Efeito competicional em testes de progênies de eucalipto

Abstract

RESUMOMuitos estudos têm recomendado o uso de parcelas pequenas na experimentação florestal, porém, não consideram o aumento da competição intergenotípica que isto acarreta e que pode resultar na seleção incorreta dos materiais genéticos. O objetivo deste trabalho foi o de avaliar sete covariáveis de competição sobre o caráter volume de madeira em dois testes de progênies de Eucalyptus spp. O delineamento utilizado foi de blocos casualizados, com seis repetições de 10 plantas. As sete covariáveis analisadas foram índice de competição de Hegyi (IC), autocompetição (AT), alocompetição (AL), média da autocompetição (MAT), média da alocompetição (MAL) e média aritmética dos quatro (M4) e oito vizinhos mais próximos (M8). Essas covariáveis foram avaliadas individualmente bem com em todas as suas possíveis combinações, obtendo-se estimativas de componentes de variâncias e suas alterações com o emprego das mesmas. A competição influenciou os resultados de análises de testes de progênies de eucalipto, em que, autocompetição e alocompetição interferem de forma diferenciada. As covariáveis mais influentes são a MAT, a MAL e o IC. A rotina de análise que apresentou melhores resultados foi a que incluiu as covariáveis IC/MAT, sendo eficiente na redução do efeito competicional em testes de progênies de eucalipto. Palavras-chave: Eucalyptus spp.; competição intergenotípica; famílias de polinização aberta. ABSTRACTMany 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's 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.

PHENOTYPIC MODELS OF COMPETITION FOR Pinus taeda L GENETIC PARAMETERS ESTIMATION

“…Arithmetic mean of the silvicultural characteristic of the alo competitive trees (PAVAN et al, 2012), belonging to different genetic material (equation 8), where Y j is the observed value of the alo competitive plant j and n the number of alo competitive plants.…”

“…In forest field trials, it is mainly caused by the lack of space induced by high intraspecific density (LEONARDECZ-NETO et al, 2003). In which the growth of the individuals of the plot is correlated to its neighbors, due to the common micro environment (PAVAN et al, 2012). In linear plots, this competition can occur within the plots (inter-genotypic competition) or between the experimental plots (intragenotypic competition).…”

“…However, in the models used for analysis of progeny tests, it is not common to consider the effects of competition, as there are no established routines; and the definition of specific methods to correct this type of interference (PAVAN et al, 2012), this implies in the reduction of the ability to identify the genetic variation and the precision of the genetic value prediction (YE and JAYAWICKRAMA, 2008).…”

“…Using simulated modeling data and Cappa and Cantet (2008) in P. taeda tests at 13 years of age using models that incorporate competition for both, genetic and non-genetic levels. Phenotypic models were studied by Leonardecz-Neto et al (2003), who used Hegyi competition index for DBH data in several forest species and Pavan et al (2012), using besides this index other six covariates in Eucalyptus progenies tests for volume. The DBH and volume variables are more influenced by spacing and more susceptible to competition effects than the height (YE and JAYAWICKRAMA, 2008;STOEHR et al, 2010).…”

“…However, knowing which covariant and how it fits to faithfully represent, the biological effect, is often unknown (PAVAN et al, 2012). One way to diagnose the presence of competition effects in field trials is from the residual correlation coefficient in which competition effects between neighboring plants cause negative autocorrelation and spatial heterogeneity causes positive correlations CAPPA et al, 2016).…”