A nonlinear model applied to genotype x environment interaction analysis in maize

Na hipótese de que os efeitos de ambientes sobre os genótipos, na manifestação fenotípica de um caráter, se dá de forma multiplicativa, foi estudado um modelo não-linear, que é multiplicativo apenas em seus parâmetros genético e ambiental. Dados de produtividade de espigas de milho (Zea mays L.) foram utilizados para verificar a possível adequação do modelo não-linear. Verificou-se que: (1): ambientes favoráveis, em que a média do caráter é maior, propiciam melhor discriminação entre os genótipos ou cultivares; (2): nas análises conjuntas usuais, a soma de quadrados de uma interação fica dependente da dos efeitos principais envolvidos; (3): o ajuste de médias de tratamentos de diferentes ensaios, onde apenas algumas testemunhas são comuns a todos eles, deve ser feito por fatores multiplicativos, e não, aditivos; (4): o coeficiente de regressão linear, comumente empregado na análise da estabilidade de cultivares, passa a ser positivamente correlacionado com a média geral das cultivares. As análises de 64 ensaios de milho indicaram que: (1) o modelo multiplicativo teve eficiência igual ou superior ao modelo linear; (2): o efeito multiplicativo dos ambientes sobre os genótipos foi responsável, em média, por 11,1% da interação de genótipos com ambientes, variando de 10.2% a 16,8%.Under the assumption that environmental effects act multiplicatively on genotype effects, a nonlinear model was studied, which is multiplicative for the main effects but additive for deviations. Experimental corn (Zea mays L) yield data of cultivars were analysed, in order to determine the applicability of the nonlinear model. The following consequences could be demonstrated: (1): in better environments in which higher mean values of the trait are observed, discrimination among genotypes or cultivars is favored; (2): in the usual joint analysis the interaction sum of squares depends on these due to the main effects; (3): the adjustment of treatment means of different experiments designed such that only some checks are common over the group of experiments, should be made through multiplicative factors rather than additive ones; (4): the linear regression coefficients, commonly used for the stability analysis of cultivars, becomes positively correlated with the means of the cultivars, over environments, to the analysis of corn yield data of 64 experiments, it could be verified that: (1) the nonlinear model showed equal or higher efficiency than the linear one; (2): the multiplicative action of environment on genotypic effects explained on the average, 11,1% of the cultivars x locations interaction, varying from 102% to 16.2%

Caracterização física de frutos de pequizeiro (caryocar brasiliense).

The objectives of the present study were to characterize pequi fruits from Cerrado and to indicate some strategies of investigation, conservation and utilization of their genetic variability. Fruits were collected during two consecutive crop seasons (2007/2008 and 2008/2009) in eight Cerrado regions. Their physical characteristics were evaluated, and data were submitted to descriptive analysis, analysis of variance and simple correlations between characteristics. The results showed high phenotypic variability for most fruit characters in all sampled regions. Considering that some of this variability is heritable, there is a potential genetic gain by selection. The correlation analysis showed significant positive correlations among important traits for pequi breeding. A large difference among regions was observed about their potential to supply attractive fruits to the consumer market

Caracterização física de frutos de pequizeiro (Caryocar brasiliense Camb.) do cerrado

The objectives of the present study were to characterize pequi fruits from Cerrado and to indicate some strategies of investigation, conservation and utilization of their genetic variability. Fruits were collected during two consecutive crop seasons (2007/2008 and 2008/2009) in eight Cerrado regions. Their physical characteristics were evaluated, and data were submitted to descriptive analysis, analysis of variance and simple correlations between characteristics. The results showed high phenotypic variability for most fruit characters in all sampled regions. Considering that some of this variability is heritable, there is a potential genetic gain by selection. The correlation analysis showed significant positive correlations among important traits for pequi breeding. A large difference among regions was observed about their potential to supply attractive fruits to the consumer market

Genética e progresso esperado na seleção de caracteres de crescimento em população de cagaiteira

The objective of this study was to estimate genetic parameters of quantitative traits in a living germplasm collection of Eugenia dysenterica. The genetic material consisted of 110 progenies derived from 10 natural Eugenia dysenterica subpopulations sampled in the southeastern region of the state of Goiás. The experiment was established in a complete randomized block design, with 110 treatments, four replications and one tree per plot. The study variables were total height, stem diameter and respective growth rates. After the analysis of variance some genetic parameters were estimated. The levels of genetic variation in the collection were high and the highest proportion was found within subpopulations. Highest coefficients of heritability and genetic variation were observed in subpopulations from the counties Catalão, Três Ranchos, Cristalina and Senador Canedo. Considering the promising expected progress for growth traits, this collection can be converted into an unrogued seedling seed orchard, aiming the production of improved seed.O objetivo deste trabalho foi estimar parâmetros genéticos de caracteres quantitativos da coleção de germoplasma in vivo de Eugenia dysenterica. O material de estudo foi composto por 110 progênies de dez subpopulações naturais de cagaiteira amostradas na Região Sudeste do Estado de Goiás. O delineamento experimental adotado foi de blocos completos casualizados, com 110 tratamentos, quatro repetições e uma árvore por parcela. As variáveis avaliadas foram altura total, diâmetro do fuste e respectivas taxas de crescimento. Após a análise de variância foram estimados parâmetros genéticos populacionais. As subpopulações naturais de cagaiteira tiveram altos níveis de variação genética e a maior proporção foi verificada dentro de subpopulações. Os maiores coeficientes de herdabilidade e de variação genética ocorreram nas subpopulações dos municípios de Catalão, Três Ranchos, Cristalina e Senador Canedo. Considerando os bons progressos esperados para caracteres de crescimento, essa coleção pode ser convertida em um pomar de sementes por mudas, sem desbaste, visando à produção de sementes melhoradas.CNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Heterosis in crosses among white grain maize populations with high quality protein

O objetivo deste trabalho foi investigar a heterose e seus componentes em 16 populações de milho de grãos brancos, de alta qualidade protéica. Estas populações foram divididas de acordo com o tipo de grão, para estabelecer grupos heteróticos diferentes. Os cruzamentos foram realizados entre populações dentadas e duras, seguindo o esquema dialélico parcial. Sete caracteres agronômicos foram avaliados em três locais, e quatro doenças foliares e a incidência de enfezamento, em um. O procedimento de quadrados mínimos foi aplicado à equação normal X'Xb = X'Y, para estimar os efeitos do modelo e suas respectivas somas de quadrados. Entre os componentes de heterose, na análise dialélica, detectou-se significância para heterose média em dias para o florescimento feminino e resistência a Puccinia polysora. As populações com performance superior no grupo dentado, independentemente da população dura usada no cruzamento, tendem a gerar híbridos intervarietais de produtividade superior. Na formação de compostos, são recomendadas as populações CMS 476, ZQP/B 103 e ZQP/B 101, do tipo dentado, e CMS 461, CMS 460, ZQP/B 104 e ZQP/B 102, do tipo duro, nesta ordem.The objective of this work was to investigate heterosis and its components in 16 white grain maize populations presenting high quality protein. These populations were divided according to grain type in order to establish different heterosis groups. The crosses were carried out according to a partial diallel cross design among flint and dent populations. Seven agronomic traits were evaluated in three environments while four leaf diseases and incidence of corn stunt were evaluated in one. Least square procedure was applied to the normal equation X'Xb = X'Y, to estimate the model effects and their respective sum of squares. Among the heterosis components, in diallel analysis, significance for average heterosis in grain yield, number of days to female flowering and to all evaluated diseases was detected. Specific heterosis was significant for days to female flowering and resistance to Puccinia polysora. Results concerned to grain yield trait indicate that populations with superior performance in dent group, no matter what flint population group is used in crosses, tend to generate superior intervarietal hybrids. In decreasing order of preference, the dent type populations CMS 476, ZQP/B 103 and ZQP/B 101 and the flint type CMS 461, CMS 460, ZQP/B 104 and ZQP/B 102 are recommended to form composites

Relation between the genetic variation of quantitative traits and the molecular markers in subpopulations (Eugenia dysenterica DC)

O objetivo do trabalho foi relacionar a diversidade genética medida a partir de três diferentes marcadores moleculares, com a variação genética quantitativa de caracteres poligênicos, estimada em ensaio de progênies, sob condições controladas. As progênies, oriundas de dez subpopulações naturais de cagaiteira do sudeste de Goiás, foram avaliadas em experimento em blocos completos casualizados, com quatro repetições e uma planta por parcela. Foram estimadas a herdabilidade ao nível de média de progênies (h mi ²) e o coeficiente de variação genética (CVgi) de cada subpopulação para a altura da planta e o diâmetro do fuste, por quatro anos, bem como para as respectivas taxas de crescimento. Estimativas da diversidade gênica (Hei) e do índice de fixação (f i) foram obtidas com dados de marcadores codominantes e dominantes. Correlação linear e regressão múltipla foram usadas para inferir sobre a associação entre a divergência quantitativa e molecular nos níveis intra e interpopulacional, A fraca correlação entre as medidas de divergência obtidas com marcadores moleculares dominantes e codominantes reduziu a expectativa de correlação positiva entre essas medidas e a diversidade quantitativa. Em geral, não foi confirmada a possibilidade de usar com segurança medidas de divergência molecular intrapopulacional para inferir a variação genética de caracteres quantitativos no nível de precisão que prevaleceu. Com o marcador baseado em maior número de locos (RAPD), verificou-se a possibilidade de uma inferência desse tipo. Em nível interpopulacional, encontrou-se associação mais pronunciada entre a divergência molecular e a quantitativa.This research aimed to measure the association between molecular diversity and the genetic variation of quantitative traits, estimated from a progeny trial, under controlled conditions. Ten natural subpopulations of cagaita tree from the southeast of Goiás State, Brazil, were investigated. The maternal families were evaluated in a trail using the randomized complete block design with four replications and a single tree per plot. Quantitative data were analyzed estimating the coefficient of heritability (h mi² ), on a progeny mean basis and the genetic coefficient of variation (CVgi) for each subpopulation. The traits considered were: plant height and the respective diameter and the corresponding annual rates of increment. Estimates of gene diversity (Hei) and fixation index (f i), available for the same subpopulations, based on isozymes, SSR and RAPD markers, were taken for comparison. Simple linear correlation and multiple regression analysis were used for measuring the association between those estimates on intra and interpopulation level. The weak correlation between gene diversity estimated with codominant and dominant markers reduced the expectation of a good correlation between those statistics and the genetic variation of the quantitative traits. In general, the possibility to infer the magnitude of quantitative variation within subpopulations, based on molecular gene diversity, was not confirmed. RAPD results were more promising, indicating the importance to have an adequate genomic coverage in this kind of research. On the other hand, the interpopulation level, a much better association was detected for all markers. The possibility of predicting quantitative variation based on molecular information was, therefore, not excluded.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP

Disentangling landscape effects on population genetic structure of a Neotropical savanna tree

ABSTRACTGeographical patterns of genetic variation and population structure and their relationship with habitat loss and fragmentation have been investigated at distinct scales and extents using spatially explicit statistics. Here, we analyzed population genetic structure of Dipteryx alata (Fabaceae; the “baru” tree), an economically important tree widely distributed in Central Brazil that is endemic to the “Cerrado” (savanna) biome, relating population genetic divergence with broad-scale landscape patterns. Genetic divergence among 25 populations, estimated based on eight microsatellite loci for a total of 644 individuals, was correlated with landscape features using several forms of Mantel tests (standard Mantel correlations, Mantel correlograms, partial correlations, and multiple regression). Patterns of genetic divergence are significantly correlated with human-driven landscape features of habitat loss and fragmentation, after taking into account isolation-by-distance and historical effects of range expansion after the last glacial maximum. Our findings present important implications for the conservation of this species, because interruption of gene flow by habitat loss and fragmentation jeopardize the persistence of population in the medium- and long term due to disruption of demographic patterns, increased endogamy, and recruitment problems.© 2014 Associação Brasileira de Ciência Ecológica e Conservação. Published by Elsevier Editora Ltd

Divergence among local populations of Eugenia dysenterica in response to edaphic patterns and spatial distribution

A domesticação e a utilização de espécies nativas em sistemas de produção muitas vezes são inviabilizadas pela falta de conhecimento prévio sobre a variabilidade genética. Uma vez quantificada, esta variabilidade pode ser útil tanto para o melhoramento genético da espécie quanto em programas de conservação. O objetivo deste trabalho foi avaliar a diferenciação, com base em caracteres genéticos e fenotípicos, entre dez subpopulações de Eugenia dysenterica DC. nativas da região sudeste do Estado de Goiás. Foram utilizados testes de Mantel a fim de comparar os padrões de variação genética, com base em oito locos isoenzimáticos, e caracteres fenotípicos (caracteres morfológicos e demográficos), entre as subpopulações, e estabelecer suas relações com as diferenças geográficas e edáficas entre as regiões. Os testes de Mantel sugeriram que o principal fator determinando a divergência genética é a distribuição geográfica das subpopulações, em um modelo no qual existe um balanço entre deriva genética atuando dentro das subpopulações e fluxo gênico em curtas distâncias ligando as subpopulações. A variação fenotípica, por sua vez, é melhor explicada pelos padrões edáficos e pela distribuição espacial. Esses resultados podem servir de guia para a coleta de germoplasma visando a sua utilização em programa de melhoramento genético desta espécie.The domestication and management of native plant species for uses in agricultural systems is usually constrained by the absence of knowledge about genetic variability, population structure and evolutionary processes involved in population differentiation in geographic space. A full understanding of these patterns and processes implies in analyzing multiple characters. In this paper, differentiation among ten local populations of Eugenia dysenterica DC. from Southeastern region of Goiás state, Central Brazil, was analyzed. Mantel tests were used to evaluate the relationships between genetic (eight loci from isozymes) and phenotypic (morphological and demographic characters) patterns of population differentiation, in relation to spatial distribution and edaphic differences among regions. The results from Mantel's tests suggested that the main factor acting on genetic differentiation is the geographic distribution of local populations, in a stochastic model that balances local drift within local population and short-distance gene flow among them. The phenotypic differentiation, on the other hand, is better explained by edaphic patterns and also by the geographic distribution. These results support the idea of neutral (or quasi-neutral) evolutionary processes in isozymic markers and shows that genetic divergence among local populations is highly structured in geographic space, independently of variations in edaphic patterns and phenotypic variation