Background and Aims Stomatal conductance has long been considered of key interest in the study of... more Background and Aims Stomatal conductance has long been considered of key interest in the study of plant adaptation to water stress. The expected increase in extreme meteorological events under a climate change scenario may compromise survival in Eucalyptus globulus plantations established in southwestern Spain. We investigated to what extent changes in stomatal conductance in response to high vapour pressure deficits and water shortage are mediated by hydraulic and chemical signals in greenhouse-grown E. globulus clones. Methods Rooted cuttings were grown in pots and submitted to two watering regimes. Stomatal conductance, shoot water potential, sap pH and hydraulic conductance were measured consecutively in each plant over 4 weeks under vapour pressure deficits ranging 0Á42 to 2Á25 kPa. Evapotranspiration, growth in leaf area and shoot biomass were also determined. Key Results There was a significant effect of both clone and watering regime in stomatal conductance and leaf-specific hydraulic conductance, but not in sap pH. Sap pH decreased as water potential and stomatal conduc-tance decreased under increasing vapour pressure deficit. There was no significant relationship between stomatal conductance and leaf-specific hydraulic conductance. Stomata closure precluded shoot water potential from falling below À1Á8 MPa. The percentage loss of hydraulic conductance ranged from 40 to 85 %. The highest and lowest leaf-specific hydraulic conductances were measured in clones from the same half-sib families. Water shortage reduced growth and evapotranspiration, decreases in evapotranspiration ranging from 14 to 32 % in the five clones tested. Conclusions Changes in sap pH seemed to be a response to changes in atmospheric conditions rather than soil water in the species. Stomata closed after a considerable amount of hydraulic conductance was lost, although intraspecific differences in leaf-specific hydraulic conductance suggest the possibility of selection for improved productivity under water-limiting conditions combined with high temperatures in the early stages of growth.
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 19 th 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 20 th 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 unprecedented insights into the quantitative genetic control of numerous traits of economic and ecological importance and how this variation is spatially distributed in the native range of the species. However with large, fully pedigreed breeding populations becoming available for quantitative analysis and the rapidly expanding knowledge of DNA sequence variation, we are now at the threshold of a new understanding of this important eucalypt gene pool. Indications of the significance of non-additive genetic effects are becoming available. The E. globulus chloroplast genome has now been sequenced and several genome maps have been published. Studies of the variation in nuclear microsatellites and the lignin biosynthesis gene CCR confirm the complex, spatially structured nature of the native gene pool. Strong spatial structuring of the chloroplast genome has provided a tool for tracking seed migration and the geographic origin of exotic landraces. Highly divergent lineages of chloroplast DNA have been discovered and studies of the hypervariable J LA+ region argue that some components of the E. globulus gene pool have been assimilated from other species following hybridisation.
Using native trees from near the northern and southern extremities of the relatively continuous e... more Using native trees from near the northern and southern extremities of the relatively continuous eastern distribution of Eucalyptus globulus in Tasmania, we compared the progenies derived from natural open-pollination (OP) with those generated from within-region and long-distance outcrossing. Controlled outcrossing amongst eight parents - with four parents from each of the northern and southern regions - was undertaken using a diallel mating scheme. The progeny were planted in two field trials located within the species native range in southern Tasmania, and their survival and diameter growth were monitored over a 13-year-period. The survival and growth performances of all controlled cross types exceeded those of the OP progenies, consistent with inbreeding depression due to a combination of selfing and bi-parental inbreeding. The poorer survival of the northern regional (♀N♂N) outcrosses compared with the local southern regional outcrosses (♀S♂S) indicated differential selection against the former. Despite this mal-adaptation of the non-local ♀N♂N crosses at both southern sites, the survival of the inter-regional hybrids (♀N♂S and ♀S♂N) was never significantly different from that of the local ♀S♂S crosses. Significant site-dependent heterosis was detected for the growth of the surviving long-distance hybrids. This was expressed as mid-parent heterosis, particularly at the more northern planting site. Heterosis increased with age, while the difference between the regional ♀N♂N and ♀S♂S crosses remained insignificant at any age at either site. Nevertheless, the results for growth suggest that the fitness of individuals derived from long-distance crossing may be better at the more northern of the planting sites. Our results demonstrate the potential for early-age assessments of pollen dispersal to underestimate realised gene flow, with local inbreeding under natural open-pollination resulting in selection favouring the products of longer-distance pollinations. Indeed, heterosis derived from long-distance pollinations may be sufficient to counter local mal-adaptation, at least in the first generation.
Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these pl... more Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 • C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality. field performance / frost tolerance / mineral nutrients / non-structural carbohydrates / root egress Résumé -La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d'Eucalyptus globulus Labill. Eucalyptus globulus est largement utilisé dans des plantations exotiques productives, mais l'expansion de ces plantations est limitée par les basses températures, étant donné que l'endurcissement potentiel au froid de cette espèce est limité (0,5 à 3,0 • C). On ne comprenait pas bien comment la fertilisation en pépinière pouvait affecter la performance en plantation des plants. Ceci nous a amené à étudier l'effet de trois nutriments minéraux (N, P et K) sur la qualité des plants et la résistance au froid. L'expérimentation a comporté huit traitements pour l'étude de la croissance pour lesquels une forte dose (H-) ou une faible dose (L-) de chaque nutriment a été apportée. L'azote a été le nutriment qui a déterminé la croissance de la pousse, la croissance de nouvelles racines après transplantation (émission de racines), la résistance au froid et la performance en plantation. Les performances étaient meilleures avec le traitement H-N que avec le traitement L-N, la teneur en azote des feuilles atteignant respectivement 1,53 et 0,89 %. Les effets du phosphore et du potassium n'ont été significatifs pour aucun des paramètres. L'exception a concerné le phosphore qui lorsqu'il était en interaction avec l'azote a favorisé l'émission de racines dans le traitement H-N. On conclut de cette étude que la fertilisation en pépinière offre un outil de gestion pour les producteurs d'eucalyptus confrontés au problème de la qualité des plants.
Genetic parameters for diameter and Pilodyn penetration at 3 and 4 years of age were estimated fr... more Genetic parameters for diameter and Pilodyn penetration at 3 and 4 years of age were estimated from trials of a Eucalyptus globulus base population established at four sites in Buenos Aires Province, Argentina. The trials comprised open-pollinated families from native stands and land race selections from different countries. A posteriori blocking was applied to improve the fitting of the mixed model and then multivariate analyses were undertaken with ASREML to estimate within race (co-)variance components. Breeding values of parents and offspring were predicted using Best Linear Unbiased Prediction with an individual tree model. Heritabilities were moderate for diameter (0.12 -0.35) and higher for pilodyn penetration (0.43 -0.52). The across site genetic correlation for diameter was high, ranging from 0.85 to 1.0, and was 0.81 between the two sites where pilodyn penetration was measured. Correlations between diameter and pilodyn penetration were effectively zero. The implications of these results for the development of a deployment population are discussed.
There is increasing interest in using Eucalyptus maidenii as an alternative to E. globulus for pu... more There is increasing interest in using Eucalyptus maidenii as an alternative to E. globulus for pulpwood plantations in the warmer, central-northern regions of Argentina. Preliminary plantations established in this area for saw log production were successful and stimulated further exploration of this species. Four trials were established by INTA between 1995 and 1997, two close to the E. globulus planting zone and the other two, 400 and 1000km further north. The trials included 108-150 families from 11 native provenances from New South Wales, Australia and one comprising open pollinated seed collected from phenotypic selections from a local plantation in Cortines, Argentina, of unknown origin. Diameter at age 4 and 5 years old was evaluated and family least square means calculated for each site. These means were used in a mixed model analysis examining the effects of site, provenance and their interaction as fixed effects and family within provenance as a random effect. There was no significant effect of provenance, but the provenance by site (P<0.05) and family within provenance (P<0.001) effects were significant. The large difference between sites (P<0.001) partly reflected better growth at the two northern sites. The best growth was observed at the site 400km north of the E. globulus planting zone. The local selections from Cortines were generally the best performing on all sites. The best performing native stand provenance was from Dobbyns Road.
For early field growth, Eucalyptus ovata x globulus F 1 hybrids were as vigorous as outcross, ope... more For early field growth, Eucalyptus ovata x globulus F 1 hybrids were as vigorous as outcross, open-pollinated, and selfed progeny of both pure species. However, after 10 years few hybrids were alive compared to the pure species. These results emphasise the hazard of judging hybrid performance from early growth. The cross types were grown in separate sub-blocks to avoid competition, yet even then the total basal area of the F 1 hybrids after 10 years growth was 78% less than the outcrossed mid-parent value. This compares with inbreeding depression due to selfing of 48 and 79% in E. globulus and E. ovata, respectively. The actual diameter of F 1 hybrids, which did survive, was not significantly different from the parental controls. However, in later years, individual tree growth rates would be biased due to different competitive environments arising from genetically based mortality.
In most F 1 hybrids of Eucalyptus, flowering time was intermediate or synchronous with either par... more In most F 1 hybrids of Eucalyptus, flowering time was intermediate or synchronous with either parent. One exception was E. ovata x globulus. While the pure species were synchronous in their flowering, the flowering of the F 1 hybrids was delayed with virtually no overlap with the parental species. This delay is a consequence of the additive inheritance of the timing of flower bud development. E. globulus takes one year between bud initiation and flowering whereas E. ovata requires two years.
The planting method is one of the factors that affect most plant performance in the field. This s... more The planting method is one of the factors that affect most plant performance in the field. This study analyses and describes the results obtained in two trials of deep-planting with a clonal stock of Eucalyptus globulus.
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 19 th 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 20 th 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 unprecedented insights into the quantitative genetic control of numerous traits of economic and ecological importance and how this variation is spatially distributed in the native range of the species. However with large, fully pedigreed breeding populations becoming available for quantitative analysis and the rapidly expanding knowledge of DNA sequence variation, we are now at the threshold of a new understanding of this important eucalypt gene pool. Indications of the significance of non-additive genetic effects are becoming available. The E. globulus chloroplast genome has now been sequenced and several genome maps have been published. Studies of the variation in nuclear microsatellites and the lignin biosynthesis gene CCR confirm the complex, spatially structured nature of the native gene pool. Strong spatial structuring of the chloroplast genome has provided a tool for tracking seed migration and the geographic origin of exotic landraces. Highly divergent lineages of chloroplast DNA have been discovered and studies of the hypervariable J LA+ region argue that some components of the E. globulus gene pool have been assimilated from other species following hybridisation.
Clonal forestry is the best way for deploying the genetic gains but the low rooting success in fo... more Clonal forestry is the best way for deploying the genetic gains but the low rooting success in forestry species is sometimes a limitation for breeding. Eucalyptus globulus is one of the most difficult species to root in the genus. There are previous studies of E. globulus genetic variation on many traits but not on the rooting trait. This study examines samples from the full range of geographic variation and report genetic parameters. Subraces showed differences in performance for rooting and narrow sense heritability was moderate (h 2 = 0.23).
Maternal and nonmaternal reciprocal effects were compared with nuclear genetic and carryover effe... more Maternal and nonmaternal reciprocal effects were compared with nuclear genetic and carryover effects using a diallel mating amongst eight Eucalyptus globulus Labill. wild parents from northeastern and southern Tasmania races. Seed mass exhibited a significant maternal effect, increasing seed germinative capacity but not germination rate. After accounting for variation in seed mass, both germinative capacity and germination rate exhibited significant reciprocal effects, but these were nonmaternal in origin. Rapid germination and large seeds resulted in significantly larger seedlings in the nursery, but these carryover effects diminished with age. In contrast, the expression of genetic effects increased with age. Significant additive genetic variation was detected for growth by age 3 years and significant reciprocal differences were detected at the race level after 2 years in field trials. If common, such reciprocal effects could bias genetic parameters and impact on the choice of cross-direction in deployment programs. Failure to account for carryover effects in genetic analyses may inflate estimates of genetic variation for growth during early stages of the life cycle. Résumé : Les auteurs ont comparé les effets réciproques maternels et non maternels aux effets génétiques nucléaires et de transfert à l'aide d'un plan de croisement diallèle impliquant huit parents à l'état sauvage d'Eucalyptus globulus Labill. représentatifs des races du Nord-Est et du Sud de la Tasmanie. La masse des graines a démontré un effet maternel significatif, augmentant la capacité germinative mais pas le taux de germination. Après avoir tenu compte de l'effet de la masse des graines, la capacité germinative ainsi que le taux de germination ont démontré des effets réciproques significatifs sans être d'origine maternelle. Un taux de germination rapide et de grosses graines donnaient des semis significativement plus gros en pépinière, mais ces effets de transfert diminuaient avec l'âge. Au contraire, l'expression des effets génétiques augmentait avec l'âge. Une variation génétique d'origine additive significative a été détectée pour la croissance à l'âge de 3 ans et des différences réciproques significatives ont été détectées au niveau des races dans les dispositifs au champ après 2 ans. Si ces effets réciproques sont courants, ils pourraient biaiser les paramètres génétiques et influencer le choix du sens des croisements lors de la réalisation des programmes de déploiement. La négligence des effets de transfert lors des analyses génétiques peut entraîner des estimations trop élevées de la variation génétique pour la croissance durant les stades juvéniles du cycle de vie.
The dispersion of the genus Eucalyptus in nature is by seeds. Nevertheless, the interest from bre... more The dispersion of the genus Eucalyptus in nature is by seeds. Nevertheless, the interest from breeders to reproduce outstanding trees by cuttings encourages the development and adjustment of techniques for agamic propagation. These techniques may be classified as in vitro and in vivo, according to the environment in which they take place. While in vivo stem cutting are widely employed in Eucalyptus mass propagation, in vitro techniques are standing by for their use. Cuttings play an important role in tree improvement because they capture desirable genes without recombination as occurs in seed production. The access to clonal culture enhances the possibility of hybrids. Eucalypus hybrids have the attractiveness of combining two features in a single individual, each one contributed by one of the parental species. Explorative inter-specific control crosses have been largely undertaken and some combinations of tropical species come up as core genetic material in plantation at commercial scale. In particular, E. globulus was acknowledged a recalcitrant species for rooting but in early 1990´s, ENCE changed this qualification and started using vegetative mass propagation of clones in operational plantations. The techniques for rooting cuttings were adjusted first for macro and then for mini-cuttings, thereby generating a production of 6 millions cuttings per year. Vegetative propagation is an accepted tool to achieve great gains in a short time. The deployment of selected clones by ENCE was successful because it almost duplicated pulp wood production yield at rotation age. In advance selection the criteria of wood properties was included. However, these traits are not the only feature of interest, also uniformity in plantation is a valuable advantage for management and wood logging. The clonal strategy needs a well-planned breeding program. Only the support of a broad breeding program guarantees sustainable gains by way of more productive new clones also for the establishment of new markets or identification of new invasive pest or diseases.
Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness an... more Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness and survival were estimated in a base-population of five open-pollinated provenance/progeny trials of Eucalyptus viminalis. The trials, located in northern, central and southern Buenos Aires Province, Argentina, comprised 148 open-pollinated families from 13 Australian native provenances and eight local Argentinean seedlots. The Australian native provenances come from a limited range of the natural distribution. Overall survival, based on the latest assessment of each trial, was 62.4%. Single-site analyses showed that statistically significant provenances differences (p<0.05) for at least one of the studied traits in three out of the five trials analyzed. The local land race performed inconsistently in this study. The average narrow-sense individual-tree heritability estimate b h 2 was 0.27 for diameter and 0.17 for total height. Values of b h 2 also increased with age. Pilodyn penetration, assessed at only one site, was more heritable b h 2 ¼ 0:32 than the average of growth traits. Estimated individual-tree heritabilities were moderate to low for stem straightness (average of 0.20) and relative bark thickness (0.16). The estimated additive genetic correlations r A ð Þ between diameter and height were consistently high and positive (rAaverage of 0.90). High additive genetic correlations were observed between growth variables and pilodyn penetration (rA average of 0.58). Relative bark thickness showed a negative correlation with diameter rA ¼ À0:39 ð Þ and height rA ¼ À0:51 ð Þ . The average estimated additive genetic correlation between sites was high for diameter (0.67). The implications of all these parameter estimates for genetic improvement of E. viminalis in Argentina are discussed.
With human intervention, wild forest species have gone from being exploited in the wild to being ... more With human intervention, wild forest species have gone from being exploited in the wild to being cultivated. This process of domestication on a species changes the composition of its genetic resources. In this review, Eucalyptus globulus is used to illustrate the process of domestication and describes the milestones that occur in tree farming. Knowledge of genetic variation and genetic parameters are the most useful tools in choosing the strategy of conservation and improvement. Adaptation to new environments causes changes in genetic and is a fundamental basis in most of the improvement program. Improvement strategies meet the guidelines and managements to reproduce genetic gain. This is achieved through the production of seeds in seed orchards, and clones selected for vegetative propagation at the operational level. The adjustment of the vegetative propagation technique has consolidated very wealthy genetic gains and allows extending its application in eucalypt hybrids. E. globulus is a reference species in domestication, cultivation, tree improvement and biotechnology developments.
The impact of inbreeding and hybridization on ®tness was compared in the two co-occurring forest ... more The impact of inbreeding and hybridization on ®tness was compared in the two co-occurring forest tree species, Eucalyptus ovata and E. globulus, aimed at explaining the rarity of their hybrids in nature. The success of sel®ng, open-pollination and outcrossing of both species and interspeci®c hybridization was monitored from seed-set to 10-year's growth in a ®eld trial. There was a unilateral barrier to hybridization with seed-set obtained only with E. ovata females. The F 1 hybrids exhibited reduced viability compared to intraspeci®c cross-types at virtually all stages of the life cycle and are clearly at a selective disadvantage compared with their open-pollinated E. ovata half-sibs with which they would directly compete in nature. Eucalyptus ovata and E. globulus overlap in their ¯owering time but the F 1 hybrids ¯owered later with virtually no overlap with either species. The asynchronous ¯owering and reduced reproductive ®tness of F 1 hybrids would markedly limit the opportunity for advanced generation hybridization. Inbreeding similarly had a deleterious eect on the ®tness of both species, and the F 1 hybrids were most competitive with the E. ovata selfs. It is argued that changes in inbreeding levels of parental populations may be a key factor aecting the relative ®tness of hybrids and their potential to impact on the pure species gene pool. Reduced ®tness of the pure species through inbreeding may result in hybridization having its greatest evolutionary impact in small founder or relict populations.
Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these pl... more Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 • C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality. field performance / frost tolerance / mineral nutrients / non-structural carbohydrates / root egress Résumé -La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d'Eucalyptus globulus Labill. Eucalyptus globulus est largement utilisé dans des plantations exotiques productives, mais l'expansion de ces plantations est limitée par les basses températures, étant donné que l'endurcissement potentiel au froid de cette espèce est limité (0,5 à 3,0 • C). On ne comprenait pas bien comment la fertilisation en pépinière pouvait affecter la performance en plantation des plants. Ceci nous a amené à étudier l'effet de trois nutriments minéraux (N, P et K) sur la qualité des plants et la résistance au froid. L'expérimentation a comporté huit traitements pour l'étude de la croissance pour lesquels une forte dose (H-) ou une faible dose (L-) de chaque nutriment a été apportée. L'azote a été le nutriment qui a déterminé la croissance de la pousse, la croissance de nouvelles racines après transplantation (émission de racines), la résistance au froid et la performance en plantation. Les performances étaient meilleures avec le traitement H-N que avec le traitement L-N, la teneur en azote des feuilles atteignant respectivement 1,53 et 0,89 %. Les effets du phosphore et du potassium n'ont été significatifs pour aucun des paramètres. L'exception a concerné le phosphore qui lorsqu'il était en interaction avec l'azote a favorisé l'émission de racines dans le traitement H-N. On conclut de cette étude que la fertilisation en pépinière offre un outil de gestion pour les producteurs d'eucalyptus confrontés au problème de la qualité des plants.
Background and Aims Stomatal conductance has long been considered of key interest in the study of... more Background and Aims Stomatal conductance has long been considered of key interest in the study of plant adaptation to water stress. The expected increase in extreme meteorological events under a climate change scenario may compromise survival in Eucalyptus globulus plantations established in southwestern Spain. We investigated to what extent changes in stomatal conductance in response to high vapour pressure deficits and water shortage are mediated by hydraulic and chemical signals in greenhouse-grown E. globulus clones. Methods Rooted cuttings were grown in pots and submitted to two watering regimes. Stomatal conductance, shoot water potential, sap pH and hydraulic conductance were measured consecutively in each plant over 4 weeks under vapour pressure deficits ranging 0Á42 to 2Á25 kPa. Evapotranspiration, growth in leaf area and shoot biomass were also determined. Key Results There was a significant effect of both clone and watering regime in stomatal conductance and leaf-specific hydraulic conductance, but not in sap pH. Sap pH decreased as water potential and stomatal conduc-tance decreased under increasing vapour pressure deficit. There was no significant relationship between stomatal conductance and leaf-specific hydraulic conductance. Stomata closure precluded shoot water potential from falling below À1Á8 MPa. The percentage loss of hydraulic conductance ranged from 40 to 85 %. The highest and lowest leaf-specific hydraulic conductances were measured in clones from the same half-sib families. Water shortage reduced growth and evapotranspiration, decreases in evapotranspiration ranging from 14 to 32 % in the five clones tested. Conclusions Changes in sap pH seemed to be a response to changes in atmospheric conditions rather than soil water in the species. Stomata closed after a considerable amount of hydraulic conductance was lost, although intraspecific differences in leaf-specific hydraulic conductance suggest the possibility of selection for improved productivity under water-limiting conditions combined with high temperatures in the early stages of growth.
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 19 th 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 20 th 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 unprecedented insights into the quantitative genetic control of numerous traits of economic and ecological importance and how this variation is spatially distributed in the native range of the species. However with large, fully pedigreed breeding populations becoming available for quantitative analysis and the rapidly expanding knowledge of DNA sequence variation, we are now at the threshold of a new understanding of this important eucalypt gene pool. Indications of the significance of non-additive genetic effects are becoming available. The E. globulus chloroplast genome has now been sequenced and several genome maps have been published. Studies of the variation in nuclear microsatellites and the lignin biosynthesis gene CCR confirm the complex, spatially structured nature of the native gene pool. Strong spatial structuring of the chloroplast genome has provided a tool for tracking seed migration and the geographic origin of exotic landraces. Highly divergent lineages of chloroplast DNA have been discovered and studies of the hypervariable J LA+ region argue that some components of the E. globulus gene pool have been assimilated from other species following hybridisation.
Using native trees from near the northern and southern extremities of the relatively continuous e... more Using native trees from near the northern and southern extremities of the relatively continuous eastern distribution of Eucalyptus globulus in Tasmania, we compared the progenies derived from natural open-pollination (OP) with those generated from within-region and long-distance outcrossing. Controlled outcrossing amongst eight parents - with four parents from each of the northern and southern regions - was undertaken using a diallel mating scheme. The progeny were planted in two field trials located within the species native range in southern Tasmania, and their survival and diameter growth were monitored over a 13-year-period. The survival and growth performances of all controlled cross types exceeded those of the OP progenies, consistent with inbreeding depression due to a combination of selfing and bi-parental inbreeding. The poorer survival of the northern regional (♀N♂N) outcrosses compared with the local southern regional outcrosses (♀S♂S) indicated differential selection against the former. Despite this mal-adaptation of the non-local ♀N♂N crosses at both southern sites, the survival of the inter-regional hybrids (♀N♂S and ♀S♂N) was never significantly different from that of the local ♀S♂S crosses. Significant site-dependent heterosis was detected for the growth of the surviving long-distance hybrids. This was expressed as mid-parent heterosis, particularly at the more northern planting site. Heterosis increased with age, while the difference between the regional ♀N♂N and ♀S♂S crosses remained insignificant at any age at either site. Nevertheless, the results for growth suggest that the fitness of individuals derived from long-distance crossing may be better at the more northern of the planting sites. Our results demonstrate the potential for early-age assessments of pollen dispersal to underestimate realised gene flow, with local inbreeding under natural open-pollination resulting in selection favouring the products of longer-distance pollinations. Indeed, heterosis derived from long-distance pollinations may be sufficient to counter local mal-adaptation, at least in the first generation.
Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these pl... more Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 • C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality. field performance / frost tolerance / mineral nutrients / non-structural carbohydrates / root egress Résumé -La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d'Eucalyptus globulus Labill. Eucalyptus globulus est largement utilisé dans des plantations exotiques productives, mais l'expansion de ces plantations est limitée par les basses températures, étant donné que l'endurcissement potentiel au froid de cette espèce est limité (0,5 à 3,0 • C). On ne comprenait pas bien comment la fertilisation en pépinière pouvait affecter la performance en plantation des plants. Ceci nous a amené à étudier l'effet de trois nutriments minéraux (N, P et K) sur la qualité des plants et la résistance au froid. L'expérimentation a comporté huit traitements pour l'étude de la croissance pour lesquels une forte dose (H-) ou une faible dose (L-) de chaque nutriment a été apportée. L'azote a été le nutriment qui a déterminé la croissance de la pousse, la croissance de nouvelles racines après transplantation (émission de racines), la résistance au froid et la performance en plantation. Les performances étaient meilleures avec le traitement H-N que avec le traitement L-N, la teneur en azote des feuilles atteignant respectivement 1,53 et 0,89 %. Les effets du phosphore et du potassium n'ont été significatifs pour aucun des paramètres. L'exception a concerné le phosphore qui lorsqu'il était en interaction avec l'azote a favorisé l'émission de racines dans le traitement H-N. On conclut de cette étude que la fertilisation en pépinière offre un outil de gestion pour les producteurs d'eucalyptus confrontés au problème de la qualité des plants.
Genetic parameters for diameter and Pilodyn penetration at 3 and 4 years of age were estimated fr... more Genetic parameters for diameter and Pilodyn penetration at 3 and 4 years of age were estimated from trials of a Eucalyptus globulus base population established at four sites in Buenos Aires Province, Argentina. The trials comprised open-pollinated families from native stands and land race selections from different countries. A posteriori blocking was applied to improve the fitting of the mixed model and then multivariate analyses were undertaken with ASREML to estimate within race (co-)variance components. Breeding values of parents and offspring were predicted using Best Linear Unbiased Prediction with an individual tree model. Heritabilities were moderate for diameter (0.12 -0.35) and higher for pilodyn penetration (0.43 -0.52). The across site genetic correlation for diameter was high, ranging from 0.85 to 1.0, and was 0.81 between the two sites where pilodyn penetration was measured. Correlations between diameter and pilodyn penetration were effectively zero. The implications of these results for the development of a deployment population are discussed.
There is increasing interest in using Eucalyptus maidenii as an alternative to E. globulus for pu... more There is increasing interest in using Eucalyptus maidenii as an alternative to E. globulus for pulpwood plantations in the warmer, central-northern regions of Argentina. Preliminary plantations established in this area for saw log production were successful and stimulated further exploration of this species. Four trials were established by INTA between 1995 and 1997, two close to the E. globulus planting zone and the other two, 400 and 1000km further north. The trials included 108-150 families from 11 native provenances from New South Wales, Australia and one comprising open pollinated seed collected from phenotypic selections from a local plantation in Cortines, Argentina, of unknown origin. Diameter at age 4 and 5 years old was evaluated and family least square means calculated for each site. These means were used in a mixed model analysis examining the effects of site, provenance and their interaction as fixed effects and family within provenance as a random effect. There was no significant effect of provenance, but the provenance by site (P<0.05) and family within provenance (P<0.001) effects were significant. The large difference between sites (P<0.001) partly reflected better growth at the two northern sites. The best growth was observed at the site 400km north of the E. globulus planting zone. The local selections from Cortines were generally the best performing on all sites. The best performing native stand provenance was from Dobbyns Road.
For early field growth, Eucalyptus ovata x globulus F 1 hybrids were as vigorous as outcross, ope... more For early field growth, Eucalyptus ovata x globulus F 1 hybrids were as vigorous as outcross, open-pollinated, and selfed progeny of both pure species. However, after 10 years few hybrids were alive compared to the pure species. These results emphasise the hazard of judging hybrid performance from early growth. The cross types were grown in separate sub-blocks to avoid competition, yet even then the total basal area of the F 1 hybrids after 10 years growth was 78% less than the outcrossed mid-parent value. This compares with inbreeding depression due to selfing of 48 and 79% in E. globulus and E. ovata, respectively. The actual diameter of F 1 hybrids, which did survive, was not significantly different from the parental controls. However, in later years, individual tree growth rates would be biased due to different competitive environments arising from genetically based mortality.
In most F 1 hybrids of Eucalyptus, flowering time was intermediate or synchronous with either par... more In most F 1 hybrids of Eucalyptus, flowering time was intermediate or synchronous with either parent. One exception was E. ovata x globulus. While the pure species were synchronous in their flowering, the flowering of the F 1 hybrids was delayed with virtually no overlap with the parental species. This delay is a consequence of the additive inheritance of the timing of flower bud development. E. globulus takes one year between bud initiation and flowering whereas E. ovata requires two years.
The planting method is one of the factors that affect most plant performance in the field. This s... more The planting method is one of the factors that affect most plant performance in the field. This study analyses and describes the results obtained in two trials of deep-planting with a clonal stock of Eucalyptus globulus.
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 19 th 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 20 th 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 unprecedented insights into the quantitative genetic control of numerous traits of economic and ecological importance and how this variation is spatially distributed in the native range of the species. However with large, fully pedigreed breeding populations becoming available for quantitative analysis and the rapidly expanding knowledge of DNA sequence variation, we are now at the threshold of a new understanding of this important eucalypt gene pool. Indications of the significance of non-additive genetic effects are becoming available. The E. globulus chloroplast genome has now been sequenced and several genome maps have been published. Studies of the variation in nuclear microsatellites and the lignin biosynthesis gene CCR confirm the complex, spatially structured nature of the native gene pool. Strong spatial structuring of the chloroplast genome has provided a tool for tracking seed migration and the geographic origin of exotic landraces. Highly divergent lineages of chloroplast DNA have been discovered and studies of the hypervariable J LA+ region argue that some components of the E. globulus gene pool have been assimilated from other species following hybridisation.
Clonal forestry is the best way for deploying the genetic gains but the low rooting success in fo... more Clonal forestry is the best way for deploying the genetic gains but the low rooting success in forestry species is sometimes a limitation for breeding. Eucalyptus globulus is one of the most difficult species to root in the genus. There are previous studies of E. globulus genetic variation on many traits but not on the rooting trait. This study examines samples from the full range of geographic variation and report genetic parameters. Subraces showed differences in performance for rooting and narrow sense heritability was moderate (h 2 = 0.23).
Maternal and nonmaternal reciprocal effects were compared with nuclear genetic and carryover effe... more Maternal and nonmaternal reciprocal effects were compared with nuclear genetic and carryover effects using a diallel mating amongst eight Eucalyptus globulus Labill. wild parents from northeastern and southern Tasmania races. Seed mass exhibited a significant maternal effect, increasing seed germinative capacity but not germination rate. After accounting for variation in seed mass, both germinative capacity and germination rate exhibited significant reciprocal effects, but these were nonmaternal in origin. Rapid germination and large seeds resulted in significantly larger seedlings in the nursery, but these carryover effects diminished with age. In contrast, the expression of genetic effects increased with age. Significant additive genetic variation was detected for growth by age 3 years and significant reciprocal differences were detected at the race level after 2 years in field trials. If common, such reciprocal effects could bias genetic parameters and impact on the choice of cross-direction in deployment programs. Failure to account for carryover effects in genetic analyses may inflate estimates of genetic variation for growth during early stages of the life cycle. Résumé : Les auteurs ont comparé les effets réciproques maternels et non maternels aux effets génétiques nucléaires et de transfert à l'aide d'un plan de croisement diallèle impliquant huit parents à l'état sauvage d'Eucalyptus globulus Labill. représentatifs des races du Nord-Est et du Sud de la Tasmanie. La masse des graines a démontré un effet maternel significatif, augmentant la capacité germinative mais pas le taux de germination. Après avoir tenu compte de l'effet de la masse des graines, la capacité germinative ainsi que le taux de germination ont démontré des effets réciproques significatifs sans être d'origine maternelle. Un taux de germination rapide et de grosses graines donnaient des semis significativement plus gros en pépinière, mais ces effets de transfert diminuaient avec l'âge. Au contraire, l'expression des effets génétiques augmentait avec l'âge. Une variation génétique d'origine additive significative a été détectée pour la croissance à l'âge de 3 ans et des différences réciproques significatives ont été détectées au niveau des races dans les dispositifs au champ après 2 ans. Si ces effets réciproques sont courants, ils pourraient biaiser les paramètres génétiques et influencer le choix du sens des croisements lors de la réalisation des programmes de déploiement. La négligence des effets de transfert lors des analyses génétiques peut entraîner des estimations trop élevées de la variation génétique pour la croissance durant les stades juvéniles du cycle de vie.
The dispersion of the genus Eucalyptus in nature is by seeds. Nevertheless, the interest from bre... more The dispersion of the genus Eucalyptus in nature is by seeds. Nevertheless, the interest from breeders to reproduce outstanding trees by cuttings encourages the development and adjustment of techniques for agamic propagation. These techniques may be classified as in vitro and in vivo, according to the environment in which they take place. While in vivo stem cutting are widely employed in Eucalyptus mass propagation, in vitro techniques are standing by for their use. Cuttings play an important role in tree improvement because they capture desirable genes without recombination as occurs in seed production. The access to clonal culture enhances the possibility of hybrids. Eucalypus hybrids have the attractiveness of combining two features in a single individual, each one contributed by one of the parental species. Explorative inter-specific control crosses have been largely undertaken and some combinations of tropical species come up as core genetic material in plantation at commercial scale. In particular, E. globulus was acknowledged a recalcitrant species for rooting but in early 1990´s, ENCE changed this qualification and started using vegetative mass propagation of clones in operational plantations. The techniques for rooting cuttings were adjusted first for macro and then for mini-cuttings, thereby generating a production of 6 millions cuttings per year. Vegetative propagation is an accepted tool to achieve great gains in a short time. The deployment of selected clones by ENCE was successful because it almost duplicated pulp wood production yield at rotation age. In advance selection the criteria of wood properties was included. However, these traits are not the only feature of interest, also uniformity in plantation is a valuable advantage for management and wood logging. The clonal strategy needs a well-planned breeding program. Only the support of a broad breeding program guarantees sustainable gains by way of more productive new clones also for the establishment of new markets or identification of new invasive pest or diseases.
Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness an... more Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness and survival were estimated in a base-population of five open-pollinated provenance/progeny trials of Eucalyptus viminalis. The trials, located in northern, central and southern Buenos Aires Province, Argentina, comprised 148 open-pollinated families from 13 Australian native provenances and eight local Argentinean seedlots. The Australian native provenances come from a limited range of the natural distribution. Overall survival, based on the latest assessment of each trial, was 62.4%. Single-site analyses showed that statistically significant provenances differences (p<0.05) for at least one of the studied traits in three out of the five trials analyzed. The local land race performed inconsistently in this study. The average narrow-sense individual-tree heritability estimate b h 2 was 0.27 for diameter and 0.17 for total height. Values of b h 2 also increased with age. Pilodyn penetration, assessed at only one site, was more heritable b h 2 ¼ 0:32 than the average of growth traits. Estimated individual-tree heritabilities were moderate to low for stem straightness (average of 0.20) and relative bark thickness (0.16). The estimated additive genetic correlations r A ð Þ between diameter and height were consistently high and positive (rAaverage of 0.90). High additive genetic correlations were observed between growth variables and pilodyn penetration (rA average of 0.58). Relative bark thickness showed a negative correlation with diameter rA ¼ À0:39 ð Þ and height rA ¼ À0:51 ð Þ . The average estimated additive genetic correlation between sites was high for diameter (0.67). The implications of all these parameter estimates for genetic improvement of E. viminalis in Argentina are discussed.
With human intervention, wild forest species have gone from being exploited in the wild to being ... more With human intervention, wild forest species have gone from being exploited in the wild to being cultivated. This process of domestication on a species changes the composition of its genetic resources. In this review, Eucalyptus globulus is used to illustrate the process of domestication and describes the milestones that occur in tree farming. Knowledge of genetic variation and genetic parameters are the most useful tools in choosing the strategy of conservation and improvement. Adaptation to new environments causes changes in genetic and is a fundamental basis in most of the improvement program. Improvement strategies meet the guidelines and managements to reproduce genetic gain. This is achieved through the production of seeds in seed orchards, and clones selected for vegetative propagation at the operational level. The adjustment of the vegetative propagation technique has consolidated very wealthy genetic gains and allows extending its application in eucalypt hybrids. E. globulus is a reference species in domestication, cultivation, tree improvement and biotechnology developments.
The impact of inbreeding and hybridization on ®tness was compared in the two co-occurring forest ... more The impact of inbreeding and hybridization on ®tness was compared in the two co-occurring forest tree species, Eucalyptus ovata and E. globulus, aimed at explaining the rarity of their hybrids in nature. The success of sel®ng, open-pollination and outcrossing of both species and interspeci®c hybridization was monitored from seed-set to 10-year's growth in a ®eld trial. There was a unilateral barrier to hybridization with seed-set obtained only with E. ovata females. The F 1 hybrids exhibited reduced viability compared to intraspeci®c cross-types at virtually all stages of the life cycle and are clearly at a selective disadvantage compared with their open-pollinated E. ovata half-sibs with which they would directly compete in nature. Eucalyptus ovata and E. globulus overlap in their ¯owering time but the F 1 hybrids ¯owered later with virtually no overlap with either species. The asynchronous ¯owering and reduced reproductive ®tness of F 1 hybrids would markedly limit the opportunity for advanced generation hybridization. Inbreeding similarly had a deleterious eect on the ®tness of both species, and the F 1 hybrids were most competitive with the E. ovata selfs. It is argued that changes in inbreeding levels of parental populations may be a key factor aecting the relative ®tness of hybrids and their potential to impact on the pure species gene pool. Reduced ®tness of the pure species through inbreeding may result in hybridization having its greatest evolutionary impact in small founder or relict populations.
Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these pl... more Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 • C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality. field performance / frost tolerance / mineral nutrients / non-structural carbohydrates / root egress Résumé -La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d'Eucalyptus globulus Labill. Eucalyptus globulus est largement utilisé dans des plantations exotiques productives, mais l'expansion de ces plantations est limitée par les basses températures, étant donné que l'endurcissement potentiel au froid de cette espèce est limité (0,5 à 3,0 • C). On ne comprenait pas bien comment la fertilisation en pépinière pouvait affecter la performance en plantation des plants. Ceci nous a amené à étudier l'effet de trois nutriments minéraux (N, P et K) sur la qualité des plants et la résistance au froid. L'expérimentation a comporté huit traitements pour l'étude de la croissance pour lesquels une forte dose (H-) ou une faible dose (L-) de chaque nutriment a été apportée. L'azote a été le nutriment qui a déterminé la croissance de la pousse, la croissance de nouvelles racines après transplantation (émission de racines), la résistance au froid et la performance en plantation. Les performances étaient meilleures avec le traitement H-N que avec le traitement L-N, la teneur en azote des feuilles atteignant respectivement 1,53 et 0,89 %. Les effets du phosphore et du potassium n'ont été significatifs pour aucun des paramètres. L'exception a concerné le phosphore qui lorsqu'il était en interaction avec l'azote a favorisé l'émission de racines dans le traitement H-N. On conclut de cette étude que la fertilisation en pépinière offre un outil de gestion pour les producteurs d'eucalyptus confrontés au problème de la qualité des plants.
Ha pasado casi medio siglo. La que fuera Empresa Nacional de Celulosas, hoy ENCE, llegó a Huelva ... more Ha pasado casi medio siglo. La que fuera Empresa Nacional de Celulosas, hoy ENCE, llegó a Huelva como consecuencia de los trabajos ya desarrollados por Patrimonio Forestal del Estado con el género Eucalyptus en la provincia.
Según la naturaleza reproductiva de la especie, los árboles se han multiplicado principalmente po... more Según la naturaleza reproductiva de la especie, los árboles se han multiplicado principalmente por semillas o por reproducción vegetativa. Como excepción a las semillas pueden mencionarse otras alternativas menos frecuentes para la constitución de nuevas masas forestales, como lo son la regeneración por retoños o rebrotes. Sin embargo, con la contribución de los avances en mejora genética ha crecido el interés por controlar la producción de plantas, primero seleccionando, luego produciendo semillas y fi nalmente propagando vegetativamente a los individuos superiores.
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