SYNOPSIS The interspecific hybrid between P. elliottii var. elliottii and P. caribaea var. hondurensis has recently been accepted for planting operationally as an alternative to P. elliottii by Sappi in South Africa. Some concerns have been expressed as to the suitability of the hybrid for the production of pulpwood; these stein from the observed inferiority of P. caribaea var. hondurensis, one of tile parents of this hybrid, as a source of pulpwood in South Africa. As part of a collaborative project with the Queensland Forestry Research Institute (QFRI) in Australia, who felled and supplied chips from 4 individual trees of a suitable age of each of 4 families of each taxon. The kraft pulp yield and pulp properties of P. elliottii var. elliottii and the P. elliottii x P. caribaea var. hondurensis hybrid were compared using laboratory scale pulping. Keywords: P. elliottii var elliottiiP. caribaea var. hondurensis hybrid kraft pulping laboratory scale pulping pulp yield wood density kappa burst tear
Tree breeding has resulted in significant genetic improvement of several forest tree species during the 30 years of its intensive application. This has been achieved principally through population improvement (seed orchards) and a few cases each of hybridization and mass clonal propagation. Current prospects for both interspecific and interprovenance hydridization are good because of greater knowledge and improved technology. Methods for mass-producing hybrid material are described. Special mention is made of the use of hybridization to develop synthetic populations incorporating desirable gene complexes from a number of sources. The concept of provenance seedling seed orchards is endorsed, and it is recommended that clonal orchards of this type be established also. There has also been a near explosion of interest in the old technique of clonal propagation, using new methods and technology. Clonal propagation is very attractive because of its use of almost all the genetic variation, and because of the short time between application and realization. There are difficult problems remaining for clonal propagation of many species; nevertheless, it is likely that increasing and highly rewarding effort will be invested in this approach, especially in combination with hybridization. Actual genetic gains realized are conditioned by response of the genetic materialmore » to the environment. Hence genotype-by-environment interaction (GxEI) is coming under scrutiny. A popular approach is to attempt to identify broadly adapted genotypes with relatively high yields over a wide range of environments. Prospects seem better in some species, however, for positive use of this extra source of variation through subdivision of operational units into uniform strata and allocation of appropriate genertic material thereto, so that the optimum combination, in economic and ecological terms, is achieved. (Refs. 116).« less
Genetic parameters were estimated for height, diameter, stem straightness, internode length and wood density between five and 16 years after planting in four open-pollinated progeny tests of hoop pine in south-east Queensland
Abstract In Australia, there has been rapid expansion in recent years of commercial plantations of hardwood timber species, especially of Eucalyptus and Corymbia. In tropical and sub-tropical Queensland the land most likely to be readily available for this planting is in the marginal 650-1000 MAR zone where, potentially, millions of hectares could be planted on cleared land. Optimal forestry plantation practice requires matching of taxa (species-provenances-hybrids) and sites. However, experiment-based identification of taxa with commercial potential has not been accomplished for many regions in this rainfall zone of Queensland. In Brazil, China and South Africa, large viable plantation estates have been developed on marginal lands through use ofhardy, high-yielding interspecific eucalypt hybrids (Eldridge et al. 1993). Eucalypt hybrid breeding is in its infancy in Queensland so the potential exists to accelerate the identification of superior hybrids through introduction and testing ofmaterial developed elsewhere. Based on this overseas experience, bulk seedlots of selected eucalypt hybrids have been introduced, in strict accordance with quarantine requirements, and are now being tested against Eucalyptus and Corymbia species and provenance controls in key regions of Queensland and northern NSW. This paper presents two-year results for three trials in sub-tropical Queensland, indicates the taxa with fastest early growth and considers the potential and suitability of several eucalypt hybrids (seedlings) to marginal sites in Queensland. Keywords: Eucalyptus hybridstaxa trialsmarginal landssite matching
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