomass, spike-straw dry biomass, total dry biomass, grain yield per spike, total dry biomass of individual culm, straw dry biomass of individual spike and total dry biomass per individual plant. The reduction in culm dry biomass led to lower losses of grain yield because of the higher remobilization of photoassimilates with defoliation. Thousand-grain weight and number of grain per spike were the main yield components. The direct selection for these characters is an efficient strategy to increase grain yield in wheat under defoliation.

The objectives of this work were to determine the genetic correlation and define the strategies for obtain maize cultivars for traditional production system. For that, the white maize landrace population was rescued in Barbacena, MG and two experiments were installed with 100 half sib progenies using lattice triple in Barbacena and Campos dos Goytacazes, RJ. The estimates of correlations were different for each local requiring different strategy for trait selection due to contrast edaphoclimatic condition. The additive genetic correlationswere significant among primary production components and the productivity. On the other hand, the additive genetic correlations among primary and secondary production components were non significant. The traits related with flowering showed genetic correlation with productivity and primary production components, but not for secondary production components. Concluded that the increasing of productivity can be reached with direct or indirect selection for all environments; the indirect selection for number of plants/ area and number of plants with ears with kernels can be viability strategy in experiments in the small producers or by themselves instead of to select directly the productivity; the selection for increasing productivity without change the plant architecture is possible and adequate for traditional production system.

This study was conducted to evaluate the yield of two maize varieties cropped with organic and mineral fertilizations either associated or unassociated. The randomized experimental design was used under a factorial scheme 2 x 3 x 2, with four replicates. The first factor corresponds to two maize varieties (Nitrodent and Nitroflint), whereas the second one represents three levels of mineral fertilization: without mineral fertilizer; 300 kg/ha of 4-14-8 + 100 kg/ha ammonium sulfate (S.A.); and 600 kg/ha of 4-14-8 + 200 kg/ha S.A. The third factor represents two organic fertilization levels: without organic fertilizer; and 40 m3/ha organic compound. The experimental plot consisted of eight plant rows with 8m length each one and 1m spacing from each others, so totaling 64 m2 area. The yield of the maize grains by plot were evaluated, and the data were subjected to variance analysis (test ¿ 5%). The averages were compared by Tukey test at 5% probability level. Both varieties Nitrodent and Nitroflint only cropped under the organic system reached more than 6.500 kg/ha. The exclusive organic cropping system provided higher yields of maize grains, compared to the conventional system. No significant differences were found between the exclusive organic system and the combination of both organic and conventional systems upon the grain yield of the Nitrodent variety.

The objective of this study was to estimate the genetic potential of two maize populations, in order to verify their genetic potential under two production systems (with and without nitrogen stress). So, 49 half-sib families (FMI) of the population UFVM 100 and 49 FMI of the population UFVM 200 were randomly taken. The 7 x 7 lattice design was used, with two replicates. The high nitrogen level was established with planting fertilization more two side-dressing fertilizations, so totaling 120 kg/ha N (40 kg/ha N in planting fertilization; 40 kg/ha N at the 15 days after emergency - DAE; 40 kg/ha N at 30 DAE). The low nitrogen level was only 20 kg/ha N in planting fertilization. The experimental plot consisted of one row with 5m length and 0.90m spacing between rows and 0.20m among plants inside the rows. All experiments were subjected to water deficit (irrigation interruption) at flowering stage, during 7-day period, until soil water potential was between -0.09 to -0.1 MPa. The grain yield was evaluated in each plot. The variance analysis relative to those 49 FMI of each population in each production system was accomplished according to recommendation by Cochran and Cox (1957), whereas the estimates of the genetic parameters were performed according to method 1 presented by Silva et al. (1999), when considering the lattice experiments. After the individual analyses, those 15% more productive FMI were selected in each production system to estimate the expected selection gain when recombining them. It was found that only the population UFVM 100 shows genetic variability to be explored by selection based on half-sib families, for grain production under low N availability conditions; the estimates of the genetic parameters associated to grain yield were similar as for high and low nitrogen; the consistence of the agreement level between the families´ performances under low and high availability of nitrogen was low, therefore pointing out the need for conducting a specific improvement program when the objective is to obtain material adapted to nitrogen stress conditions.

O objetivo deste trabalho foi estudar o efeito do espaçamento e do modo de aplicação da adubação nitrogenada na cultura do milho. A pesquisa foi desenvolvida no ano agrícola 2003/04, na Estação Experimental de Coimbra – UFV, em um experimento disposto no delineamento de blocos casualizados, com 4 repetições, no esquema fatorial 3 x 3 x 2 (3 cultivares – UFVM 100, AG 9010 e AG 1051, 3 modos de aplicação do nitrogênio – 0, 120 kg ha-1 de N no plantio e 30 kg ha-1 de N no plantio + 90 kg ha-1 de N, na quarta folha completamente expandida, e 2 espaçamentos entre fileiras – 1,0 e 0,5 m). A aplicação de nitrogênio, parcelado ou todo no plantio, elevou a altura de plantas das cultivares, independentemente do espaçamento; o espaçamento de 0,50 m, proporcionou aumento de 8% na produtividade de grãos; não houve diferença significativa na produtividade de grãosdas cultivares estudadas com a aplicação de 120 kg ha-1 de N no plantio ou parcelado (30 kg ha-1 de N no plantio + 90 kg ha-1 de N, na quarta folha completamente expandida).The aim of this work was to evaluate the effect of nitrogen application mode and spacing on corn culture. The study was carried out in 2003/04 agricultural years, at the Experimental Stationof Coimbra – UFV. The experiment was installed in a complete randomised block design. Treatments were arranged in a 3 x 3 x 2 factorial scheme with four replicates (three cultivates - UFVM 100, AG 9010 and AG 1051; three nitrogen application modes - 0, 120kg ha-1 of N in planting and 30 kg ha-1 at sowing + 90 kg ha-1 at four fully expanded leaves; and two plant spacing – 1.0 and 0.5 m). Either at sowing or parcel out, the nitrogen application increased the plant height in all plant spacing used; the spacing reduction, from 1.0 m to 0.50 m, provided an increase of 8% in grains productivity; the 120 kg ha-1 nitrogen application, either at sowing or divided in two modes (30 kg ha-1 at sowing and 90 kg ha-1 atfour fully expanded leaves), did not show any effect on the characteristics evaluated.

The objective of this research was to identify sources of maize germplasm (hybrid and open pollination bred populations, ancient and local) efficient in absorption and utilization of itrogen for seed production at Zona da Mata of Minas Gerais State, Brazil. The trials were carried out at Viçosa, Minas Gerais State (altitude 650 m, 20º45'20" S), during 2001/2002 growing season. To simulate environments with average and severe nitrogen stress, 20 kg ha-1 and 120 kg ha-1 doses on top dressing, espectively, were used. The data traits evaluated were submitted to analysis of variance and cultivar means were grouped by Scott-Knott test. The interactions of germoplasm types with nitrogen doses were not significant (p > 0.05). The highest seed yield and ear weight cultivars were the bred populations UFVM3, AL25, and BR106, the hybrids AG122 and BR 201, and the local populations B3, B11, B12, B6, B9, and B22. The environment with the largest nitrogen level presented the highest seed yield, ear weight, plant and ear height, and number of ears by plant. KEY-WORDS: Zea mays; breeding; N stress. O objetivo deste trabalho foi identificar fontes de germoplasma de milho (híbridos e populações de polinização aberta melhoradas, antigas e locais) eficientes na absorção e utilização de nitrogênio para a região da Zona da Mata de Minas Gerais. Os experimentos foram conduzidos em Viçosa, MG (650 m de altitude, 20º 45'20" latitude sul) no ano agrícola 2001/2002. Para simular ambientes com médio e intenso estresse de nitrogênio, foram utilizadas, em cobertura, as doses de 20 kg ha-1 e 120 kg ha-1 de N, respectivamente. Os dados dos caracteres avaliados foram submetidas à análise de variância e as médias das cultivares foram agrupadas pelo teste de Scott-Knott. As interações dos tipos de germoplasma com as doses de nitrogênio foram não significativas (p > 0,05). As cultivares que apresentaram maior produtividade de grãos e peso de espigas foram as populações melhoradas UFVM3, AL25 e BR106, os híbridos AG122 e BR201, e as populações locais B3, B11, B12, B6, B9 e B22. O ambiente em se que empregou maior nível de nitrogênio proporcionou maiores produtividades de grãos, peso de espiga, alturas de planta e de espiga, e maior número de espigas por planta. PALAVRAS-CHAVE: Zea mays; melhoramento; estresse mineral.

Avaliou-se a influência de doses elevadas de molibdênio aplicadas via foliar sobre componentes de produção e rendimento de grãos dos feijoeiros Novo Jalo e Meia Noite. Conduziu-se o experimento entre março e junho de 2002 em Coimbra, Estado de Minas Gerais, utilizando delineamento em blocos casualizados, com quatro repetições,arranjados no esquema fatorial 7 x 2, (sete doses de Mo combinadas com os cultivares Novo Jalo e Meia Noite). As doses 80 e 160 g ha-1 foram aplicadas 20 dias após a emergência (DAE) das plântulas em dose única. As doses (320 e 640 g ha-1) foram ministradas em trêsaplicações (15, 20 e 25 DAE), e as doses (1.280 e 2.560 g ha-1) em quatro aplicações (15, 20, 25 e 30 DAE). Os componentes de produção, exceto o número de sementes por vagem e o rendimento de grãos foram influenciados pela adubação molíbdica. A dose ótima estimada de Mo para o feijoeiro, em ambos os cultivares, foi de 255 g ha-1. Doses de molibdênio até 2.560 g ha-1 não promoveram decréscimos em nenhum dos componentes da produção nem no rendimento de grãos.The influence of high doses of molybdenum through foliar application was evaluated on production components and grain yield of the bean plants Novo Jalo and Meia Noite. The experiment was carried out fromMarch to June, 2002, on Coimbra, Minas Gerais State. A randomized block design, with four repetitions, arranged in the factorial outline 7 x 2 (seven doses of molybdenum combined with Novo Jalo and Meia Noite cultivars) was used. The doses 80 and 160 g ha-1 were applied 20 days after the plantules emergence (DAE) in only dose. The doses (320 and 640 g ha-1) were applied in three applications (15, 20 and 25 DAE), and the doses (1,280 and 2,560 g ha-1) in four applications (15, 20, 25 and 30 DAE). The production components,except the number of seeds for green bean and the income of grains, were influenced by the molybdenum fertilization. The expected optimum rate of molybdenum for the bean plant, in both cultivars, was of 255 g ha-1. Molybdenum doses up to 2,560 g ha-1 did not decrease any of the components of the production nor the grain yield.

In family agriculture in the Brazilian Northeast, it is a common practice to plant corn seeds harvested during previous cultivations. Because weed control in those properties does not get appropriate attention, it is possible that weeds interfere with seed quality. The objective of this work was to evaluate the effects of weed control on germination, vigor (plantlet, first count and dry matter data), dimensions, and weight of corn seeds. Two experiments were carried out as a random block design with split-plots, and five replicates, either with six (AG 405 C, DKB 425, EX 6005, AG 2060, BA 8517, and BA 9513) or four (BA 9012, BA 8512, EX 4001, and EX 6004) cultivars, respectively. In both, cultivars were assigned to plots and weed control to subplots. In the first experiment, weed control was achieved by means of two hoeings. In the second, control was accomplished by two hoeings or by intercropping with cowpea (Vigna unguiculata (L.) Walp.). In both experiments, it was verified that weeds did not have an influence on germination percentage or on first count data (except for one cultivar); however, plantlet dry matter weight was higher in hand hoed plots. In those plots, width, height, and seed weight were also higher. In both experiments, the cultivars were not different in relation to germination percentage. In the first experiment, the cultivars were different with respect to first count data, while in the second experiment they were different with regard to first count and plantlet dry matter data.

An intense metabolic activity is observed in plant organs harvested at immature stage, especially in corn, which may increase the postharvest losses. The use of storage techniques and adequate hybrids can reduce such losses, allowing longer period for commercialization. The present work had the goal to evaluate the influence of different forms of storage on weigh loss of corn harvested at milk stage for “in natura” consumption of hybrids DINA 170 and AG 1051. The experiment was disposed in complete random design with four replicates, arranged in factorial array of 3 X 2 X 2 (three storage conditions: ear included in husks, ear exposed and ear wrapped in PVC film), (two hybrids: DINA 170 and AG 1051), (two temperatures of storage: room temperature and 5 oC). Fresh weight loss was determined daily and the averages were compared by Tukey test at 5% probability. Ears wrapped in PVC had lower weight loss, regardless of the temperature of storage and hybrid used. At room temperature, the ears included in husks of hybrid DINA 170 showed lower weight loss. The ear exposed treatment the hybrid AG 1051 showed lower weight loss. No significant differences were observed at storage at 5 oC, regardless of the treatment.

The objective of this study was to evaluate the yield and combining ability of maize cultivars (AG4051, AL30,AL25, D270, D170, and AG1051) in contrasting environments. The trials were conducted in the growing season 2002/2003,in Viçosa, Capinópolis and Florestal, state of Minas Gerais. The effects of hybrids were significant by the F test, as well astreatments x environments, hybrid combinations x environments, and controls x environments. This indicates the possibilityof increasing the yield in these regions by capitalizing on the genotype x environment interaction, by selecting and recombiningcultivars for each site. Among the cultivars and their hybrid combinations, AG1051 and AG4051 x AL30, respectively,performed best in the mean of the three locations. The most indicated combinations for each site were: AG4051 X AL30 andAL30 X D270 in Viçosa, AG4051 X AL25 and AL30 X D170 in Florestal and, D170 x AG4051 and AL25 x D270 inCapinópolis.

Imazapyr has been used in Brazilian eucalypt cultivation for the maintenance of clearings and coppicing control in areas undergoing stand reform. However, inquiries have been made as to the final fate of the molecule. Imazapyr root exudation in eucalypt plants was evaluated through a bioassay under greenhouse conditions, by applying different herbicide doses (0.000, 0.375, 0.750, 1.125, and 1.500 kg ha-1 a.i.) on Eucalyptus grandis seedlings derived from vegetative propagation, hydroponically cultivated in 2.500 ml vases. Forty-day-old seedlings of the same clone were used as bioindicators, transplanted to the vases two days after herbicide application. After a period of 13 days of coexistence, the sprayed plants were removed and discarded; ten days later, the visual symptoms of toxicity were evaluated and the total dry biomass (aerial part and roots) of the bioindicators were determined. The lowest herbicide dose (0.375 kg ha-1 a.i.) affected the total biomass and growth, being most evident in the aerial part, with larger I50 for root dry biomass. The E. grandis seedlings exuded imazapyr, and/or its metabolites, in concentrations capable of affecting the growth of plants of the same species.Na eucaliptocultura brasileira, vem-se utilizando o imazapyr para manutenção de aceiros e erradicação de cepas e brotações em áreas de reforma dos povoamentos. Entretanto, têm sido levantadas indagações quanto ao destino final da molécula. A exsudação radicular de imazapyr em plantas de eucalipto foi avaliada por meio de bioensaios em casa de vegetação, aplicando-se diferentes doses do herbicida (0,000; 0,375; 0,750; 1,125; e 1,500 kg ha-1 i.a.) sobre mudas de Eucalyptus grandis, provenientes de propagação vegetativa e cultivadas em sistema hidropônico, em vasos de 2.500 mL. Como bioindicador, empregaram-se mudas do mesmo clone com 40 dias de idade, as quais foram transplantadas para os vasos dois dias após a aplicação do herbicida. Depois de um período de 13 dias de convivência, retiraram-se as plantas que receberam a aplicação, descartando-as; 10 dias após, foram avaliados os sintomas visuais de toxicidade e determinadas as biomassas secas de parte aérea e raízes das mudas do bioindicador. A menor dose do herbicida (0,375 kg ha-1 i.a.) afetou o crescimento e a produção de biomassa total, sendo mais pronunciado na parte aérea, com maior valor de I50 na biomassa seca de raiz. As mudas de E. grandis exsudam o imazapyr e, ou, seus metabólitos, em concentrações capazes de afetar o crescimento de plantas da mesma espécie.

The objective of this work was to evaluate the accuracy of the chlorophyll meter readings (SPAD index) for early assessing nitrogen content on maize leaves and to proportionate subsidies for recommending nitrogen fertilization. The assay was carried out with three simple maize hybrids (DKA333B, P32R21 and AG9010) and six forms of nitrogen application during crop cycle, totaling 120 kg ha-1: 100% at sowing stage (S); 40% at S and 60% at 4th leaf stage; 40% at S and 60% at 8th leaf stage; 20% at S and 80% at 4th leaf stage; 20% at S and 80% at 8th leaf stage and 20% at S, 40% at 4th leaf stage and 40% at 8th leaf stage. The experiment was arranged in randomized blocks with four replications in split-plot design, being maize hybrids the plot and portioning of nitrogen fertilization the split. Determinations of the leaf chlorophyll content (SPAD index), evaluated with the chlorophyll meter, leaf nitrogen content, and grain yield were done. The chlorophyll meter readings were efficient to provide early diagnose of nitrogen content at the fourth tally expanded leaf of maize cultivars AG9010 (super-early cycle) and P32R21 (early cycle). Concerning the hybrid DKB333B (normal cycle) there was no correlation between chlorophyll meter reading (SPAD index) and nitrogen content on the fourth fully expanded leaf.