Divergência genética entre progênies de polinização aberta de Eucalyptus tereticornis Smith para caracteres de crescimento e tecnológicos da madeira
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2019-02-22
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Zanatto, Bruna
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Universidade Estadual Paulista (Unesp)
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O Eucalyptus tereticornis Smith tem boa adaptabilidade a diferentes regiões e resistência à seca, apresentando crescimento rápido e grande potencial de aplicação da madeira para diferentes usos. Neste sentido, o presente trabalho visou avaliar a divergência genética entre progênies de polinização aberta de E. tereticornis com base em caracteres de crescimento e tecnológicos da madeira. O experimento foi implantado no município de Luiz Antonio (SP), com 30 progênies de E. tereticornis, pertencentes a duas procedências, no delineamento experimental em blocos casualizados, parcelas de uma planta e 100 repetições, no espaçamento de 4 x 4 m. Com 31 anos de idade foram avaliados, em todo o ensaio, o diâmetro à altura do peito (DAP, cm), a altura total (m), sobrevivência (%) e forma do fuste. Foram abatidas três árvores representativas de cada progênie para determinações do volume e retirados discos em diferentes posições do fuste para a determinação da densidade básica (DBM), biomassa, teores de celulose (CEL), lignina (LIG), extrativos (EXT) e holocelulose (HOLO) na madeira. Os dados foram analisados pelo método REML/BLUP, obtendo-se estimativas de componente de variância e de parâmetros genéticos. Visando transformar o teste em um Pomar de Sementes por Mudas, foi simulada a seleção de 150 plantas (5%) para todos os caracteres, obtendo-se estimativas de ganhos genéticos e de tamanho efetivo (Ne). Adicionalmente, para o DAP outras duas estratégias de seleção foram simuladas: a seleção combinada entre e dentro de progênies e a seleção com restrição no número de indivíduos por família (n≤20). Nove caracteres, avaliados nas 90 árvores abatidas, foram submetidos a análise multivariada, pelo método hierárquico de agrupamento de Ward e não hierárquico de K-means e a análise de componentes principais. Os caracteres de crescimento apresentaram altos valores de herdabilidade ao nível de média de progênies, variando de 0,75 a 0,86. O coeficiente de variação relativa, que indica a razão entre o coeficiente de variação genotípico do indivíduo e o coeficiente de variação experimental variou de 0,37 a 0,79. As estimativas de herdabilidade ao nível de médias de progênies foram altas para CEL (0,65), EXT (0,53) e HOLO (0,43), reforçando que estes caracteres sofrem baixa influência ambiental. Estimativas medianas de herdabilidade foram obtidas para DBM (0,34) e LIG (0,29). Apesar da variabilidade genética entre as famílias de Eucalyptus tereticornis ser significativa, as expectativas de ganhos genéticos são pequenas, independentemente do caráter. A seleção de 5% dos melhores indivíduos, com base no valor genético individual, proporcionará baixo tamanho efetivo (Ne) entre os indivíduos selecionados. A seleção com restrição no número de indivíduos por família e a seleção entre e dentro de famílias, apesar de reduzirem ligeiramente as expectativas de ganho genético, aumentam o tamanho efetivo. Pelo método de Ward as progênies foram divididas em três grupos, sendo que os grupos 1 e 2, de maiores produtividades, diferenciaram pelos caracteres tecnológicos da madeira e o grupo 3, reuniu progênies de menor produtividade. No método de K-means, os três grupos formados diferenciaram pouco daqueles obtidos no método de Ward, porém os três grupos formados distinguiram melhor as progênies quanto à produtividade. Na análise por componentes principais, os três primeiros componentes explicaram 78,49% da variância contida nas variáveis originais. Conclui-se, portanto, que as 30 progênies de polinização aberta de Eucalyptus tereticornis, diferem quanto ao potencial produtivo e caracteres da madeira; é possível a seleção de progênies com bom potencial produtivo e com características divergentes quanto aos caracteres da madeira, que poderão ser usadas em programas de melhoramento com finalidades distintas.
Eucalyptus tereticornis Smith has good adaptability to different regions and drought tolerance, showing fast growth and great potential of application of the wood for multiple purposes. In this sense, the present work aimed to evaluate the genetic divergence among progenies of open pollination of E. tereticornis based on growth and wood technological characters. The experiment was carried out in Luiz Antonio (SP), with 30 progenies of E. tereticornis, belonging to two provenances, in the randomized blocks design, single tree plot and 100 replicates, at 4 x 4 m spacing. At 31 years old, the diameter at breast height (DAP, cm), total height (m), survival (%) and stem shape. Three representative trees of each progeny were harvested for determination of volume and discs were sampled at different positions of the stem for determination of wood basic density (DBM), biomass and wood contents of cellulose (CEL), lignin (LIG), extractive (EXT) and holocellulose (HOLO). The data were analyzed by the REML/BLUP method, obtaining estimates of variance component and genetic parameters. Aiming to transform the test into a Seed Orchard by Seedling, the selection of 150 plants (5%) for all traits was simulated, obtaining estimates of genetic gains and effective size (Ne). Additionally, for the DAP, two other selection strategies were simulated: the combined selection among and within progenies and the restricted selection in the number of individuals per family (n≤20). Nine characters, evaluated in the 90 harvested trees, were submitted to multivariate analysis, using the hierarchical method of Ward grouping and non-hierarchical K-means analysis and principal component analysis. The growth characteristics showed high heritability values at the level of progenies, ranging from 0.75 to 0.86. The relative coefficient of variation, which indicates the ratio between the genotypic coefficient of variation of the individual and the coefficient of variation ranged from 0.37 to 0.79. Heritability estimates at the level of progeny averages were high for CEL (0.65), EXT (0.53) and HOLO (0.43), reinforcing that these characters are under low environmental influence. Median heritability estimates were obtained for DBM (0.34) and LIG (0.29). Although genetic variability among Eucalyptus tereticornis families is significant, expectations for genetic gains are small, regardless of character. The selection of 5% of the best individuals, based on the individual genetic value, will provide a low Ne among the selected individuals. Selections with restriction on the number of individuals per family or selection among and within families, although slightly reducing genetic gain expectations, increase the Ne. By the Ward method the progenies were divided into three groups, and groups 1 and 2, with higher yields, differentiated by the wood technological characteristics and group 3, brought together progenies of lower productivity. In the K-means method, the three groups formed differed little from those obtained in the Ward method, but presented better defined characteristics with the formation of three groups, as well as productivity. In the principal component analysis the first three components explained 78.49% of the variance contained in the original variables. It is concluded that the 30 progenies of open pollination of Eucalyptus tereticornis, differ in the productive potential and wood traits; it´s possible to select progenies with good productive potential and with divergent technological wood characters, which can be used in breeding programs with different purposes.
Eucalyptus tereticornis Smith has good adaptability to different regions and drought tolerance, showing fast growth and great potential of application of the wood for multiple purposes. In this sense, the present work aimed to evaluate the genetic divergence among progenies of open pollination of E. tereticornis based on growth and wood technological characters. The experiment was carried out in Luiz Antonio (SP), with 30 progenies of E. tereticornis, belonging to two provenances, in the randomized blocks design, single tree plot and 100 replicates, at 4 x 4 m spacing. At 31 years old, the diameter at breast height (DAP, cm), total height (m), survival (%) and stem shape. Three representative trees of each progeny were harvested for determination of volume and discs were sampled at different positions of the stem for determination of wood basic density (DBM), biomass and wood contents of cellulose (CEL), lignin (LIG), extractive (EXT) and holocellulose (HOLO). The data were analyzed by the REML/BLUP method, obtaining estimates of variance component and genetic parameters. Aiming to transform the test into a Seed Orchard by Seedling, the selection of 150 plants (5%) for all traits was simulated, obtaining estimates of genetic gains and effective size (Ne). Additionally, for the DAP, two other selection strategies were simulated: the combined selection among and within progenies and the restricted selection in the number of individuals per family (n≤20). Nine characters, evaluated in the 90 harvested trees, were submitted to multivariate analysis, using the hierarchical method of Ward grouping and non-hierarchical K-means analysis and principal component analysis. The growth characteristics showed high heritability values at the level of progenies, ranging from 0.75 to 0.86. The relative coefficient of variation, which indicates the ratio between the genotypic coefficient of variation of the individual and the coefficient of variation ranged from 0.37 to 0.79. Heritability estimates at the level of progeny averages were high for CEL (0.65), EXT (0.53) and HOLO (0.43), reinforcing that these characters are under low environmental influence. Median heritability estimates were obtained for DBM (0.34) and LIG (0.29). Although genetic variability among Eucalyptus tereticornis families is significant, expectations for genetic gains are small, regardless of character. The selection of 5% of the best individuals, based on the individual genetic value, will provide a low Ne among the selected individuals. Selections with restriction on the number of individuals per family or selection among and within families, although slightly reducing genetic gain expectations, increase the Ne. By the Ward method the progenies were divided into three groups, and groups 1 and 2, with higher yields, differentiated by the wood technological characteristics and group 3, brought together progenies of lower productivity. In the K-means method, the three groups formed differed little from those obtained in the Ward method, but presented better defined characteristics with the formation of three groups, as well as productivity. In the principal component analysis the first three components explained 78.49% of the variance contained in the original variables. It is concluded that the 30 progenies of open pollination of Eucalyptus tereticornis, differ in the productive potential and wood traits; it´s possible to select progenies with good productive potential and with divergent technological wood characters, which can be used in breeding programs with different purposes.
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Análise multivariada, Qualidade da madeira, Melhoramento florestal