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

Número de repetições, de plantas por parcela e de avaliações para testes clonais de eucalipto

The objective of this work was to determine the necessary number of replicates, of plants per plot, and of measurements for evaluating growth traits in eucalyptus (Eucalyptus spp.) clonal tests. Data on height, diameter at breast height, and wood volume were evaluated in three clonal tests, performed in a randomized complete block design with 30 (tests 1 and 2) and 10 clones (test 3), with six replicates of six (test 1) and 10 (tests 2 and 3) plants. The evaluations were performed from 14 to 74 months of age. The coefficients of repeatability and determination were estimated, as well as the effects of increasing measurement frequency on selective efficiency. Wood volume is the trait with the greatest variability in the plot and the lowest repeatability; therefore, it requires more plants to obtain high accuracy in the estimate of the individual’s true value. In Eucalyptus grandis x E. urophylla hybrid clonal tests, the use of three replicates of six plants per plot and of three evaluations, at ages above 2 years, is recommended in order to achieve a selective accuracy around 90%.O objetivo deste trabalho foi determinar o número de repetições, de plantas por parcela e de medições necessário para avaliação de caracteres de crescimento em testes clonais de eucalipto (Eucalyptus spp.). Foram avaliados dados de altura, diâmetro à altura do peito e volume de madeira, em três testes clonais, realizados em delineamento de blocos ao acaso, com 30 (testes 1 e 2) e 10 clones (teste 3), com seis repetições de seis (teste 1) e de 10 (testes 2 e 3) plantas. As avaliações foram realizadas dos 14 aos 74 meses de idade. Foram estimados os coeficientes de repetibilidade e de determinação, bem como os efeitos do acréscimo na frequência das medições sobre a eficiência seletiva. O volume de madeira é a característica com maior variabilidade na parcela e menor repetibilidade; portanto, exige maior número de plantas para que se obtenha elevada exatidão na estimativa do valor real do indivíduo. Em testes clonais de híbridos de Eucalyptus grandis x E. urophylla, recomenda-se o uso de três repetições, com seis plantas por parcela, e de três avaliações, em idades superiores a 2 anos, para que se alcance acurácia seletiva em torno de 90%

Early selection viability in Eucalyptus spp clonal tests

Com o objetivo de avaliar a efici\ueancia da sele\ue7\ue3o precoce em Eucalyptus spp. foram usados dados de dois testes clonais avaliados quanto ao crescimento em altura (ALT), di\ue2metro \ue0 altura do peito (DAP) e volume individual de madeira (VOL) aos 25, 50 e 72 meses de idade. O delineamento experimental nos dois testes clonais foi o de blocos casualizados, com trinta tratamentos (clones), seis repeti\ue7\uf5es, sendo um deles com seis e o outro com dez plantas em linha por parcela, no espa\ue7amento de 3,0 m x 3,0 m. Foi feita a an\ue1lise de vari\ue2ncia para cada caracter e idade. Foram obtidas as estimativas de coeficiente de determina\ue7\ue3o genot\uedpico e de correla\ue7\uf5es genot\uedpicas entre os caracteres nas idades juvenis e na idade de rota\ue7\ue3o. Para verificar a viabilidade da aplica\ue7\ue3o da sele\ue7\ue3o precoce, foi simulada a sele\ue7\ue3o de 30% dos clones nas idades juvenis e na idade de rota\ue7\ue3o para cada um dos caracteres e idades avaliadas, obtendo-se as estimativas de ganhos gen\ue9ticos com a sele\ue7\ue3o direta e indireta. Houve diferen\ue7as significativas entre os clones avaliados nos dois experimentos para todos os caracteres e idades. Com base nos resultados obtidos, \ue9 poss\uedvel efetuar a sele\ue7\ue3o precoce aos 2 anos de idade sobre o caracter DAP em testes clonais de eucalipto.With the aim of evaluating Eucalyptus spp. for early selection efficiency, the height (HGT), diameter at breast height (DBH) and individual wood volume (VOL) of two clonal tests were assessed at the ages of 25, 50, and 72 months. The experimental design consisted of randomized blocks, containing 30 treatments (clones), 6 replications and linear plots, one of them with 6 plants and the other with 10 plants, at the spacing of 3.0m x 3.0m. Variance analysis for each trait and age were carried out in the trials. The estimates of genotypic determination coefficient and the correlation between the early and mature ages for each trait were obtained. In order to confirm the viability of early selection, a simulated selection was performed at young and mature ages, adopting 30% of selection proportion for each trait and age considered. The genetic gains were estimated by using both direct and indirect selection. There were significant differences among clones evaluated in the two experiments for all traits and ages. Based on the results obtained for DBH in eucalyptus clonal tests, the use of early selection at the age of 2 years is feasible

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

Seleção precoce em famílias de polinização aberta de Eucalyptus com base em covariáveis de competição

The objetive of this work was to evaluate the influence of intergenotypic competition in open‑pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria.O objetivo deste trabalho foi avaliar a influência da competição intergenotípica em famílias de polinização aberta de Eucalyptus e o seu efeito na eficiência da seleção precoce. Foram realizados dois experimentos, nos quais o volume de madeira foi avaliado em três idades, em delineamento de blocos ao acaso. Dados dos três anos de avaliação (experimento 1, aos 2, 4 e 7 anos; e experimento 2, aos 3, 5 e 7 anos) foram analisados a partir de modelos mistos. Foram estimados: componentes de variância, parâmetros genéticos, ganhos com a seleção, número efetivo, eficiência da seleção precoce, ganho com a seleção por unidade de tempo e coincidência de seleção com e sem uso de covariáveis de competição. O efeito da competição não foi significativo em idades inferiores a três anos, e o ajuste por covariáveis de competição foi desnecessário. A seleção precoce para famílias é eficiente; famílias de hábitos de crescimento tardio são mais vulneráveis à competição, o que prejudica de forma mais pronunciada a sua classificação ao final do ciclo. A seleção precoce mostra-se eficiente de acordo com todos os critérios adotados, e a idade em torno de três anos é a mais recomendada, em razão da alta eficiência e do alto índice de acerto na indicação de árvores e famílias. A adição de covariáveis de competição ao final do ciclo melhora a eficiência da seleção precoce para quase todos os critérios estudados

Early selection in open-pollinated Eucalyptus families based on competition covariates

The objetive of this work was to evaluate the influence of intergenotypic competition in open-pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria