Eucalyptus breeding to obtain clones for the cellulose industry / Melhoramento de eucalipto visando à obtenÃÃo de clones para a indÃstria de celulose

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The objectives of this study were to determine the potential of different alternatives for obtaining Eucalyptus clones that could surpass the current ones in cellulose production, as well as to obtain useful information for breeding programs. Three researches were carried out. In the first the objective was to estimate the inbreeding depression in commercial clones and to check if it is possible to obtain F2 individuals with a superior performance to their F1 generation. For this, the clonal (F1) and inbred (F2) generations were evaluated in two contiguous experiments, carried out in Aracruz, EspÃrito Santo State, Brazil. A randomized complete block design with single plant plots and 40 replicates was used in both experiments. The objective of the second research was to introgress alleles from species that have better wood quality to increase cellulose productivity in crossings with E. grandis and E. urophylla or their hybrids. To do so, 44 hybrid combinations between six elite clones from Aracruz Celulose S. A. with ten E. camaldulensis and 47 hybrid combinations between the same six elite clones with ten E. globulus clones were evaluated. The hybrid combinations were obtained by means of two half-diallel mating designs. The resulting hybrid combinations as well as the four check clones were evaluated in two experiments, one for each diallel. Both experiments were carried out in three sites, Aracruz and SÃo Mateus, in the EspÃrito Santo State, and Caravelas, Bahia State, Brazil, in a randomized complete block design with single plant plots and 40 replicates. The third work aimed at verifies if the reciprocal recurrent selection had any advantage over the recurrent selection for the improvement of the circumference at breast height and wood basic density. Sixty-two half-sib families of E. grandis, 68 half-sib families of E. urophylla, 50 full-sib families of E. grandis x E. urophylla, plus four checks were evaluated. The experiment was carried out in the same locations as for the previous research, using a 14 x 14 lattice design, with single plant plots and 40 replicates. In all three cases, two years following the planting, the circumference at breast height and the wood basic density were measured. It was concluded that the inbreeding depression varied among clones and it had an average of 17.5% for the circumference at breast height and 4.0% for the wood basic density. In most cases it was possible to select F2 trees with a higher performance than that of their (F1) parents, showing that this is a good strategy for breeders to select superior plants. The diallel crossings were promising both for the wood volume and wood quality gain. The general combining ability was responsible for most of the variations between the hybrids. As for the elite clones, the most appropriate tester varied according to each species used and with the trait being evaluated. The circumference at breast height showed high heterosis, indicating genetic divergence between the E. grandis and E. urophylla families, and also that dominance control this character. Thus, the reciprocal recurrent selection should be used as a strategy for breeding programs aiming a high wood volume. The heterosis was close to zero for the wood basic density. Since there was divergence between the parents, it can be inferred that dominance has no importance for this character. Consequently, the recurrent selection is the most appropriate if the selection is made only for the wood basic density. The negative correlation between the circumference at breast height and the wood basic density could impair the simultaneous selection for both characters, depending on the wood basic density range used by the industry.

ASSUNTO(S)

endogamia diallel crosses eucalyptus wood basic density quantitative genetics circunferÃncia à altura do peito recurrent selection circumference at breast height inbreeding seleÃÃo recorrente cruzamento dialÃlico densidade bÃsica da madeira genetica e melhoramento florestal eucalyptus genÃtica quantitativa

ACESSO AO ARTIGO

Documentos Relacionados