Wind dispersal of Puccinia psidii urediniospores and progress of eucalypt rust

To identify and implement Puccinia psidii control strategies, it is essential to understand the role of environmental factors on rust‐disease development and spread among eucalypt (Eucalyptus spp.) plantations. In this study, we evaluated the wind dispersal of P. psidii urediniospores and the progress of eucalypt rust in a field trial in Brazil. Urediniospores of P. psidii were trapped in a Burkard^® spore trap from July 2004 to June 2005. To evaluate the progress of eucalypt rust, plots were established in March 2002 using a clonal hedge scheme. The incidence of both branches and leaves with rust was assessed weekly from February 2003 to October 2005. Disease progress was studied using time‐series analysis. Urediniospores were trapped on 77% of the days sampled. The highest average urediniospore concentration was detected from July to November, and most of the urediniospores (58%) were trapped at night. Urediniospore concentration was negatively correlated with rainfall, light intensity, minimum, average and maximum temperatures and wind speed, whereas urediniospore concentration was positively correlated with leaf‐wetness duration and relative humidity. From December 2004 to June 2005, average urediniospore concentration was 0.22 spores m^?3 air h^?1 and had no correlation with meteorological data. The highest average urediniospore concentration was associated with a combination of low average temperature, low light intensity, low wind speed, high relative humidity and high leaf wetness, which reflect conditions observed at night. The disease incidence was positively correlated with the urediniospores trapped at 12 days prior to disease assessment. According to the models obtained by the time series, a seasonal yearly effect was found on rust progress. Using our models, we were also able to forecast disease incidence up to 3 months after the last field assessment.     

An agglutination test for fast and specific detection of Erwinia psidii

Dieback and wilt, caused by Erwinia psidii (Ep), is one of the most important emergent diseases of Eucalyptus spp. in Brazil. Currently, pathogen detection relies on isolation of bacteria from infected plant tissue and either identification based on morphological, physiological and biochemical tests or DNA amplification using the polymerase chain reaction (PCR), which in many cases is laborious and cumbersome. Considering the need for a simpler and more rapid, yet reliable, method for detecting the pathogen, we obtained a polyclonal antibody (anti‐Ep) and developed an agglutination test for specific detection of E. psidii. The antiserum was produced against the E. psidii strain LPF534 and tested against 101 E. psidii isolates from Eucalyptus spp.; three E. psidii isolates from Psidium guajava; 23 Ralstonia solanacearum and 18 Xanthomonas axonopodis isolates pathogenic to Eucalyptus spp.; and seven endophytic isolates from Eucalyptus spp., three of which are phylogenetically related to the genus Erwinia. Results of direct ELISA indicated that a concentration as low as 3.5 µg/ml of the anti‐Ep antibody was able to detect the E. psidii antigen and that the antibody did not cross‐reacted with other bacteria pathogenic and non‐pathogenic to Eucalyptus spp. In the agglutination test, the anti‐Ep antibody showed positive reaction with all strains of E. psidii tested whereas cross‐reaction with none of the strains that belong to other taxonomic groups was observed. The agglutination test showed a detection limit of 10⁵ colony‐forming units (CFU)/ml, and its specificity was the same as that obtained by PCR amplification using E. psidii‐specific primers. These results demonstrate that the agglutination test developed here is a useful tool for specific, fast and inexpensive detection of E. psidii although only operational on pure bacterial suspensions and not yet directly from infected tissues.     

Wilt and die‐back of Eucalyptus spp. caused by Erwinia psidii in Brazil

A new disease of unknown bacterial aetiology has been observed in eucalyptus stands since 2009. It is characterized by die‐back, wilting and lesions on the branches, petiole and midrib in association with macroscopic and microscopic bacterial ooze. To date, this disease has been observed in stands of clonal Eucalyptus saligna, E. grandis and E. urophylla x E. grandis hybrids and in E. dunnii seedling plantations in the states of São Paulo, Rio Grande do Sul and Mato Grosso do Sul. Considering the economic importance of eucalyptus plantations and the potential losses caused by this disease, this study aimed to identify and characterize the causal agent. Thirty‐four strains were obtained from infected plants, which were collected in the field from four locations. The inoculation of detached leaves and intact rooted cuttings supported pathogenicity in eucalyptus. The phylogenetic analysis of four housekeeping genes (16S rDNA, gapA, recA and rpoB) as well as biochemical tests confirmed the identity of strains belonging to the species Erwinia psidii. This is the first report of E. psidii as the cause of wilt and die‐back in Eucalyptus spp. in Brazil.     

Increased atmospheric carbon dioxide concentration: effects on eucalypt rust (Puccinia psidii), C:N ratio and essential oils in eucalypt clonal plantlets

Evaluation of impacts of high CO₂ atmospheric concentration is strategically important for the development of adaptation measures and sustainable crop management. The objective of this study was to evaluate the effects of increased atmospheric CO₂ concentration on eucalypt rust (Puccinia psidii), C:N ratio, yield and chemical composition of essential oils and growth of eucalypt clonal plantlets. Two clones with different levels of rust resistance were studied: a Eucalyptus urophylla × E. camaldulensis hybrid (VM 01) and an E. urophylla (clone MN 463). The experiments were performed in open‐top chambers (OTCs) with CO₂ mean concentrations (μmol mol^?1) of 399 (unenclosed control), 412 (OTCs with ambient CO₂ concentration) and 508 (OTCs with high CO₂ concentration) and in closed chambers (CCs) with CO₂ mean concentrations of 390, 405, 520 and 700. Increased atmospheric CO₂ concentrations resulted in a decrease in rust pustules per leaf, uredinia per leaf area, spores per uredinia and area under the disease progress curve in VM 01 (hybrid) clonal plantlets. The disease did not occur in MN 463 clonal plantlets, which demonstrated that high CO₂ concentrations did not change the level of rust resistance. Plant growth of the two clones was stimulated by up to 23% in height and 26% in stem diameter in OTCs and by 18% for both clones in CCs. An increased C:N ratio in leaves, stems and roots was observed only for the VM 01 clonal plantlets. Essential oils produced by VM 01 (2.8 g 100 g^?1) and MN 463 (1.4 g 100 g^?1), as well as the major essential oil compounds (80% 1.8‐cineole for VM 01; 50% 1.8‐cineole and 32% α‐pinene for MN 463), were not altered. In this study, increased concentrations of atmospheric CO₂ favourably impacted eucalypt growth and reduced rust severity, while not influencing the production of essential oils.     

Host range of Erwinia psidii and genetic resistance of Eucalyptus and Corymbia species to this pathogen

Dieback caused by Erwinia psidii is currently one of the most important emerging diseases in eucalypt plantations in Brazil. However, little is known in terms of the host range of this pathogen or the potential sources of resistance against the disease it causes. In this study, we inoculated plants of species from nine families to gain insight into the host range of E. psidii. Plants of all inoculated species of Myrtaceae except Acca sellowiana exhibited disease symptoms and therefore represent potential hosts for the pathogen under natural conditions. In addition, the response of four Corymbia species, 29 Eucalyptus species and three interspecific Eucalyptus hybrids to inoculation with E. psidii was evaluated. All Corymbia henryi, Corymbia maculata, Eucalyptus thozetiana, Eucalyptus cloeziana, Eucalyptus viminalis, Eucalyptus dalrympleana and Eucalyptus pilularis plants were highly resistant to the pathogen, whereas differential disease resistance was observed in the other species. This study provides important information on sources of resistance to Erwinia psidii with potential use in the development of clones with enhanced resistance in eucalypt species of economic importance.     

观赏桉树及其在园林中的应用

对桃金娘科桉树属和伞房属中具有较高观赏价值的30多个种及品种的主要特点、天然分布以及在澳大利亚的栽培情况做了简要介绍。分析了观赏桉树在园林中的应用现状，展望其推广前景。对观赏桉树在我国园林中的推广应用具有参考价值。     

First report of Puccinia psidii on Corymbia citriodora and Eucalyptus in Colombia

A rust disease was observed during routine disease surveys of Eucalypt species in Colombia. The cause of the disease was identified, using morphology and DNA sequence data, as the myrtle rust pathogen, Puccinia psidii. We evaluated the susceptibility of Eucalyptus grandis and the hybrid Eucalyptus urograndis to P. psidii. This is the first report of this pathogen on Corymbia citriodora and Eucalyptus species in Colombia.     

桉树人工林与天然林土壤养分的对比研究

在野外调查取样和室内实验分析的基础上,对人工林与天然林的土壤养分进行比较分析,结果表明人工林土壤表层的有机质、全氮、全磷、全钾含量都明显低于天然林,反映了人工林对养分的旺盛需求和消耗,并且人工林还会造成土壤阳离子交换量的降低和土壤容重的增大。提出变炼山全垦为块状整地、轮栽并适当休闲养地、提高人工林生物多样性、建立复杂的人工林群落等措施,以实现桉树人工林土壤养分平衡与生态系统的良性循环。     

Impact of Austropuccinia psidii in New Caledonia,a biodiversity hotspot

Myrtle rust, caused by the fungus Austropuccinia psidii, infects a wide range of host species within the Myrtaceae family worldwide. Since its first report in 2013 from New Caledonia, the extent of the host range, geographical distribution and genetic diversity of A. psidii in this territory have been unknown. This study reports 67 new host species distributed in 13 different Myrtaceae genera, including five new genera. The pathogen was found in various types of plant communities, where Myrtaceae species are the dominant or codominant species, as well as in several nurseries. It is now considered a significant threat to the biodiversity of ecosystems and the Myrtaceae‐related economy. A 3‐year disease monitoring trial with 35 cultivated Myrtaceae species showed variations in disease severity at the species and individual scales. This suggests that some level of genetic resistance to myrtle rust may possibly exist among the endemic Myrtaceae of New Caledonia. A population genetic investigation revealed that only one single genotype of A. psidii occurs across its entire host range in New Caledonia. Therefore, it is essential to carry out population genetic surveillance to identify the appearance of mutations or the introduction of potentially more virulent genotypes of A. psidii. The outcomes from this study will assist with the ongoing management of the disease in New Caledonia.     

Realising the benefit of research in eucalypt plantation management

The development of a plantation eucalypt wood-based forest products industry in South Africa is outlined. Forest research that has contributed to increasing wood production from the ultimately finite land resource available for industrial plantations is reviewed. The application of this technology to eucalypt plantations by Sappi Forests is described and evidence for resultant increased wood production is presented. Improved silviculture, introduction of alternative species and deployment of genetically superior planting stock coupled to site classification and site-specific application of these technologies have all contributed to measured gains. The continued development and application of appropriate forest technology will be critical to a sustainable future for the industry in South Africa. Issues pertaining to this are discussed.     

惠安县桉树无性系引种试验

从人工杂交桉(尾叶桉×赤桉)TH9117和(尾叶桉×细叶桉)TH9211两家系营造的无性系试验林中选出最优的9个无性系与雷林1号桉的MJ41、刚果12号桉的2号、B号和W5等无性系,在1.5~3年生时对林分的树高、胸径、单株材积、单位面积蓄积量等生长指标进行比较分析。结果表明:杂交桉的LH6、LH4、LH5、LH1、LH7等5个无性系的4个生长指标均表现良好,其林木速生,胸径生长变异系数小,林相整齐,抗风与抗病性能好。尤其是LH4和LH6无性系,3年生时的单位面积蓄积量均达到154m3/hm2和152m3/hm2,比对照的W5无性系分别提高了2.02倍和1.98倍,且单株最大胸径达13.70cm,其增产效益较高。这5个优良无性系具有高产、优质、高效等特性,适合于营造短周期工业用材林,在生产上有很大的推广价值。     

Mineral cycling processes and system stability in the eucalypt forest

The effects of disturbance on the stability of the eucalypt forest are considered in terms of Bormann and Likens' (1979) schema of reorganisation, aggradation, transition and steady state phases of secondary succession.The difficulties of making reliable estimates of ecosystem nutrient reserves are discussed against a background of anisotropic nutrient distribution, inadequate knowledge of the volume of soil effectively exploited by roots, and the limitations of existing techniques for soil chemical analysis. The relative significance of the atmosphere and parent material for the accumulation of nutrient reserves is outlined and the overriding importance of the latter on soil phosphorus capital in the eucalypt forest is emphasised.The capacity of forest ecosystems to restrict changes in the ionic concentration of percolating soil water is indicated and some important facets of nutrient dynamics are described. Spatial and temporal patterns of substrate availability and microbial activity greatly complicate the measurement of organic matter decomposition and nutrient flux on the forest floor. Adaptations of eucalypts potentially significant in mineral cycling are mentioned.The role of natural agents of disturbance as determinants of pattern in plant communities is indicated, and the effects of man-induced disturbances such as clearcutting, burning of logging debris, and hazard reduction burning are discussed in the context of biogeochemical cycling. The importance of close operational control of management practices is stressed, together with the need for appropriate measures of functional stability.     

Repellent and stocking guards reduce mammal browsing in eucalypt plantations

Mammalian herbivores regularly browse plantation seedlings. In many areas, seedlings require some form of protection if they are to survive and grow into a productive plantation. Two general approaches for reducing browsing damage to seedlings are to apply chemical repellents and tree guards. Both methods have existed for a long time, and new variations are constantly being developed. Seedling stocking guards, a type of tree guard, are being used operationally in Tasmania, Australia, but there is limited data quantifying their effectiveness and concerns with negative effects on tree performance. Conversely, although proven effective, repellents are not being used, but are potentially cheaper and less problematic. We therefore aimed to determine which is more effective under operational conditions, whether this effectiveness can be improved or extended, and if either treatment has any effects on seedling form or survival. We planted Eucalyptus nitens seedlings with combinations of repellent and stocking guards in six operational plantations to examine and compare their effectiveness. Seedlings were monitored for 12 months to examine treatment longevity. We found that both stocking guards and repellent significantly reduced and delayed browsing severity, with their effects being additive. No negative effects on growth were evident after 12 months, but adverse effects on seedling form warrant further investigation. Both of these methods can be easily and relatively cheaply applied in the nursery before planting, making them appealing options to reduce browsing. However, the ideal method for a given site will depend upon local browsing intensity.     

Heart splitting at crosscutting of eucalypt logs

The occurrence of heart splitting during the crosscutting of logs was discussed in relation to the released strain on Eucalyptus spp. logs. The strains released in the longitudinal and tangential directions were measured by the strain-gauge method and were correlated with the length of the heart split measured on the same logs. There were differences in the longitudinal strain; however, no significant correlation was found with the diameter that could be converted to a mean annual increment (i.e., a relation with the growth rate). The initial splits expand with the time after felling. The longer the initial split, the longer is the length 1 week after felling. The split length was significantly smaller at the butt end of the first log of every tree than at the other end, but there were no significant differences between the split length at the top of the first logs and at either end of the second logs, although there were differences among individual trees. The length of the heart split correlated with the released strain near the pith, which was estimated using Kublers equation. The longitudinal released strain measured on the surface of logs is a good indicator of the heart splitting when crosscutting logs.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society     

The risk to Myrtaceae of Austropuccinia psidii,myrtle rust,in Mexico

Austropuccinia psidii is a biotrophic rust fungus that affects species from the Myrtaceae family. In Mexico, Myrtaceae is widely distributed in temperate, tropical and semi‐arid ecosystems, and includes 20 genera and 192 endemic and exotic species. Austropuccinia psidii has been present in Mexico for the last four decades; however, little is known about the distribution of this rust or the vulnerability of native and exotic Myrtaceae to infection. In this study, we used global occurrence records for the pandemic biotype of myrtle rust to model its current and future suitable habitat using a species distribution model, Maxent. We identified regions that are highly suitable for myrtle rust establishment, now and in the future (2050). Additionally, we identified the Myrtaceae species known to be susceptible to rust infection and that are currently distributed in areas with high rust habitat suitability. Thirty‐six susceptible plant species and 142 untested species are distributed within areas of suitable rust habitat and are considered potentially at risk of rust infection. Current suitable habitat is mainly restricted to the east coast of Mexico, with Veracruz, Puebla, Chiapas, Tabasco and Oaxaca being the most vulnerable regions to the rust under current and future climates. We encourage monitoring within these regions by surveying locations where the rust occurs and within areas with high suitable habitat to determine the threat to native ecosystems and industries reliant on Myrtaceae. We also recommend screening to test the susceptibility of Myrtaceae species with no known susceptibility rating.     

杨树肿茎溃疡病的测报及防治

对杨树肿茎溃疡病的发病情况，发生量测报技术，防治方法进行了调查研究，结果表明，杨树生长的立地条件，林分类型，林龄的大小民受害程度有直接关系，发生量测报技术，研究出各类型拟合方程和拟合理论值；根据试验和方差分析，最好的防治方法是应用“三威洗衣粉液”和“辣椒制剂”进行涂抹。     

Methods for inoculum production and inoculation of Cistella japonica,the causal agent of resinous stem canker in Chamaecyparis obtusa

The ascomycete Cistella japonica was cultured on potato dextrose agar medium (PDA) for inoculation into Chamaecyparis obtusa, enabling the development of an inoculation method suitable for use in a breeding programme aimed at selecting for families of Ch. obtusa resistant to resinous stem canker. Using PDA to generate the inoculum resolved the problems encountered with the previously used mixed medium of rice bran and wheat bran, including unfavourable characteristics, uncertain growth of Ci. japonica mycelia, and a complex culturing operation. The inoculation test induced resin exudation similar to that observed in natural infections, and reproduced clonal differences with regard to damage severity.     

Transpiration and hydraulic traits of old and regrowth eucalypt forest in southwestern Australia

We tested the hypothesis that overstorey of eucalypt forest dominated by tall, large diameter trees uses less water than regrowth stands in the high rainfall zone (>1100 mm year⁻¹) of the northern jarrah (Eucalyptus marginata) forest in southwestern Australia. We measured leaf area, cover, sapwood area and sapwood density at three paired old and regrowth stands. We also measured sapflow velocity at one paired stand (Dwellingup) from June 2007 to October 2008. Old stands had more basal area but less foliage cover, less leaf area and slightly thinner sapwood. The ratio of sapwood area to basal area decreased markedly as tree size increased. Sapwood area of the regrowth forest stands (6.6 ± 0.30 m² ha⁻¹) was nearly double that of the old stands (3.4 ± 0.17 m² ha⁻¹), despite larger basal area at the old stands. Leaf area index of the regrowth stands (2.1 ± 0.26) was only one-third larger than that at the old stands (1.5 ± 0.15); hence, the ratio of leaf area to sapwood area was larger in old stands than in regrowth stands (0.45 ± 0.022 m² cm⁻² versus 0.32 ± 0.045 m² cm⁻²). Our results are consistent with theories that trees have evolved to optimize carbon gain rather than maintain stomatal conductance. Neither sapwood density (540–650 kg m⁻³) nor sap velocity differed greatly between regrowth and old stands. At the old forest site, daily transpiration rose from 0.5 mm day⁻¹ in winter to 0.9 mm day⁻¹ in spring–summer, compared to 0.9 mm day⁻¹ and 1.8 mm day⁻¹ at the regrowth site. Annual water use by the overstorey trees was estimated to be ∼230 mm year⁻¹ for the old stand and ∼500 mm year⁻¹ at the regrowth stand, or 20% and 44% of annual rainfall. The overwhelming role of stand sapwood area in determining stand water use, combined with the marked changes in the ratio of sapwood area to basal area with tree age and size, suggest that stand overstorey structure can be managed to alter overstorey water use and catchment water yield. Silviculture to promote old-forest-like attributes may be a viable means of delivering multiple water and conservation benefits.     

Composition and structure of organosolv lignins from four eucalypt species

Lignins were extracted from different species using organosolv process (ethanol/water). Obtained organosolv lignins were characterised by various methods to determine their composition, structure and functional groups with the purpose of evaluating their potential use for obtaining value-added compounds. The purity of organosolv lignins was determined. The total phenols content and the antioxidant power were analysed in order to know the reactivity of lignins. The ratio S/G was determined by nitrobenzene oxidation. In addition, molecular weight distribution, infrared spectroscopy and thermo gravimetrical analysis were carried out in order to determine the physical and chemical properties of organosolv lignins. Obtained organosolv lignins have very high purity and low sugar and inorganic contamination. All organosolv lignins samples have high polydispersity, and lignin from grey ironbark wood had the highest molecular weight average. Among the organosolv lignins, lemon-scented gum showed the highest average value of S/G ratio and the lowest average value of total phenols.