Comparison of CEPA (2-chloroethyl phosphonic acid) induced responses in juvenile Eucalyptus nitens, E. globulus and E. obliqua: A histochemical and anatomical study

Kino veins and/or pockets are a characteristic defect of some Eucalyptus species and have long been recognized as sources of degrade in eucalypt timber. In a comparative study, the course of both histochemical and anatomical responses of three juvenile Eucalyptus species (E. nitens, E. globulus and E. obliqua) to treatment with an ethylene-releasing compound, 2-chloroethyl phosphonic acid (CEPA), were examined. Kino veins were induced in both E. obliqua and E. globulus. The hormone treatment failed to induce kino vein formation in E. nitens. The traumatic parenchyma (that later differentiated into kino veins) was not always derived from the initials of the vascular cambium as reported in previous studies of E. globulus. Instead, the traumatic parenchyma appeared to be produced from the meristematic activity of the inner phloem parenchyma. In addition, kino veins found in 2- to 3-year-old E. globulus were mostly included in the phloem and not in the xylem as generally observed in mature E. globulus

Identification of hydrolysable tannins in the reaction zone of Eucalyptus nitens wood by high performance liquid chromatrography-electrospray ionisation mass spectrometry

The first detailed analysis of the phenolic constituents of the reaction zones (tissue of antimicrobial defence) from the sapwood of a Eucalyptus spp. is presented. Plantation-grown Eucalyptus nitens trees with stem decay resulting from pruning wounds were sampled and extracts were prepared from healthy sapwood and from reaction zone tissue. Analysis by HPLC with ESI-MS revealed that a diverse range of hydrolysable tannins are present in both healthy sapwood and in reaction zone extracts, including over 30 gallotannins, ellagitannins and phenols. Eight tannins were unequivocally identified, including the gallotannins tri-O-galloyl-β-D-glucose, tetra-O-galloyl-β-D-glucose and penta-O-galloyl-β-D-glucose, and the ellagitannins pedunculagin, tellimagrandin I, casuarinin, casuarictin and tellimagrandin II. The phenols gallic acid, ellagic acid and catechin were also identified. The ellagitannins (particularly pedunculagin) are considerably more abundant in the reaction zone than in the healthy sapwood and may contribute to the effectiveness of the reaction zone as an antimicrobial barrier

Crown-scale evaluation of spectral indices for defoliated and discoloured eucalypts

Remote sensing for evaluation of canopy health in plantation eucalypts is a realistic option for forest managers in the near future if reliable and robust methods of spectral analysis can be developed. Pot-grown eucalypts of three species important to the Australian plantation industry were used for crown-scale spectral (400–1000 nm) evaluations of vegetation indices as indicators of common symptoms of stress. When defoliation treatments (in E. globulus) or exposure to cold and nutrient deprivation (in E. pilularis) resulted in large differences in leaf cover, the red edge position and slope indices, two normalized difference vegetation indices (NDVIs), modified chlorophyll absorption ratio index 2 (MCARI2) or modified triangular vegetation index 2 (MTVI2) were most strongly correlated to leaf cover. However the NDVIs were significantly affected by soil background in a study with E. globulus. The percentage of red leaves resulting from stress treatment was most strongly correlated with the anthocyanin reflectance index (ARI) and red-green index (RGI) in both E. grandis and E. pilularis, however the RGI was affected by background type in the E. globulus study while the ARI was not. Exposure to cold and nutrient deprivation led to marked changes in leaf cover for E. pilularis but not in E. grandis and a much more reduced level of chlorophyll in E. pilularis than is suspected in E. grandis. In E. globulus, defoliation from the upper crown was easier to detect with spectral data than from the lower crown. Results were generally comparable to studies of eucalypt crown condition from native forests

Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations of Tasmania, Australia

The genus Mycosphaerella Johanson contains many pathogens capable of causing a severe impact on the growth of susceptible eucalypt species. The lack of knowledge about which species are present in Tasmania and their potential risk to the plantation industry prompted this study into the Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations in Tasmania. A total of 36 plantation and ®ve road verge sites of E. globulus and E. nitens were sampled. Five Mycosphaerella species and three species from associated anamorph genera were isolated and identi®ed in Tasmania; Mycosphaerella nubilosa, Mycosphaerella cryptica, Mycosphaerella tasmaniensis, Mycosphaerella grandis, Mycosphaerella vespa, Coniothyrium ovatum, Sonderhenia eucalypticola and Sonderhenia eucalyptorum. The most frequently isolated species with the highest incidence and severity of infection were M. cryptica and M. nubilosa. These two species appear to have the greatest potential to damage juvenile eucalypt plantations in Tasmania. A link between Mycosphaerella vespa and Coniothyrium ovatum is described for the ®rst time

Ease of access to an alternative food source enables wallabies to strip bark in Tasmanian Pinus radiata plantations

Bark stripping by the Bennett’s wallaby (Macropus rufogriseus (Desmarest) subsp. rufogriseus) from the lower stems of 3–6-year-old radiata pine (Pinus radiata D. Don) causes significant damage in Tasmanian plantations. The usual diet of this generalist herbivore is mainly grasses and broadleaved forbs. As the factors that attract a wallaby to supplement its diet by eating the bark of plantation pine trees are currently not elucidated, the present study aimed to determine how the incidence and severity of bark damage in 12 Tasmanian radiata pine plantations was influenced by various inter-site factors such as the floristic composition of the surrounding forest, and by various intra-site factors such as the height and circumference of individual trees, the number of branches in the first two whorls at the base of the tree, and their internode lengths. It was found that the greater the percentages of bare ground, bracken, and moss present in the five plots at each site, and the greater the percentage of grass, the wallaby’s main food source, the greater the likelihood of bark stripping. The difference between the mean minimum soil and air temperatures in spring, a driving force for carbohydrate production that occurs with tree growth in spring or early summer, was the only meteorological observation at the sites that was found to be significantly related to the extent of bark stripping

Polyphenols in Acacia mangium and Acacia auriculiformis heartwood with reference to heart rot susceptibility

The heartwood of Acacia mangium is vulnerable to heart rot and this is the first study to investigate the role of heartwood extractives in its susceptibility. Acacia auriculiformis was compared with A. mangium because it is rarely associated with heart rot. The heartwood extracts of both species were dominated by three flavonoids (2,3-trans-3,4′,7,8-tetrahydroxyflavanone, teracacidin, and 4′,7,8,-trihydroxyflavanone), which were purified and identified by nuclear magnetic resonance spectroscopy. The latter compound has not been previously reported in A. mangium and evidence for melacacidin is also newly reported. The mass spectrometric (MS) behavior of these compounds is given, for example teracacidin does not form molecular ions by either electrospray ionization or atmospheric-pressure chemical ionization. The nature of Acacia tannins was compared to quebracho tannin (composed of profisetinidins) using oxidative cleavage to enable MS detection but a negative reaction was obtained for both, which suggests the Acacia tannins may also be of the 5-deoxy proanthocyanidin type. The concentration of flavanones was less when A. mangium heartwood was decayed but the amount of proanthocyanidins was only slightly reduced and therefore these compounds may be more resistant to degradation by heart rot fungi. We found that the total phenol content of A. auriculiformis was about fivefold that of A. mangium, and, while preliminary, this provides evidence for a role played by phenolic extractives in heart rot resistance of these Acacia species

Interdisciplinary approach to the study and management of stem defect in eucalypts

In Australia large areas of forest have been closed to industrial forestry and it is necessary to compensate for lost production. Future wood products will come from intensively managed silvicultural regimes — eucalypt regrowth forest and plantations. Solid-wood regimes involving high-cost operations such as pruning and thinning will be economically sensitive to downgrade due to various types of stem defect — fungal and insect damage, staining, kino veins. In Tasmania, research over the last decade has focused on developing management strategies to minimise stem defect caused by decay fungi in both regrowth and plantation eucalypts. Under plantation conditions neither Eucalyptus nitens (Deane & Maiden) Maiden nor E. globulus Labill. shed branches efficiently. Retention of dead branches leads to defects in wood such as a large knotty core or loose knots, making the stem unsuitable for either veneer or sawlog. Pruning of green branches at canopy closure and in subsequent lifts shortly afterwards solves this problem. However, on the more productive warm and wet sites there is a high level of decay infections in E. nitens and E. globulus via pruning wounds. We are investigating the complex pathological, physiological, genetic, and silvicultural components dictating eucalypt susceptibility to decay infection and its long-term spread into clearwood including: crown characteristics prior to pruning; growth responses to pruning; growth responses to fertiliser; host resistance and antimicrobial defences; and the identity and pathogenicity of decay fungi. An interdisciplinary approach is fundamental to understanding such questions and also to the successful development of site productivity models that include predictions of risk and impact of biotic and abiotic damage

Quantitative genetic control of mycosphaerella resistance in Eucalyptus globulus and impact on growth

Fungi of the genus Mycosphaerella is one of the major leaf disease of Eucalyptus globulus worldwide. The main species that infect E. globulus in southern Australia are M. cryptica and M. nubilosa. M. nubilosa is mainly confined to the juvenile foliage whereas M. cryptica may occur on both foliage types. Mycosphaerella damage to E. globulus plantations can be severe and the risk of disease damage is one of the main reasons for the shift towards planting the more resistant E. nitens in northern Tasmania. We examined the quantitative genetic variation in susceptibility to infection by M. nubilosa in a genetically diverse population of E. globulus families growing in a field trial in north-west Tasmania. The trees were two years old and still entirely in the juvenile foliage stage when a heavy epidemic of M. nubilosa occurred. Disease incidence was uniform across the trial and the mean leaf area damage (severity assessed as % of necrotic of lost leaves on whole tree basis) was very high at 34%. Significant genetic variation for susceptibility was detected with a narrow-sense heritability of disease severity of 0.6 being the highest yet reported for a Mycosphaerella disease of eucalypts. We followed the effects of this disease outbreak on growth up to age 7 years and found that M. nubilosa damage had a significantly deleterious impact on tree growth at both the phenotypic and genetic level. At age 7, the top 10% of families had a mean DBH 20.8% greater than the trial mean. Approximately half of this gain would have been achieved by early selection for disease resistance (9.1%) or height (11.0%) at age 2, with a time advantage of 5 years. This is similarly the case for selection of above average families. It is likely such gains would be reduced in homogenous plantings of resistant genotypes, or if genotype x environment interactions are significant. Nevertheless, a large component of this gain is likely to be due to disease resistance per se, and collection of seed from resistant seed orchard parents offers the potential for rapid gains in productivity in plantations at risk of diseaseAbstract Fungi of the genus Mycosphaerella is one of the major leaf disease of Eucalyptus globulus worldwide. The main species that infect E. globulus in southern Australia are M. cryptica and M. nubilosa. M. nubilosa is mainly confined to the juvenile foliage whereas M. cryptica may occur on both foliage types. Mycosphaerella damage to E. globulus plantations can be severe and the risk of disease damage is one of the main reasons for the shift towards planting the more resistant E. nitens in northern Tasmania. We examined the quantitative genetic variation in susceptibility to infection by M. nubilosa in a genetically diverse population of E. globulus families growing in a field trial in north-west Tasmania. The trees were two years old and still entirely in the juvenile foliage stage when a heavy epidemic of M. nubilosa occurred. Disease incidence was uniform across the trial and the mean leaf area damage (severity assessed as % of necrotic of lost leaves on whole tree basis) was very high at 34%. Significant genetic variation for susceptibility was detected with a narrow-sense heritability of disease severity of 0.6 being the highest yet reported for a Mycosphaerella disease of eucalypts. We followed the effects of this disease outbreak on growth up to age 7 years and found that M. nubilosa damage had a significantly deleterious impact on tree growth at both the phenotypic and genetic level. At age 7, the top 10% of families had a mean DBH 20.8% greater than the trial mean. Approximately half of this gain would have been achieved by early selection for disease resistance (9.1%) or height (11.0%) at age 2, with a time advantage of 5 years. This is similarly the case for selection of above average families. It is likely such gains would be reduced in homogenous plantings of resistant genotypes, or if genotype x environment interactions are significant. Nevertheless, a large component of this gain is likely to be due to disease resistance per se, and collection of seed from resistant seed orchard parents offers the potential for rapid gains in productivity in plantations at risk of diseaseAbstract Fungi of the genus Mycosphaerella is one of the major leaf disease of Eucalyptus globulus worldwide. The main species that infect E. globulus in southern Australia are M. cryptica and M. nubilosa. M. nubilosa is mainly confined to the juvenile foliage whereas M. cryptica may occur on both foliage types. Mycosphaerella damage to E. globulus plantations can be severe and the risk of disease damage is one of the main reasons for the shift towards planting the more resistant E. nitens in northern Tasmania. We examined the quantitative genetic variation in susceptibility to infection by M. nubilosa in a genetically diverse population of E. globulus families growing in a field trial in north-west Tasmania. The trees were two years old and still entirely in the juvenile foliage stage when a heavy epidemic of M. nubilosa occurred. Disease incidence was uniform across the trial and the mean leaf area damage (severity assessed as % of necrotic of lost leaves on whole tree basis) was very high at 34%. Significant genetic variation for susceptibility was detected with a narrow-sense heritability of disease severity of 0.6 being the highest yet reported for a Mycosphaerella disease of eucalypts. We followed the effects of this disease outbreak on growth up to age 7 years and found that M. nubilosa damage had a significantly deleterious impact on tree growth at both the phenotypic and genetic level. At age 7, the top 10% of families had a mean DBH 20.8% greater than the trial mean. Approximately half of this gain would have been achieved by early selection for disease resistance (9.1%) or height (11.0%) at age 2, with a time advantage of 5 years. This is similarly the case for selection of above average families. It is likely such gains would be reduced in homogenous plantings of resistant genotypes, or if genotype x environment interactions are significant. Nevertheless, a large component of this gain is likely to be due to disease resistance per se, and collection of seed from resistant seed orchard parents offers the potential for rapid gains in productivity in plantations at risk of diseas

Incidence of heartrot in harvest-age Acacia mangium in Indonesia, using a rapid survey method

The potential to use plantation-grown Acacia mangium for solid-timber products is limited by heartrot, caused by decay fungi. A rapid method of surveying logs stacked in the plantation following harvest was developed which is an alternative to time-consuming whole tree destructive assessments. Logs were randomly chosen from the stacks using a transect method, the cut-ends of the logs were assessed (2199 logs in total) and heartrot severity was scored on a 1–4 scale. Surveys of harvest-age A. mangium were completed in five Indonesian locations to assess heartrot incidence and severity. The incidence of heartrot in the main stem was significantly different between some regions, ranging from 6.7% in East Kalimantan up to 46.7% in West Java. The proportion of each defect type (1–4) did not show a consistent trend across the sites. A combination of differences between plantation management (e.g. pruning), age and climate in these five regions explain the differences in heartrot incidence and severity

Mycosphaerella leaf diseases of temperate eucalypts around the Southern Pacific rim

Research with Mycosphaerella spp. on eucalypts has been historically and strongly focused towards taxonomical species descriptions, extension of host, and geographical range. To date there is insufficient information to develop management prescriptions that can be applied operationally. The research concept we have adopted is an integration of empirical studies (detection, impact, epidemiology, and physiology) and designed experiments that provide a knowledge base from which models can be developed and validated. Our empirical studies and designed experiments form a core response to current industry priorities in Australia