Minimizing inter-genotypic competition effects to predict genetic values and selection in forestry genetic tests

The effect of competition is an important source of variation in breeding experiments. This study aimed to compare the selection of plants of open-pollinated families of Eucalyptus with and without the use of competition covariables. Genetic values were determined for each family and tree and for the traits height, diameter at breast height and timber volume in a randomized block design, resulting in the variance components, genetic parameters, selection gains, effective size and selection coincidence, with and without the use of covariables. Intergenotypic competition is an important factor of environmental variation. The use of competition covariables generally reduces the estimates of variance components and influences genetic gains in the studied traits. Intergenotypic competition biases the selection of open-pollinated eucalypt progenies, and can result in an erroneous choice of superior genotypes; the inclusion of covariables in the model reduces this influence

STABILITY AND PHENOTYPIC CHARACTERIZATION OF EXPERIMENTAL AND COMMERCIAL HYBRIDS MAIZE IN FOUR CROPPING SEASONS

The performance of maize is highly influenced by environmentalvariations, what can result in a low yield average, and instability varying from region toregion, month to month, and year cropping to year cropping. These environmentaleffects can be different for each cultivar, characterizing the genotype x environment interaction, which needs to be evaluated to a more efficient recommendation of cultivars.This work was developed in the experimental farm at Universidade Estadual Paulista(UNESP) – Campus de Ilha Solteira, in Selvíria, Mato Grosso do Sul, in order to evaluatethe stability and adaptability of 20 experimental three-way - hybrid crosses and thecommercial hybrids XB 8010, DKB 333B, TORK and P 3041. The experiments wereinstalled in November/2000, December/2000, January/2001 and March/2001 in acompletely randomized blocks design with four replications. The evaluated traits were:plant height, ear height, percentage of erect plants, grain yield and percentage of burnedgrains. The most responsive hybrids to the most favorable crop season were HS 10 x L2,HS 32 x L2, HS 83 x L3 and TORK for the percentage of erect plants and HS 7 x L1, HS32 x L1, HS 83 x L1, TORK and P 3041 for grain yield. Under these improvedenvironments, an increase on the percentage of burned grains incidence was detected forthe hybrids HS 83 x L1, HS 7 x L1, HS 83 x L3, HS 10 x L3 and P 3041, although thisincrease was within commercially acceptable levels

Neighborhood analysis in evaluation of sugarcane genotypes

O objetivo deste trabalho foi estudar diferentes covariáveis de competição em análises de vizinhança, e verificar sua eficiência no aumento da precisão experimental e as consequências no ordenamento de genótipos de cana-de-açúcar em termos de potencial produtivo. Foram utilizados dados da rede de ensaios do programa de melhoramento de cana-de-açúcar do Instituto Agronômico, instalados em 2002. O delineamento foi em blocos ao acaso, com três repetições. As parcelas constituíram-se de cinco sulcos de 8 m, espaçados 1,50 m entre si. A produtividade de colmos por hectare (TCH, Mg ha-1) foi avaliada no primeiro e terceiro cortes. As covariáveis "lateral", "ponta" e "quatro vizinhos" foram incluídas nos métodos de Papadakis, em duas variações do método médias móveis. Os métodos de Papadakis e médias móveis 1 não alteraram a precisão experimental em comparação à análise tradicional. O método médias móveis 2 reduziu a variância ambiental, mas alterou as estimativas da variância genotípica e o ordenamento dos genótipos, o que pode induzir a conclusões equivocadas na seleção. Embora a covariável "lateral" tenha sido influente na competição, o efeito em parcelas de cinco sulcos é pequeno.The objective of this work was to study different competition covariates in neighborhood analysis and to check the efficiency of this analysis in the increase of the experimental precision and the consequences in the ranking of sugarcane genotypes in terms of productive potential. Data used were from the state experimental network of the sugarcane breeding program installed in 2002, of the Instituto Agronômico, Campinas, SP, Brazil. The experimental design was in randomized complete blocks, with three replicates. The plots were formed of five 8 m rows with 1.5-m spacing between rows. The stalk productivity (TCH, Mg ha-1) was evaluated in the first and third harvests. The covariates "side", "tip" and "4 neighbors" were included in the Papadakis method and in two variations of the moving average method. The Papadakis and moving average 1 methods did not change the experimental precision in comparison with traditional analysis. The moving average 2 method reduced the environmental variance. However, it changed the estimates of the genetic variance and the genotype ranking, and could lead to erroneous conclusions in the selection. Although the "side" covariate was influential on competition, its effect or on five row-plots was small

EVALUATION OF COMPETITION EFFECT IN Eucalyptus PROGENY TESTS

Muitos estudos t\ueam recomendado o uso de parcelas pequenas na experimenta\ue7\ue3o florestal, por\ue9m, n\ue3o consideram o aumento da competi\ue7\ue3o intergenot\uedpica que isto acarreta e que pode resultar na sele\ue7\ue3o incorreta dos materiais gen \ue9ticos. O objetivo deste trabalho foi o de avaliar sete covari\ue1veis de competi\ue7\ue3o sobre o car\ue1ter volume de madeira em dois testes de prog \ueanies de Eucalyptus spp. O delineamento utilizado foi de blocos casualizados, com seis repeti\ue7\uf5es de 10 plantas. As sete covari\ue1veis analisadas foram \uedndice de competi\ue7\ue3o de Hegyi (IC), autocompeti\ue7\ue3o (AT), alocompeti\ue7\ue3o (AL), m\ue9dia da autocompeti\ue7\ue3o (MAT), m\ue9dia da alocompeti\ue7\ue3o (MAL) e m\ue9dia aritm \ue9tica dos quatro (M4) e oito vizinhos mais pr\uf3ximos (M8). Essas covari\ue1veis foram avaliadas individualmente bem com em todas as suas poss \uedveis combina\ue7\uf5es, obtendo-se estimativas de componentes de vari \ue2ncias e suas altera\ue7\uf5es com o emprego das mesmas. A competi\ue7\ue3o influenciou os resultados de an\ue1lises de testes de prog \ueanies de eucalipto, em que, autocompeti\ue7\ue3o e alocompeti\ue7\ue3o interferem de forma diferenciada. As covari\ue1veis mais influentes s\ue3o a MAT, a MAL e o IC. A rotina de an\ue1lise que apresentou melhores resultados foi a que incluiu as covari\ue1veis IC/MAT, sendo eficiente na redu\ue7\ue3o do efeito competicional em testes de prog \ueanies de eucalipto.Many studies have recommended the use of small plots for forest experiments, although they do not consider the inter-genotype competition increase. If this competition is not isolated from the mathematics model, it can lead to incorrect selection of genetic materials. The aim of this work was to evaluate the effect of seven competition covariates in two Eucalyptus spp. progeny tests. Data from the two half-sib eucalyptus progenies were analyzed, using the randomized blocks design. The seven analyzed covariates were HegyI\u2019s competition index (IC), self-competition (AT), alo competition (AL), self-competition mean (MAT), alo competition mean (MAL), and arithmetic means of four (M4) and eight (M8) nearest neighbors. Individual and combined analyses of covariates were used for the wood volume trait. All the variance components and the changes caused by covariates use were evaluated. The competition affects the results of eucalypt progeny analysis in different ways, according to its type, self or alo competition. Most influential covariates were MAT, MAL and IC. Most promising results of competition effects reduction were observed for the IC/ MAT covariates inclusion in eucalypt progeny tests

Modelos mistos na avaliação e ordenação de genótipos de cana-de-açúcar, com e sem efeitos de competição com parcelas vizinhas

Nos programas de melhoramento de cana-de-açúcar grande número de clones são avaliados todos os anos, em experimentos realizados em diferentes safras, épocas e regiões. E como é cada vez mais difícil selecionar os melhores genótipos fenotipicamente, o uso de métodos precisos de análise estatística é necessário, a fim de garantir maior confiabilidade ao processo seletivo. A avaliação genética com base em modelos mistos do tipo REML/BLUP (máxima verossimilhança restrita/ melhor predição linear não-viesada) tem merecido atenção especial dos pesquisadores. Outra questão importante durante o processo de seleção é a avaliação de possíveis efeitos da alocompetição sofrida pelos genótipos nos experimentos, pois, um genótipo em alocompetição pode ter comportamento diferente quando plantado comercialmente, apenas em autocompetição. Por essa razão, estratégias de análise que modelam a dependência espacial na forma de covariância, têm sido utilizadas no melhoramento com o objetivo de neutralizar os efeitos da competição entre parcelas vizinhas, além de aumentar a precisão experimental. Para o estudo desses fatores, foram utilizados dados de 1º e 3º corte, do atributo tonelada de cana/ha (TCH), da rede de ensaios estaduais do programa de melhoramento do Centro de Cana–IAC, instalados no ano de 2002. O delineamento experimental foi o de blocos casualizados com 3 repetições, sendo que a casualização em cada bloco foi feita uma única vez, de forma que em todos os experimentos, os genótipos tivessem sempre os mesmos vizinhos. As parcelas experimentais foram constituídas de cinco linhas de 8m espaçadas a 1,50m. De maneira geral, a análise por modelo misto e a análise tradicional apresentaram poucas diferenças em relação aos parâmetros avaliados e ao ordenamento dos genótipos, assim...In the programs for sugarcane improvement large number of clones are evaluated each year, in experiments realized in different crops, seasons and regions. And it is increasingly difficult to select the best genotypes phenotypically, the use of precise methods of statistical analysis is needed to ensure greater reliability in the selection process. The genetic evaluation based on mixed models of the type REML / BLUP (restricted maximum likelihood / best linear unbiased prediction) has deserved special attention from researchers. Another important issue during the selection process is the evaluation of possible effects of allocompetition suffered by the genotypes in the experiments, because a genotype in allocompetition may have different behavior when planted commercially, only in autocompetition. Therefore, strategies of analysis to model the spatial dependence in the form of covariance, have been used in improvement with the objective of neutralizing the effects of competition between neighboring plots, besides increasing the experimental precision. For the study of these factors, we used data from 1st and 3rd cuts, of the attribute tons of cane per hectare (TCH), than the network experiments state test of the improvement program of the Centro de Cana-IAC, Brazil, installed in 2002. The experimental design was a randomized block with 3 replications, with each block randomization was performed only once, so that in all experiments, the genotypes have the same neighbors. The experimental plots consisted of five lines of 8 m spaced to 1.50 m. In general, the mixed model analysis and traditional analysis showed little difference with respect to the parameters evaluated and the ranking of genotypes, as well as the use of different methodologies for the neighborhood analysis contributed little to increase the experimental precision. The effects of... (Complete abstract, click electonic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Breeding potential of maize composite Isanao VF1 in small spacing in the second growing season

The purpose of this study was to verify the breeding potential of the maize composite Isanao VF1 in the second growing season. One hundred and fifty half-sib progenies were evaluated of spacing of 0.45 m, densities of 57,778 and 80,000 plants ha(-1), in a randomized block design with three replications. Gains of 16.0 and 19.2% were estimated for grain Yield, H. I and 10.5% for prolificacy and 12.3 and 12.9% for ear height, respectively, at 57,778 and 80,000 plants ha(-1). The heritabilities for plant height, ear height and grain yield were 65.2 and 61.3%, 64.3 and 66.9% and 53.5 and 63.3%, respectively, confirming the potential for breeding at both densities. The absence of progeny by density interaction indicates that no further selection programs are necessary. The occurrence of segregation for modifier genes for height suggests stabilizing selection based on ear height