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Search Results: 1 - 10 of 354252 matches for " Jefferson Luís Meirelles;Benin "
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Conseqüências da multicolinearidade sobre a análise de trilha em canola
Coimbra Jefferson Luís Meirelles,Benin Giovani,Vieira Eduardo Alano,Oliveira Ant?nio Costa de
Ciência Rural , 2005,
Abstract: A análise estatística do tipo multivariada vem crescendo consideravelmente, motivando a sua ampla utiliza o por parte dos pesquisadores criando, assim, grande demanda por conhecimentos específicos tanto a respeito da sua aplica o quanto das suas pressuposi es ou limita es. Para que a avalia o do grau de associa o entre diferentes caracteres de importancia agron mica tenha uma estimativa confiável em termos biológico, é de fundamental importancia identificar e quantificar o grau de multicolinearidade entre as variáveis estudadas. Além disso, os tipos de modelos estatísticos e matemáticos utilizados na determina o desta dependência linear entre as variáveis classificatórias ou independentes podem ou n o ser adequados a estimativas dos parametros biológicos avaliados. O presente trabalho tem como objetivo apresentar uma avalia o crítica sobre o grau de multicolinearidade identificado e avaliado sobre a análise de trilha analisada sobre partes de um experimento de canola. Os resultados permitem inferir que a aplica o da análise de trilha sobre o grau de multicolinearidade severa produz resultados sem nenhuma importancia biológica para o melhorista de plantas. No entanto, esta limita o pode ser facilmente identificada e corrigida através da análise de trilha com colinearidade empregando uma constante (k) na diagonal da matriz X?X. O modelo de análise com multicolinearidade severa, entretanto, superestimou, valores de coeficientes de correla o simples, comparativamente com a multicolinearidade fraca. Mesmo assim, pode n o ser necessariamente mais precisa, principalmente em virtude da avalia o de um número restrito de variáveis incluídas na análise ou de uma sobreposi o destas variáveis explicativas.
Conseqüências da multicolinearidade sobre a análise de trilha em canola
Coimbra, Jefferson Luís Meirelles;Benin, Giovani;Vieira, Eduardo Alano;Oliveira, Ant?nio Costa de;Carvalho, Fernando Irajá Félix;Guidolin, Altamir Frederico;Soares, Adriana Pires;
Ciência Rural , 2005, DOI: 10.1590/S0103-84782005000200015
Abstract: the statistical multivariate analysis has a widespread use by researchers, creating a large demand for specific knowledge regarding its application concerning its assumptions and or limitations. in order to evaluate the degree of association among different characters of agronomic importance with an estimative reliable in biological terms, it is striking to quantify the multicolinearity among the studied variables. in addition, the types of statistical and mathematical models used in determining this linear dependence between classifying or independent variables may or may not be adequate for estimatives of biological parameters evaluated. the present work has as objective to present a critical evaluation on the degree of multicolinearity identified and evaluated on the path analysis performed on parts of a canola experiment. the results allow to postulate that path analysis application on the degree of severe multicolinearity produces results with no biological importance for the plant breeder. however, this limitation can be easily identified and corrected through path analysis with colinearity employing a constant (k) on diagonal axis of x?x matrix. the model of analysis with severe multicolinearity, however overestimated the single correlation coefficient values comparatively with the weak multicolinearity. even so, it may not be necessarily more precise, mainly regarding the evaluation of a restricted number of variables included in the analysis or an overlapping of the explainable variables.
Tolerancia ao alumínio em cultivares de aveia branca sob cultivo hidrop?nico
Silva, José Antonio Gonzalez da;Carvalho, Fernando Irajá Félix de;Coimbra, Jefferson Luís Meirelles;Vieira, Eduardo Alano;Benin, Giovani;Oliveira, Ant?nio Costa de;Finatto, Taciane;Bertan, Ivandro;Silva, Giovani Olegário da;Correa, Maicon Rubira;
Bragantia , 2007, DOI: 10.1590/S0006-87052007000400008
Abstract: the use of hidroponic culture to evaluate tolerance to aluminum toxicity in oat genotypes can be performed by measuring root regrowth, allowing phenotypically to discriminate tolerant genetic constitutions sensitivity. twelve white oat cultivars indicated for cultivation in southern brazil were evaluated aiming at to characterize their aluminum tolerance, in order to use them as parents in crosses or to recommend them for in cultivation regions. aluminum concentration of 10, 15 and 20 mg l-1 were used in the hydroponic solution arranged in complete randomized blocks with three replications in 12 x 3 factorial designs. concentrations of 10, 15 and 20 mg l-1 were highly efficient for the identification of tolerant and sensitive oat genotypes. cultivars upf 16, urs 21, ufrgs 14, upf 19 and ufrgs 17 showed aluminum.
Resposta de híbridos de milho cultivados em diferentes épocas à popula??o de plantas e ao despendoamento
Sangoi, Luís;Guidolin, Altamir Frederico;Coimbra, Jefferson Luís Meirelles;Silva, Paulo Regis Fereira da;
Ciência Rural , 2006, DOI: 10.1590/S0103-84782006000500004
Abstract: current maize hybrids are more tolerant to the increasing of plant population than the hybrids used in the past. it is possible that modern hybrid's better adaptation to crowding is related to the lower apical dominance of the tassel over the ear. this experiment was aimed at evaluating the evolution on maize hybrids commercially released in different times the increase in plant population and at detecting if this progress is related to the reduction of apical dominance. the experiment was carried out in lages, sc, during the 1999/2000 and 2000/2001 growing seasons. a split-split plot design was used. three plant populations were tested in the main plots: 50,000, 75,000 and 100,000pl ha-1. four hybrids commercially released in the 60's, 70's, 80's and 90's, respectively, were assessed in the split plots. each hybrid was analyzed with preserved tassels and with tassel removed at booting in the split-split plot. the trials were installed in 10/30/1999 and 11/02/2000. grain yield was assessed using the variance and regression analyzes. the hybrid commercially released in the 90's (ag 9012) was more demanding in plant population to maximize grain yield when the conditions were favorable to yields higher than 10,000kg ha-1 (1999/2000). at this scenario, tassel interference on ear development was small. on the other hand, grain yield of all tested hybrids was increased by tassel removal under a lower yield plateau (2000/2001).there was no association between higher tolerance to crowding and greater response to detasseling, indicating that the tested hybrid higher endurance to dense stands was not related to the reduction in apical dominance of the tassel over the ear.
Análise de trilha dos componentes do rendimento de gr os em genótipos de canola
Coimbra Jefferson Luís Meirelles,Guidolin Altamir Frederico,Almeida Milton Luiz de,Sangoi Luís
Ciência Rural , 2004,
Abstract: O caráter rendimento de gr os é uma variável de associa o complexa, de importancia econ mica. Foi conduzido um ensaio no município de Lages-SC, no ano agrícola de 1996 no qual se utilizaram 12 genótipos de canola. O objetivo foi determinar a associa o e os efeitos diretos e indiretos de alguns caracteres sobre a produ o de gr os, através do estudo das correla es fenotípicas e pela análise de trilha. Utilizou-se o delineamento experimental em blocos casualizados, com quatro repeti es. De acordo com os resultados obtidos, pode ser concluído que n o há associa o entre os caracteres estatura de planta com os caracteres massa de mil gr os e rendimento de gr os. A análise de trilha revelou que os componentes primários popula o de plantas por unidade de área e número de gr os por planta tem o maior efeito direto sobre a variável rendimento de gr os. Por outro lado, o caráter número de gr os por planta é o maior responsável pelo aumento massa de mil gr os. O coeficiente de trilha evidenciou que o componente secundário número de gr os por síliqua tem o maior efeito direto sobre o rendimento de gr os.
Resposta de híbridos de milho cultivados em diferentes épocas à popula o de plantas e ao despendoamento
Sangoi Luís,Guidolin Altamir Frederico,Coimbra Jefferson Luís Meirelles,Silva Paulo Regis Fereira da
Ciência Rural , 2006,
Abstract: Os híbridos contemporaneos de milho s o mais tolerantes à eleva o da popula o de plantas do que os híbridos antigos. é possível que a melhor adapta o da cultura ao adensamento esteja relacionada com a menor dominancia apical do pend o sobre a espiga. Este trabalho foi conduzido objetivando avaliar a evolu o na tolerancia de híbridos de milho liberados comercialmente em diferentes épocas à eleva o na popula o de plantas, bem como observar se o progresso obtido esta associado à redu o na dominancia apical. O experimento foi conduzido no município de Lages, SC, durante os anos agrícolas de 1999/2000 e 2000/2001. Utilizou-se o delineamento experimental de parcelas sub-subdivididas. Na parcela principal, foram testadas três popula es de planta: 50.000, 75.000 e 100.000pl ha-1. Nas subparcelas, foram alocados quatro híbridos: Ag 12, Ag 28, Ag 303 e Ag 9012, liberados comercialmente para cultivo nas décadas de 60, 70, 80 e 90, respectivamente. Cada híbrido de milho foi analisado com pend es intactos e integralmente removidos durante o emborrachamento nas sub-subparcelas. Os ensaios foram implantados em 30/10/1999 e 2/11/2000. A por meio de análise de variancia e de regress o polinomial. O híbrido Ag 9012, liberado comercialmente para cultivo na década de 90, foi mais exigente em popula o de plantas do que os híbridos antigos para otimizar o seu potencial produtivo em 1999/2000, quando as condi es foram favoráveis à obten o de rendimentos de gr o superiores a 10.000kg ha-1. Neste ano agrícola, a interferência do pend o sobre o desenvolvimento das espigas foi pequena. Por outro lado, o rendimento de gr os de todos os híbridos respondeu positivamente ao despendoamento em 2000/2001, sob tetos produtivos mais baixos. N o houve associa o entre maior tolerancia ao adensamento e resposta ao despendoamento, indicando que a tolerancia a altas densidades populacionais n o esteve relacionada com a redu o da dominancia apical do pend o sobre as espigas.
Reflexos da intera??o genótipo X ambiente e suas implica??es nos ganhos de sele??o em genótipos de feij?o (Phaseolus vulgaris L.)
Coimbra, Jefferson Luís Meirelles;Guidolin, Altamir Frederico;Carvalho, Fernando Irajá Felix de;Coimbra, Silvana Manfredi Meirelles;Hemp, Silmar;
Ciência Rural , 1999, DOI: 10.1590/S0103-84781999000300009
Abstract: the importance of grains of legume plants for human feeding, specially black beans (phaseolus vulgaris l.), has stimulated the breeders to select genotypes with high grains yield potential and wide adaptability to different conditions of cultivation in southern brazil. the present work aimed at evaluating the reflexes of the genotype x environment interaction and its implications in the genetic gains of different selection approaches. the results revealed that the component of the interaction between genotype and environment overestimates the prediction of genetic parameters such as genetic variance and heritability. differences among these estimates were observed apparently due to a high percentage of the complex part of the interaction. besides, the genetic gains obtained with the direct selection were always superior to the indirect response. comparatively, the pair of environments 1x3 revealed correlated response inferior and of opposite sign to the other estimates for the other pairs of environments studied. the first environment was the one which accumulated the higher interaction genotype by environment. it can be concluded that the interaction component has great relevance in the estimates of genetic gains, evidencing that this influence should be considered in the selection and in the recommendation of specific genotypes of bean breeding programs.
Análise de trilha. I: análise do rendimento de gr?os e seus componentes
Coimbra, Jefferson Luís Meirelles;Guidolin, Altamir Frederico;Carvalho, Fernando Irajá Felix de;Coimbra, Silvana Manfredi Meirelles;Marchioro, Volmir Sergio;
Ciência Rural , 1999, DOI: 10.1590/S0103-84781999000200005
Abstract: thirty two bean accesses (phaseolus vulgaris l.) were evaluated for the influence of eight characters of agronomic importance the production of grains for unit of area, in lages/sc. the experiment, in randomized blocks with four repetitions, was conducted during the period off-season in the agricultural year of 1996/97. this work aimed estimating the degree of association between grain yield and its secondary components. the first group of variables (primary) was constituted by the number of grains per pod, number of pods per plant, weight of a thousand grains and the population of plants (pop). the second group (secondary), was constituted by the number of days between emergence and flowering (fl), number of days between emergence and harvesting point (mc), plant stature (ep) and the height of first pod insertion (pil). for the analysis of the trail coefficient, the direct and indirect effects of primary characters nlp and pmg were characterized and evaluated, revealing the large direct effects associated with the high correlation. the nlp was highly influenced by plants of shorter cycle and higher stature. the trail coefficients allow to point out that the largest direct effects on the yield of grains nlp are mainly associated to pmg, ngl and cycle of the plant.
Uso ou abuso em testes de compara??es de média: conhecimento científico ou empírico?
Bertoldo, Juliano Garcia;Coimbra, Jefferson Luís Meirelles;Guidolin, Altamir Frederico;Miqueloto, Aquidauana;Toaldo, Diego;
Ciência Rural , 2008, DOI: 10.1590/S0103-84782008000400039
Abstract: the objective of this research was to verify which are the main mistakes and the successes in the application of mean comparison tests in scientific studies, demonstrating viable alternatives in the sense of increasing the impartiality of the results obtained by researchers. one of the researcher's largest challenges is the interpretation of the obtained results in a trustworthy way. in spite of the concern of most researchers with the data analysis, many times certain disregard is observed in the interpretation of the results. thus, the incorrect application of statistical tests leads the researchers to publish information not completely reliable. one hundred and forty-eight papers dealing with one or more than one factor were evaluated. all of them are related to the crop production major area, published from 2002 to 2006, in the 'ciência rural', a brazilian scientific journal. most of the studies (72%) were classified as incorrect due to the abuse of means comparison tests. in addition, only 4% and 24% were classified respectively as partially correct and correct.
Correla??es can?nicas: II - análise do rendimento de gr?os de feij?o e seus componentes
Coimbra, Jefferson Luís Meirelles;Guidolin, Altamir Frederico;Carvalho, Fernando Irajá Felix de;Azevedo, Roni de;
Ciência Rural , 2000, DOI: 10.1590/S0103-84782000000100005
Abstract: thirty two bean genotypes (phaseolus vulgaris l.) were evaluated in lages/sc, brazil, on the influence of seven characters of agronomic importance on the production of grains per unit of area. the experiment, in randomized blocks with four repetitions, was driven in the off season period in the agricultural year of 1995/96. this work aimed to estimate the intensity the association between the primary and secondary components of grain yield. the first group of variables (primary) was constituted by the number of grains per pod, number of pods per plant and the weight of a thousand grains. the second group (secondary) consisted of number of days from emergency to flowering, number of days from emergency to harvesting point, plant stature and the first pod insertion point. for the analysis of canonical correlations, the importance of secondary agronomic characters was evident in the traits number of pods per plant and grains per pod and also the influence of both on the final grain yield. therefore, the coefficients of canonical correlations indicate that, in programs bean genetic improvement programs, to increase the production of grains one should select plants with larger number of pods per plant in order to obtain plants with higher stature and longer cycle.
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