Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to ... more Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to supplement native forest ‘ash ’ eucalypt logs for the Tasmanian sawmilling industry. Processing methods developed for native forest euca-
The first Europeans to discover Eucalyptus globulus were French explorers in 1792. Its seed was r... more The first Europeans to discover Eucalyptus globulus were French explorers in 1792. Its seed was rapidly spread throughout the world in the 19th century and this was the species by which much of the world first knew the genus. However, it was in the industrial forests of the 20th century that this species, once considered the ‘Prince of Eucalypts’, achieved greatest prominence due to its fast growth and superior pulp qualities. Formal breeding first commenced in 1966 in Portugal and in the late 1980’s large base population trials from open-pollinated seed collections from native stands were established in many countries. These trials have provided
Effective nutrition management is vital for optimising productivity in many eucalypt plantations,... more Effective nutrition management is vital for optimising productivity in many eucalypt plantations, to protect the large investment in pruning for solid wood production and meet long-term woodflow targets. A fertiliser decision support tool, EucFERT, has been developed which is helping forest managers to maximise growth responses while being economic and minimising off-site nutrient losses. The tool uses detailed local soil information along with crop and site data to provide guidance on a stand basis. Predicted growth responses to fertiliser are based on long-term nutrition experiments covering early-rotation and mid-rotation trials across a range of site and soil types. Outputs from EucFERT can be used to prepare Stand fertiliser management plans that include soil and site management, fertiliser product, rate, application, frequency and timing, along with environmental and operational cautions relating to aerial application. The use of this computerised tool provides much greater co...
Forty-nine provenances from a rangewide collection of Eucalyptus regnans F. Muell were establishe... more Forty-nine provenances from a rangewide collection of Eucalyptus regnans F. Muell were established at each of 12 sites throughout its natural distribution. Trees on the nine surviving sites were assessed for diameter at breast height, stem straightness and branching quality at ages between 9 and 13 years. Provenance differences were found at each site but genotype by environment interactions were also significant. Provenance rankings differed between sites and no single provenance or group of provenances was found to be among the best for all traits at all sites. Several provenances (Mt Useful, Quarry Creek. Buchan, Otway Messmate and New I-Iaven) were consistently amongst the worst for growth at all sites. For stem straightness Narbethong was outstanding, ranking highly across all sites, whereas Lavers Hill, Christmas Hills and Strathblane were consistently amongst the worst. Local provenances did not perform amongst the best at eight out of the nine sites. Provenances collected fr...
Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protec... more Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protección de los bosques naturales. Como resultado, los productores de maderas de alto valor han dirigido su interés a las plantaciones de Eucalyptus como una fuente para el suministro de madera de latifoliadas que tradicionalmente se obtenía de bosques naturales. Varias especies de Eucalyptus se han establecido
Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to ... more Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to supplement native forest 'ash' eucalypt logs for the Tasmanian sawmilling industry. Processing methods developed for native forest euca-lypts were applied to logs from 22-year-old pruned stands thinned at age six years to 100, 200, 300, 400 stems/ha and unthinned control stands with a stocking of 700 stems/ha at harvest. Consistent with existing industry requirements for the two sawing methods, 42 trees with diameter at breast height over bark (DBHOB) < 43 cm were selected for back-sawing (fl at-sawing), and 39 trees with DBHOB > 43 cm for quarter-sawing. For each sawing method, sets of trees were selected to provide trees evenly distributed across the target diameter range and, as near as possible, with sets matched across thinning treatments for size. From each tree two sawlogs, nominally 2.7 m in length, were cut from the pruned part of the stem. Both logs from individua...
Primeros resultados de un ensayo de severidad de poda en Eucalyptus regnans: efectos 1 en el crec... more Primeros resultados de un ensayo de severidad de poda en Eucalyptus regnans: efectos 1 en el crecimiento y respuesta fisiológica. 2 Peter 3 4 5 6 7 RESUMEN 8 Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protección 9 de los bosques naturales. Como resultado, los productores de maderas de alto valor han dirigido su 10 interés a las plantaciones de Eucalyptus como una fuente para el suministro de madera de latifoliadas 11 que tradicionalmente se obtenía de bosques naturales. Varias especies de Eucalyptus se han establecido 12 en diversos países desde los trópicos hasta las zonas de clima templado frío. Una especie de interés en 13 la zona fría y templada, es E. regnans, que se ha establecido con éxito en Nueva Zelanda y Chile. En su 14 medio natural, los bosques esclerófilos húmedos del sureste de Australia, puede alcanzar alturas 15 cercanas a 100 metros y es una de las maderas más populares para una amplia gama de productos, 16 incluidos ...
Effective nutrition management is vital for optimising productivity in many eucalypt plantations,... more Effective nutrition management is vital for optimising productivity in many eucalypt plantations, to protect the large investment in pruning for solid wood production and meet long-term woodflow targets. A fertiliser decision support tool, EucFERT, has been developed which is helping forest managers to maximise growth responses while being economic and minimising off-site nutrient losses. The tool uses detailed local soil information along with crop and site data to provide guidance on a stand basis. Predicted growth responses to fertiliser are based on long-term nutrition experiments covering early-rotation and mid-rotation trials across a range of site and soil types. Outputs from EucFERT can be used to prepare Stand fertiliser management plans that include soil and site management, fertiliser product, rate, application, frequency and timing, along with environmental and operational cautions relating to aerial application. The use of this computerised tool provides much greater co...
The photosynthetic response to pruning was measured in two Eucalyptus regnans stands, aged 2 and ... more The photosynthetic response to pruning was measured in two Eucalyptus regnans stands, aged 2 and 3 years, located in areas of high productivity on the coast of the province of Arauco, Chile. Variables such as rates of CO 2 assimilation and stomatal conductance were measured in three ages of foliage on trees with different pruning severity treatments, which corresponded to the removal of 0 % (control), 30, 50 and 70 % of live crown length. The 2-year-old stand measurements were performed at the time of pruning and 6, 10, 14 and 18 weeks later, and the 3-year stand, 5, 9, 18 and 28 weeks after pruning. In both trials, significant differences were found between the foliage ages for all instances of measurement showing the mature foliage the highest values up to 30 % higher than old foliage. There were also significant differences between pruning severity treatments in both trials in which, in general, the highest values of CO 2 assimilation were observed among the highest pruning severity treatments with values up to 40 % higher than the unpruned trees.
... thinning operations open the canopy to wind penetration and can dramatically increase the vul... more ... thinning operations open the canopy to wind penetration and can dramatically increase the vulnerability of a stand to windthrow (Savill, 1983; Ruel, 1995; Quine ... The incidence of windthrow has been positively related to the rate of thinning (Ruth and Yoder, 1953; Booth, 1974). ...
Genetic improvement of wood properties affecting the quality of pulpwood and peeled veneer produc... more Genetic improvement of wood properties affecting the quality of pulpwood and peeled veneer products is of general interest to tree breeders worldwide. If the wood properties of Eucalyptus nitens (H. Deane & Maiden) Maiden are under genetic control and the correlations between them are favourable, it may be possible to breed to simultaneously improve the plantation resource for both products. Acoustic wave velocity (AWV) measured in standing trees can predict wood stiffness, basic density, and kraft pulp yield (KPY) and therefore has the potential for use in tree breeding programs. From an E. nitens progeny trial in Tasmania, 540 trees were selected for rotary peeling. Of the wood properties assessed, there were significant differences among races in diameter, stem straightness, standing-tree, log, and billet AWV, and near infrared predicted cellulose content (CC). All traits displayed significant within-race genetic variation, and genetic correlations between AWV and veneer sheet mo...
Summary Two Tasmanian provenance trials of Eucalyptus globulus Labili, and related species of blu... more Summary Two Tasmanian provenance trials of Eucalyptus globulus Labili, and related species of blue gum—E pseudoglobulus Naudin ex Maiden, E. bicostata Maid, et al., and E. maidenii F. Muell.—were analysed for growth, form and survival differences between species and between provenances within species. E globulus and E pseudoglobulus were not significantly different in growth but both were much faster growing than E bicostata and E maidenii which appeared to be poorly adapted to the cool temperate climate of Tasmania. Cross sites analysis did not identify significant consistent variation between provenances within species for height at age 4 years or diameter at age 7 years. Provenance differences were significant when sites were analysed separately although there was little differentiation within E globulus for growth characters. Significant differences were found in survival and form score between species and provenances within species. Implications for future work within this group of species are discussed.
The future of forests in Asia and the Pacific: …, 2009
... Forest Management (SFM), which were enunciated in The Forest Principles, adopted at the Unite... more ... Forest Management (SFM), which were enunciated in The Forest Principles, adopted at the UnitedNations Conference on Environment and ... At the International Conference on EngagingCommunities, the Brisbane Declaration on Community Engagement (2005) outlined ...
Genetic-parameter estimates and parental breeding-value predictions were compared from open-polli... more Genetic-parameter estimates and parental breeding-value predictions were compared from open-pollinated and control-pollinated progeny populations of Eucalyptus globulus and two populations of E. nitens. For E. globulus there were two types of open-pollinated populations (native stand open-pollinated and seed orchard open-pollinated) and two types of control-pollinated populations (intra-provenance and interprovenance full-sib families). For E. nitens there were two populations, a seed orchard open-pollinated population and intra-provenance full-sib families. Progeny tests were established across multiple sites and 2-year height and diameter were measured and volume calculated. Genetic parameters from native stand open-pollinated E. globulus were unlike the parameters from the other three E. globulus populations; heritability estimates were severely inflated, presumably due to high levels, and possibly differential levels, of inbreeding depression relative to the other populations. Estimates of dominance variance in the E. globulus full-sib populations were high, but were zero in the E. nitens population. Correlations among parental breeding values, predicted using data from the different populations, were generally low and non-significant, with two exceptions: predictions from the two E. globulus full-sib populations were significantly correlated (r=0.54, P = 0.001), as were predictions from the E. nitens seed orchard OP and full-sib population (r = 0.61, P = 0.08). There was some indication that superior parents of E. globulus native stand open-pollinated families also tended to have above-average breeding values based on the performance of intra-provenance full-sib offspring. The consequences of these results for exploitation of base-population collections from native stands are discussed.
AGRIS record. Record number, SK1998000651. Titles, Provenance variation, genotype by environment ... more AGRIS record. Record number, SK1998000651. Titles, Provenance variation, genotype by environment interactions and age - age correlations for Eucalyptus regnans on nine sites in south-eastern Australia. Personal Authors, ...
Intra-specific hybrids within Eucalyptus nitens and E. globulus were compared directly with inter... more Intra-specific hybrids within Eucalyptus nitens and E. globulus were compared directly with inter-specific E. nitens × globulus using common parents. Diameter (age 2, 4, 6, 10 years) and Pilodyn (age 6 years) were used as indirect measures of growth and wood density, respectively. Genetic parameters were estimated for all cross types and traits. A direct comparison of the general combining ability with the general hybridising ability was made. Heterosis was estimated for intra- and inter-specific hybrids. The intra-specific hybrids in both species exhibit intermediate heritabilities and levels of additive genetic variance. The inter-specific F1 E. nitens × globulus exhibited high incidence of abnormalities at young ages and high levels of later age mortality. The mean performance of surviving inter-specific F1 hybrids was generally intermediate for all traits, to varying degrees, between the parental intra-specific crosses, and there is little evidence for significant heterosis. Different provenances of E. globulus may exhibit different responses to hybridisation. In this case, the inter-specific F1 hybrids, using Taranna E. globulus, appear to perform worse on average than those using King Island provenance for growth traits. There is evidence that specific hybrid families are produced that outperform most of the pure species families for one or other of the traits examined; however, there is no reliable quantitative genetic method of predicting which parents should be used.
The use of hybrid eucalypts in commercial forestry has generally resulted from opportunistic cros... more The use of hybrid eucalypts in commercial forestry has generally resulted from opportunistic crossing events with superior individuals being vegetatively propagated in large numbers. To develop strategies to breed hybrids, it is important to understand the barriers to hybridisation in the genus and as well as the genetic behavior of hybrid populations. Using F 1 hybrid populations of E. gunnii × globulus, E. nitens × globulus and outcrossed parental controls we demonstrate, firstly, the importance of environment on hybrid performance and secondly, that high levels of F 1 and advanced generation hybrid inviability can occur at an early age, even in crosses between closely related species. Inviable F 1 hybrids are a sensitive indicator of genomic incompatibility and add a cost to hybrid selection and production. However, surviving F 1 's may be vigorous and of interest to breeders. F 1 hybrid populations do not appear to conform to classical quantitative genetic models for growth with inflated estimates of additive genetic variance and poor predictability of hybrid performance. Nevertheless, this does not appear to be so for other more highly heritable traits. Advanced generation hybridisation is one means of overcoming the constraints and costs of poor clonal propagation and F 1 hybrid seed production, but hybrid breakdown may substantially reduce genetic gains.
Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to ... more Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to supplement native forest ‘ash ’ eucalypt logs for the Tasmanian sawmilling industry. Processing methods developed for native forest euca-
The first Europeans to discover Eucalyptus globulus were French explorers in 1792. Its seed was r... more The first Europeans to discover Eucalyptus globulus were French explorers in 1792. Its seed was rapidly spread throughout the world in the 19th century and this was the species by which much of the world first knew the genus. However, it was in the industrial forests of the 20th century that this species, once considered the ‘Prince of Eucalypts’, achieved greatest prominence due to its fast growth and superior pulp qualities. Formal breeding first commenced in 1966 in Portugal and in the late 1980’s large base population trials from open-pollinated seed collections from native stands were established in many countries. These trials have provided
Effective nutrition management is vital for optimising productivity in many eucalypt plantations,... more Effective nutrition management is vital for optimising productivity in many eucalypt plantations, to protect the large investment in pruning for solid wood production and meet long-term woodflow targets. A fertiliser decision support tool, EucFERT, has been developed which is helping forest managers to maximise growth responses while being economic and minimising off-site nutrient losses. The tool uses detailed local soil information along with crop and site data to provide guidance on a stand basis. Predicted growth responses to fertiliser are based on long-term nutrition experiments covering early-rotation and mid-rotation trials across a range of site and soil types. Outputs from EucFERT can be used to prepare Stand fertiliser management plans that include soil and site management, fertiliser product, rate, application, frequency and timing, along with environmental and operational cautions relating to aerial application. The use of this computerised tool provides much greater co...
Forty-nine provenances from a rangewide collection of Eucalyptus regnans F. Muell were establishe... more Forty-nine provenances from a rangewide collection of Eucalyptus regnans F. Muell were established at each of 12 sites throughout its natural distribution. Trees on the nine surviving sites were assessed for diameter at breast height, stem straightness and branching quality at ages between 9 and 13 years. Provenance differences were found at each site but genotype by environment interactions were also significant. Provenance rankings differed between sites and no single provenance or group of provenances was found to be among the best for all traits at all sites. Several provenances (Mt Useful, Quarry Creek. Buchan, Otway Messmate and New I-Iaven) were consistently amongst the worst for growth at all sites. For stem straightness Narbethong was outstanding, ranking highly across all sites, whereas Lavers Hill, Christmas Hills and Strathblane were consistently amongst the worst. Local provenances did not perform amongst the best at eight out of the nine sites. Provenances collected fr...
Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protec... more Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protección de los bosques naturales. Como resultado, los productores de maderas de alto valor han dirigido su interés a las plantaciones de Eucalyptus como una fuente para el suministro de madera de latifoliadas que tradicionalmente se obtenía de bosques naturales. Varias especies de Eucalyptus se han establecido
Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to ... more Thinned and pruned plantation-grown Eucalyptus nitens (H.Deane & Maiden) Maiden has potential to supplement native forest 'ash' eucalypt logs for the Tasmanian sawmilling industry. Processing methods developed for native forest euca-lypts were applied to logs from 22-year-old pruned stands thinned at age six years to 100, 200, 300, 400 stems/ha and unthinned control stands with a stocking of 700 stems/ha at harvest. Consistent with existing industry requirements for the two sawing methods, 42 trees with diameter at breast height over bark (DBHOB) < 43 cm were selected for back-sawing (fl at-sawing), and 39 trees with DBHOB > 43 cm for quarter-sawing. For each sawing method, sets of trees were selected to provide trees evenly distributed across the target diameter range and, as near as possible, with sets matched across thinning treatments for size. From each tree two sawlogs, nominally 2.7 m in length, were cut from the pruned part of the stem. Both logs from individua...
Primeros resultados de un ensayo de severidad de poda en Eucalyptus regnans: efectos 1 en el crec... more Primeros resultados de un ensayo de severidad de poda en Eucalyptus regnans: efectos 1 en el crecimiento y respuesta fisiológica. 2 Peter 3 4 5 6 7 RESUMEN 8 Las crecientes preocupaciones de los consumidores en materias ambientales han llevado a la protección 9 de los bosques naturales. Como resultado, los productores de maderas de alto valor han dirigido su 10 interés a las plantaciones de Eucalyptus como una fuente para el suministro de madera de latifoliadas 11 que tradicionalmente se obtenía de bosques naturales. Varias especies de Eucalyptus se han establecido 12 en diversos países desde los trópicos hasta las zonas de clima templado frío. Una especie de interés en 13 la zona fría y templada, es E. regnans, que se ha establecido con éxito en Nueva Zelanda y Chile. En su 14 medio natural, los bosques esclerófilos húmedos del sureste de Australia, puede alcanzar alturas 15 cercanas a 100 metros y es una de las maderas más populares para una amplia gama de productos, 16 incluidos ...
Effective nutrition management is vital for optimising productivity in many eucalypt plantations,... more Effective nutrition management is vital for optimising productivity in many eucalypt plantations, to protect the large investment in pruning for solid wood production and meet long-term woodflow targets. A fertiliser decision support tool, EucFERT, has been developed which is helping forest managers to maximise growth responses while being economic and minimising off-site nutrient losses. The tool uses detailed local soil information along with crop and site data to provide guidance on a stand basis. Predicted growth responses to fertiliser are based on long-term nutrition experiments covering early-rotation and mid-rotation trials across a range of site and soil types. Outputs from EucFERT can be used to prepare Stand fertiliser management plans that include soil and site management, fertiliser product, rate, application, frequency and timing, along with environmental and operational cautions relating to aerial application. The use of this computerised tool provides much greater co...
The photosynthetic response to pruning was measured in two Eucalyptus regnans stands, aged 2 and ... more The photosynthetic response to pruning was measured in two Eucalyptus regnans stands, aged 2 and 3 years, located in areas of high productivity on the coast of the province of Arauco, Chile. Variables such as rates of CO 2 assimilation and stomatal conductance were measured in three ages of foliage on trees with different pruning severity treatments, which corresponded to the removal of 0 % (control), 30, 50 and 70 % of live crown length. The 2-year-old stand measurements were performed at the time of pruning and 6, 10, 14 and 18 weeks later, and the 3-year stand, 5, 9, 18 and 28 weeks after pruning. In both trials, significant differences were found between the foliage ages for all instances of measurement showing the mature foliage the highest values up to 30 % higher than old foliage. There were also significant differences between pruning severity treatments in both trials in which, in general, the highest values of CO 2 assimilation were observed among the highest pruning severity treatments with values up to 40 % higher than the unpruned trees.
... thinning operations open the canopy to wind penetration and can dramatically increase the vul... more ... thinning operations open the canopy to wind penetration and can dramatically increase the vulnerability of a stand to windthrow (Savill, 1983; Ruel, 1995; Quine ... The incidence of windthrow has been positively related to the rate of thinning (Ruth and Yoder, 1953; Booth, 1974). ...
Genetic improvement of wood properties affecting the quality of pulpwood and peeled veneer produc... more Genetic improvement of wood properties affecting the quality of pulpwood and peeled veneer products is of general interest to tree breeders worldwide. If the wood properties of Eucalyptus nitens (H. Deane & Maiden) Maiden are under genetic control and the correlations between them are favourable, it may be possible to breed to simultaneously improve the plantation resource for both products. Acoustic wave velocity (AWV) measured in standing trees can predict wood stiffness, basic density, and kraft pulp yield (KPY) and therefore has the potential for use in tree breeding programs. From an E. nitens progeny trial in Tasmania, 540 trees were selected for rotary peeling. Of the wood properties assessed, there were significant differences among races in diameter, stem straightness, standing-tree, log, and billet AWV, and near infrared predicted cellulose content (CC). All traits displayed significant within-race genetic variation, and genetic correlations between AWV and veneer sheet mo...
Summary Two Tasmanian provenance trials of Eucalyptus globulus Labili, and related species of blu... more Summary Two Tasmanian provenance trials of Eucalyptus globulus Labili, and related species of blue gum—E pseudoglobulus Naudin ex Maiden, E. bicostata Maid, et al., and E. maidenii F. Muell.—were analysed for growth, form and survival differences between species and between provenances within species. E globulus and E pseudoglobulus were not significantly different in growth but both were much faster growing than E bicostata and E maidenii which appeared to be poorly adapted to the cool temperate climate of Tasmania. Cross sites analysis did not identify significant consistent variation between provenances within species for height at age 4 years or diameter at age 7 years. Provenance differences were significant when sites were analysed separately although there was little differentiation within E globulus for growth characters. Significant differences were found in survival and form score between species and provenances within species. Implications for future work within this group of species are discussed.
The future of forests in Asia and the Pacific: …, 2009
... Forest Management (SFM), which were enunciated in The Forest Principles, adopted at the Unite... more ... Forest Management (SFM), which were enunciated in The Forest Principles, adopted at the UnitedNations Conference on Environment and ... At the International Conference on EngagingCommunities, the Brisbane Declaration on Community Engagement (2005) outlined ...
Genetic-parameter estimates and parental breeding-value predictions were compared from open-polli... more Genetic-parameter estimates and parental breeding-value predictions were compared from open-pollinated and control-pollinated progeny populations of Eucalyptus globulus and two populations of E. nitens. For E. globulus there were two types of open-pollinated populations (native stand open-pollinated and seed orchard open-pollinated) and two types of control-pollinated populations (intra-provenance and interprovenance full-sib families). For E. nitens there were two populations, a seed orchard open-pollinated population and intra-provenance full-sib families. Progeny tests were established across multiple sites and 2-year height and diameter were measured and volume calculated. Genetic parameters from native stand open-pollinated E. globulus were unlike the parameters from the other three E. globulus populations; heritability estimates were severely inflated, presumably due to high levels, and possibly differential levels, of inbreeding depression relative to the other populations. Estimates of dominance variance in the E. globulus full-sib populations were high, but were zero in the E. nitens population. Correlations among parental breeding values, predicted using data from the different populations, were generally low and non-significant, with two exceptions: predictions from the two E. globulus full-sib populations were significantly correlated (r=0.54, P = 0.001), as were predictions from the E. nitens seed orchard OP and full-sib population (r = 0.61, P = 0.08). There was some indication that superior parents of E. globulus native stand open-pollinated families also tended to have above-average breeding values based on the performance of intra-provenance full-sib offspring. The consequences of these results for exploitation of base-population collections from native stands are discussed.
AGRIS record. Record number, SK1998000651. Titles, Provenance variation, genotype by environment ... more AGRIS record. Record number, SK1998000651. Titles, Provenance variation, genotype by environment interactions and age - age correlations for Eucalyptus regnans on nine sites in south-eastern Australia. Personal Authors, ...
Intra-specific hybrids within Eucalyptus nitens and E. globulus were compared directly with inter... more Intra-specific hybrids within Eucalyptus nitens and E. globulus were compared directly with inter-specific E. nitens × globulus using common parents. Diameter (age 2, 4, 6, 10 years) and Pilodyn (age 6 years) were used as indirect measures of growth and wood density, respectively. Genetic parameters were estimated for all cross types and traits. A direct comparison of the general combining ability with the general hybridising ability was made. Heterosis was estimated for intra- and inter-specific hybrids. The intra-specific hybrids in both species exhibit intermediate heritabilities and levels of additive genetic variance. The inter-specific F1 E. nitens × globulus exhibited high incidence of abnormalities at young ages and high levels of later age mortality. The mean performance of surviving inter-specific F1 hybrids was generally intermediate for all traits, to varying degrees, between the parental intra-specific crosses, and there is little evidence for significant heterosis. Different provenances of E. globulus may exhibit different responses to hybridisation. In this case, the inter-specific F1 hybrids, using Taranna E. globulus, appear to perform worse on average than those using King Island provenance for growth traits. There is evidence that specific hybrid families are produced that outperform most of the pure species families for one or other of the traits examined; however, there is no reliable quantitative genetic method of predicting which parents should be used.
The use of hybrid eucalypts in commercial forestry has generally resulted from opportunistic cros... more The use of hybrid eucalypts in commercial forestry has generally resulted from opportunistic crossing events with superior individuals being vegetatively propagated in large numbers. To develop strategies to breed hybrids, it is important to understand the barriers to hybridisation in the genus and as well as the genetic behavior of hybrid populations. Using F 1 hybrid populations of E. gunnii × globulus, E. nitens × globulus and outcrossed parental controls we demonstrate, firstly, the importance of environment on hybrid performance and secondly, that high levels of F 1 and advanced generation hybrid inviability can occur at an early age, even in crosses between closely related species. Inviable F 1 hybrids are a sensitive indicator of genomic incompatibility and add a cost to hybrid selection and production. However, surviving F 1 's may be vigorous and of interest to breeders. F 1 hybrid populations do not appear to conform to classical quantitative genetic models for growth with inflated estimates of additive genetic variance and poor predictability of hybrid performance. Nevertheless, this does not appear to be so for other more highly heritable traits. Advanced generation hybridisation is one means of overcoming the constraints and costs of poor clonal propagation and F 1 hybrid seed production, but hybrid breakdown may substantially reduce genetic gains.
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