Genetic Improvement of Timber Yield and Wood Quality in<i>Eucalyptus Grandis</i>(Hill) Maiden

Wyk, G. van

doi:10.1080/00382167.1990.9629025

Cited by 10 publications

(11 citation statements)

References 6 publications

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“…The relatively high dominance variance present in our study also provides an opportunity to increase genetic gains by propagating families with superior growth vegetatively (Van Wyk 1990). The phenomenon of relatively high dominance variance in an E. grandis full-sib population in South Africa was also reported in the studies conducted by Van Wyk (1990) and Retief and Stanger (2009).…”

Section: Discussionmentioning

confidence: 48%

“…The phenomenon of relatively high dominance variance in an E. grandis full-sib population in South Africa was also reported in the studies conducted by Van Wyk (1990) and Retief and Stanger (2009). Such families could be reproduced through repeat-controlled pollinations and resultant seedlings can be vegetatively propagated for either commercial production or to enrich the breeding population with superior genotypes.…”

Section: Discussionmentioning

confidence: 77%

“…In forests tree breeding, the best fullsib families would often be expected from the parents with the highest general combining abilities (Cotteril et al 1987). Van Wyk (1990) reported a good correlation between BV and observed genotypic values for an E. grandis full-sib population. Cotteril et al (1987) reported similar results for full-sib pine trials in South Africa.…”

Section: Discussionmentioning

confidence: 98%

“…Eucalyptus grandis Hill ex Maiden is one of the main species planted either as a pure species crop, or as an inter-specific hybrid crop. The fast growth of E. grandis and the general suitability of its timber for a range of products are the main reasons for the large demand for E. grandis (Van Wyk 1990). However, E. grandis is susceptible to fungal diseases like Crysoporthe austroafricana and Coniothyrium sp.…”

Section: Introductionmentioning

confidence: 99%

“…Some information on genetic parameters of E. grandis populations in South Africa is available (van Wyk 1990;Pierce 2000;Snedden and Verryn 2004;Snedden et al 2007;Retief and Stanger 2009). …”

Section: Introductionmentioning

confidence: 99%

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Genetic parameters and genotype by environment interaction ofEucalyptus grandispopulations used in intraspecific hybrid production in South Africa

Berg

Verryn

Chirwa

et al. 2016

Southern Forests: a Journal of Forest Science

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In South Africa, Eucalyptus grandis is an important species due to its fast growth and general sustainability of its timber for a range of products. However, E. grandis is susceptible to fungal diseases like Crysoporthe austroafricana and Coniothyrium sp.cankers in the sub-tropical region of Zululand and is therefore mainly planted as a parental species in a hybrid combination with E. urophylla in this region. The current strategy is to maintain large breeding populations of both parental species in order to provide improved elite selections for hybrid crosses. In order to develop the best interspecific hybrid breeding strategy for E. grandis, it is important to first determine estimates of genetic parameters of the pure species parents. Estimating the genotype by 2 environment interaction (GxE) is also necessary in proposing the basis for setting up breeding populations and selecting environmentally stable genotypes. With this in mind, two E. grandis full-sib progeny trials were planted in Zululand and one in the KwaZuluNatal Midlands region. The aims of this study were firstly to determine the magnitude of GxE of E. grandis across the three sites; secondly to estimate the genetic parameters for growth of the E. grandis parents selected for intra-specific crosses; and lastly to identify the best parents to use for intra-and inter-specific crosses in future hybrid breeding programmes.Results of our study indicated that GxE would be practically negligible for growth in Zululand and one group of elite parents can be used for hybrid crosses in this region. In general, growth traits were under low to moderate genetic control, and the variation in additive genetics enabled us to identify E. grandis parents that could be utilised for intraspecific crosses and deliver progeny with genetic gains of 28.4%. Our study also highlighted that a relatively large portion of the genetic variation was explained by dominance genetic variation and a strategy to capture this non-additive variation needs investigation.Although our study as achieved the stated aims, it must be kept in mind that E. grandis is mainly used as a hybrid parent with E. urophylla in Zululand. A study to investigate whether the parents with good GCA values from our study are also good general combiners in inter-specific hybrid combinations with E. urophylla needs to be conducted.

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Section: Discussionmentioning

confidence: 48%

Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Genetic parameters and genotype by environment interaction ofEucalyptus grandispopulations used in intraspecific hybrid production in South Africa

Berg

Verryn

Chirwa

et al. 2016

Southern Forests: a Journal of Forest Science

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Age–age and trait–trait correlations for Eucalyptus grandis Hill ex Maiden and their implications for optimal selection age and design of clonal trials

2003

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Previous results from seven locations of Eucalyptus grandis clonal trials in Colombia supported the a priori contention of sub-dividing them into three different environmental zones for testing and deployment. Within these zones, the determination of age-age genetic correlations for both height and mean annual increment (MAI) showed that strong age-age correlations are present for a rotation age of 6 years starting at 3 years age and, thereafter, suggesting this age as appropriate for selection. This biological selection age coincides with an "economical" age for selection based on discounted selection efficiency in perpetuity, considering a range of interest rates between 10% and 20%. High genetic correlations between wood density at 3 years and 6 years as well as the lack of genetic correlation between this trait and growth traits, also favors selection at age 3 and facilitates breeding strategies that consider the utilization of both traits for improvement. A simulation of optimal clonal test designs indicated that by using six locations and six blocks per location in a single-tree plot design, between 80% and 90% of the maximum selection efficiency could be obtained. This type of design allows testing of a large number of genotypes across a reasonable number of locations in a cost-effective manner.

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Trends in additive, dominance and environmental effects with age for growth traits in Eucalyptus hybrid populations

2008

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Expression of additive and dominance effects during development of forest trees species is poorly documented. A set of 10 subpopulations, generated from factorial mating amongst subsets of 88 females and 107 males representing 684 families and 37,206 individual trees, was used to estimate variance components between 4 and 65 months in a Eucalyptus urophylla * grandis breeding population. The variance components were significantly different from zero for female, male and female-by-male interaction effects for height and circumference. The results, from the set of experiments, stressed the huge dispersion of variance component estimates among subpopulations. The trends were modelled using linear and nonlinear models. The trends in additive, dominance and environmental variances with age showed three phases corresponding to the stage of competition during stand development. No significant trend was observed for the coefficients of variation of these three effects. The dominance to additive variance ratio did not show specific age-related trends and was close to 1.2 during the growth period. The additive, dominance and environmental correlations between height and circumference were higher than 0.8 after 24 months. A similar age-related trend was observed for the additive and dominance effects. These results emphasise the significant role of dominance in the genetic control of growth traits. They differ from the majority of studies of pines, where additive variance is preponderant, but are similar to those of other eucalyptus studies. In the context of Congolese breeding strategy, this can be explained by the phenotypic selection of parents constituting the breeding population and/or the expression of overdominance in eucalyptus hybrid populations planted in marginal zones.

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Genetic Improvement of Timber Yield and Wood Quality inEucalyptus Grandis(Hill) Maiden

Cited by 10 publications

References 6 publications

Genetic parameters and genotype by environment interaction ofEucalyptus grandispopulations used in intraspecific hybrid production in South Africa

Genetic parameters and genotype by environment interaction ofEucalyptus grandispopulations used in intraspecific hybrid production in South Africa

Age–age and trait–trait correlations for Eucalyptus grandis Hill ex Maiden and their implications for optimal selection age and design of clonal trials

Trends in additive, dominance and environmental effects with age for growth traits in Eucalyptus hybrid populations

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