Eucalyptus Stem Research Articles

In vitro evaluation of fungicides against eucalyptus stem canker pathogens in Ethiopia

Field surveys of Eucalyptus camaldulensis diseases were conducted during 2019-20 and 2020-21 in Ethiopia. This species was the most commonly planted in the surveyed fields and exhibited stem canker diseases. Sampling was performed from diseased stems and branches displaying clear symptoms. Morphological and PCR assays of the ITS1 and ITS2 loci were conducted to identify the fungal pathogens. Lasiodiplodia theobromae and Didymella pinodella were identified as the fungal pathogens causing E. camaldulensis stem canker diseases. Four nationally licensed fungicides viz. Vitra (copper hydroxide), Ridomil Gold (metalaxyl-M + mancozeb), Liveshow (pyraclostrobin + epoxiconazole), and Sabozeb (mancozeb) were evaluated for their in vitro control efficacy against the identified fungi at different concentrations (500, 1000, 1500, and 2000 ppm). Vitra and Liveshow were found to be the most effective fungicides at 2000 ppm for the control and treatment of E. camaldulensis stem canker diseases. The identification of L. theobromae and D. pinodella as causal agents of E. camaldulensis is crucial for targeted disease management strategies. The evaluation of four fungicides at different concentrations provided valuable information for selecting the most effective treatment options for practical management practices of the diseases. This research serves as the first report on the management of Eucalyptus disease in Ethiopia, laying the foundation for future studies and contributing to the development of sustainable disease management practices. The findings of this research can guide policymakers, researchers, and agricultural practitioners in implementing targeted fungicide applications to mitigate the impact of stem canker on Eucalyptus plantations and improve their productivity.

Managing ion concentration in sap to control drying collapse, permeability, and streaming potential in plantation-grown eucalyptus timber

Wood is an important renewable resource for a future sustainable bioeconomy. Ion-mediated response in wood is considered a major factor in sap-flow regulation. This study examined the influence of sap replacement with KCl solution and deionised water on drying collapse, wood permeability, and streaming potential of never-dried wood. Volumetric and tangential collapse in KCl-treated Eucalyptus nitens logs decreased significantly by 42%–62% and by 51%, respectively. Improvement in shrinkage properties was concentration-dependent, with a maximum at a concentration (20 mM) in the range of total ionic strength found in living trees. Logs treated with deionised water showed higher normal shrinkage, without affecting collapse. Consistent with reduced collapse in KCl-treated logs, eucalyptus stem cores showing low collapse contained significantly more inorganic cations than the high-collapsed wood. The decrease in collapse when treated with KCl solution coincided with increased green wood permeability. Sap conductivity affected the streaming potential, with the polarity of the induced electric potential varying between concentrations and matching literature reports of electric potential measurements in living trees and laboratory experiments.This study confirmed that drying collapse was negatively correlated to sap conductivity, and potential technological solutions to drying collapse in E. nitens could include sap replacement as a pre-drying treatment, and/or nutrient management of the plantations.

Transcriptome analysis of the transition from primary to secondary growth of vertical stem in Eucalyptus grandis

Eucalyptus was one of the most cultivated hardwood species worldwide, with rapid growth, good wood properties and a wide range of adaptability. Eucalyptus stem undergoes primary growth (longitudinal growth) followed by secondary growth (radial growth), which produces biomass that is an important source of energy worldwide. In order to better understand the genetic regulation of secondary growth in Eucalyptus grandis, Transcriptome analyses in stem segments along a developmental gradient from the third internode to the eleventh internode of E. grandis that spanned primary to secondary growth were carried out. 5,149 genes that were differentially expressed during stem development were identified. Combining the trend analysis by the Mfuzz method and the module-trait correlation analysis by the Weighted Gene Co-expression Network Analysis method, a total of 70 differentially expressed genes (DEGs) selected from 868 DEGs with high connectivity were found to be closely correlated with secondary growth. Results revealed that the differential expression of these DEGs suggests that they may involve in the primary growth or secondary growth. AP1, YAB2 TFs and EXP genes are highly expressed in the IN3, whereas NAC, MYB TFs are likely to be important for secondary growth. These results will expand our understanding of the complex molecular and cellular events of secondary growth and provide a foundation for future studies on wood formation in Eucalyptus.

Soil seed banks provide a storage effect in post-logging regrowth forests of southeastern Australia

Despite the importance of soil seed banks in diversity maintenance, our understanding of plant response to changes in resource availability is largely limited to above-ground vegetation. We investigated how forest structure and edaphic properties influenced the above-ground vegetation and soil seed banks following logging in montane regrowth forests dominated by Eucalyptus regnans in the Central Highlands of southeastern Australia. We surveyed above-ground vegetation, soil seed banks, forest structure and soil properties across 20 harvest units, aged 16 to 20 years. A total of 80 species were identified in above-ground vegetation with 72 species in the soil seed bank, with only 34% of species co-occurring in both species’ pools. Climate, soil, topography, and light availability shaped plant composition but the relative importance of these properties varied among individual species and pools of diversity (combined, above-ground, soil seed bank, life form). Annual heat moisture index (AHMI) was the most important factor that influenced plant community composition across all species pools with individual species positively associated with AHMI. Acacia, but not Eucalyptus stem density further moderated plant response via effects on both light availability and soil nitrogen at the stem exclusion phase of stand development. Structurally mediated controls on above-ground community composition flow through to the soil seed bank via above-ground diversity effects on below-ground composition. For the combined species pool, individual species were most frequently related to Acacia stem density that on average explained 20% of model variation. Soil nutrients accounted for most of the model variation for individual species in above-ground (26%), soil seed bank (20%) and non-woody (32%) pools of diversity, with AHMI accounting for most of the model variation for woody species (18%). The differential response of individual species and community composition to gradients in resource availability across different pools of species diversity and life forms clearly demonstrates a storage effect in wet temperate forests of southeastern Australia that promotes post-disturbance recruitment and persistence. Our work suggests logging interacts with broad environmental controls to shape species diversity. The key role of Acacia stem density as a biotic filter of plant diversity provides opportunity to shape future plant diversity through management interventions such as thinning in the early stages of stand development. With native forest harvesting of these forests set to end from 2024, our findings provide important information on future patterns of plant diversity as logged forests recover over time, opportunities for management interventions in shaping plant composition, and potential impacts of future wildfire.

Statement of Retraction: In vitro assessment of fungicides efficacy against fungal isolates causing eucalyptus stem canker diseases in Ethiopia

Statement of Retraction: In vitro assessment of fungicides efficacy against fungal isolates causing eucalyptus stem canker diseases in Ethiopia

In vitro bioefficacy of Trichoderma species against two Botryosphaeriaceae fungi causing Eucalyptus stem canker disease in Ethiopia

Phytopathogenic fungi, which are leading to significant economic and production losses, pose a serious threat to global forestry. Field surveys were carried out on Eucalyptus trees in Ethiopia between 2019/20 and 2020/21. The E. camaldulensis predominantly grew in the surveyed fields and was severely affected by progressive stem canker disease. The diseased stems and branches exhibiting symptoms were collected, and the Lasiodiplodia theobromae and Neofusicoccum parvum fungal pathogens were identified via morphological and DNA sequence analyses of ITS1 and ITS2 from rDNA. The objective of this research was to assess the in vitro growth inhibition potential of Trichoderma species against Lasiodiplodia theobromae and Neofusicoccum parvum fungal species. Researchers are now exploring alternate eco-friendly management strategies due to the hazardous effects chemical fungicides have on human and environmental health. The use of biocontrol agents, such as Trichoderma species, is one of the potential approaches employed today. The antagonistic activities of Trichoderma asperellum (T4), Trichoderma asperellum (T5), Trichoderma atroviride (T1), Trichoderma atroviride (T11), Trichoderma longibrachiatum (T3), and Trichoderma longibrachiatum (T31) were tested in vitro against Lasiodiplodia theobromae and Neofusicoccum parvum that cause canker disease symptoms in E. camaldulensis. In all antagonism tests, T. asperellum and T. longibrachiatum effectively inhibited the growth of L. theobromae and N. parvum. This implies that the Trichoderma species could be useful to control E. camaldulensis canker disease.

RETRACTED ARTICLE: In vitro assessment of fungicides efficacy against fungal isolates causing Eucalyptus stem canker diseases in Ethiopia

We, the Editors and Publisher of Archives of Phytopathology and Plant Protection have retracted the following article: Wendu Admasu, Assefa Sintayehu & Alemu Gezahgne. In vitro assessment of fungicides efficacy against fungal isolates causing Eucalyptus stem canker diseases in Ethiopia DOI: 10.1080/03235408.2022.2140468. Volume 55, 2022–Issue 18 Since publication, concerns have been raised about the integrity of the data presented in the article. These concerns relate specifically to the images in Figures 1 and 3. Figure 1, Control, top row, and Control, bottom row, are duplicated. Figure 3, L1500ppm and V1500ppm are duplicated. Figure 3, Control, top row, and Control, third row, are duplicated. Figure 3, R1000ppm and S500ppm are duplicated. Figure 3, R1500, R2000ppm, and S2000ppm are duplicated. Figure 3, Control, second row, and Control, bottom row, are duplicated. When approached for an explanation, the authors have been unable to address the concerns raised and have not been able to provide sufficient original data from their study. As verifying the validity of published work is core to the integrity of the scholarly record, we are therefore retracting the article. The authors listed in this publication have been informed and agree with the retraction. We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Survey and Identification of Didymellaceae Causing Stem Canker Disease of Eucalyptus (E. camaldulensis) in Ethiopia

Plantation forests are established by planting Eucalyptus tree species to provide timber and pulp for the construction industries and to meet the energy needs in Ethiopia. Besides the extensive Eucalyptus plantations in the country, fungal pathogen-related diseases are the main challenges to successful production and management. The disease survey was conducted in the Eucalyptus growing areas of Ethiopia during 2019/2020 and 2020/2021. The objective of this research was to assess the diseases associated with Eucalyptus plant species and identify the causal fungal species. Plants of E. camaldulensis were the dominant species in the survey fields and were severely associated with stem and branch canker diseases. Diseased samples were collected and fungal species were identified as Didymellaceae according to culture morphology and affirmed by internal transcribed spacer sequence analysis. In phylogeny, isolates in the study and a reference strain formed supportive monophyletic clades with strong 90% and 95% support with Didymella coffeae-arabicae and Didymella pinodella respectively. Pathogenicity tests revealed that Didymellaceae could infect E. camaldulensis. The findings are the first reports of Eucalyptus stem canker disease caused by Didymellaceae in Ethiopia.

Unveiling the Secretome of the Fungal Plant Pathogen Neofusicoccum parvum Induced by In Vitro Host Mimicry

Neofusicoccum parvum is a fungal plant pathogen of a wide range of hosts but knowledge about the virulence factors of N. parvum and host–pathogen interactions is rather limited. The molecules involved in the interaction between N. parvum and Eucalyptus are mostly unknown, so we used a multi-omics approach to understand pathogen–host interactions. We present the first comprehensive characterization of the in vitro secretome of N. parvum and a prediction of protein–protein interactions using a dry-lab non-targeted interactomics strategy. We used LC-MS to identify N. parvum protein profiles, resulting in the identification of over 400 proteins, from which 117 had a different abundance in the presence of the Eucalyptus stem. Most of the more abundant proteins under host mimicry are involved in plant cell wall degradation (targeting pectin and hemicellulose) consistent with pathogen growth on a plant host. Other proteins identified are involved in adhesion to host tissues, penetration, pathogenesis, or reactive oxygen species generation, involving ribonuclease/ribotoxin domains, putative ricin B lectins, and necrosis elicitors. The overexpression of chitosan synthesis proteins during interaction with the Eucalyptus stem reinforces the hypothesis of an infection strategy involving pathogen masking to avoid host defenses. Neofusicoccum parvum has the molecular apparatus to colonize the host but also actively feed on its living cells and induce necrosis suggesting that this species has a hemibiotrophic lifestyle.

Stem rot of eucalyptus cuttings caused by Neopestalotiopsis spp. in Brazil

AbstractIn Brazil, the fungus Neopestalotiopsis (= Pestalotiopsis) is known to cause disease in eucalyptus cuttings. However, although it occurs relatively frequently in cutting nurseries, the pathogenic species have yet to be identified. Thus, the aim of the present work was to perform a morphological and phylogenetic characterization to identify the aetiological agent. For this purpose, the isolates were subjected to a multilocus analysis using the two gene regions β‐tubulin (TUB) and the translation elongation factor (TEF). Based on the genomic sequences, two known species and one new species of the pathogen were identified. After confirmation of their pathogenicity, N. australis was confirmed as a new report in eucalyptus. Neopestalotiopsis rosae failed to differ from the control, however, showed internal and external lesion in eucalyptus stem. In addition, in this study, a new species called N. eucalypti was described, causing disease in hybrids eucalyptus. Morphological characterization allowed for the confirmation of the N. australis and N. rosae isolates, primarily based on differences in the size and shape of the conidia. For N. eucalypti, no morphological marker was found that separated it from the other species within the genus. The results confirm the existence of at least three Neopestalotiopsis species as aetiological agents of leaf spot and stem rot in eucalyptus cuttings in Brazil.

Effect of stand density on longitudinal variation of wood and bark growth in fast-growing Eucalyptus plantations

Abstract: The influence of tree spacing on the wood/bark ratio is unknown in young fast-growing Eucalyptus trees. The objective of this study was to evaluate the effect of plant spacing on the wood and bark production along the Eucalyptus stem. Four genetic materials were planted in four spacings: 3×1 m, 3×2 m, 3×3 m and 3×4 m. Three 5-year-old trees from each clone and in each plant spacing were harvested. Cross-sectional discs (thickness: 30 mm) were cut from each tree along the stem (0%, 25%, 50%, 75% and 100% of the total tree height) and at 1.3 m above ground, totaling 288 disks (4 spacings × 4 clones × 3 replicates × 6 axial positions). The wood thickness was measured at six random and equidistant points around the perimeter using a gauge and means were calculated from each disc. Six cross diameters were measured for each debarked disc. After obtaining the averaged bark thickness and wood diameter, the bark content was calculated as the ratio between the surface area occupied by the bark and the total area of the stem in each level. In the narrowed plant spacing (3×1), the trees had a mean diameter of 7.4 cm, while at the spacing 3×4 the diameter of the trees was 91% higher (14.11 cm) at breast height. The increase in plant spacing from 3 to 12 m2 per tree resulted in an increase in bark thickness (56.7%) from 1.94 mm to 3.04 mm, but caused a reduction of bark content (16%) from 9.66% to 8.11%. Our findings show that trees grown under wider spacing tend to produce thicker bark. The bark thickness and the effect of plant spacing on the bark thickness decreased in the base-top direction. The correlation between bark thickness and wood diameter increases from 0.682 to 0.825 with the increase of spacing between trees. In contrast, the bark thickness to bark content correlation decrease from 0.735 to 0.15 with increased plant spacing. The stand density significantly affected the variation of the stem diameter, bark thickness and bark content of Eucalyptus plantations.

Genomic characterization of mating type loci and mating type distribution in two apparently asexual plantation tree pathogens

The Eucalyptus stem canker pathogens Teratosphaeria gauchensis and T. zuluensis (Capnodiales, Teratosphaeriaceae) are found in many tropical regions of the world where their hosts are cultivated for plantation forestry. Population genetic analyses have suggested that some populations undergo recombination, even though their sexual states have never been observed. Against this background, the aim of this study was to characterize the mating type (MAT) locus of these species and thus to better understand the basis of their diversity. Known Mycosphaerellaceae MAT genes were used to identify and investigate the MAT locus in the T. gauchensis and T. zuluensis genomes. Both species were found to be heterothallic and primers were designed to amplify the opposite MAT idiomorphs as well as conserved regions within the MAT1‐1‐1 and MAT1‐2‐1 genes. Each Teratosphaeria MAT idiomorph was defined by either the MAT1‐1‐1 or the MAT1‐2‐1 gene, and an idiomorph‐specific hypothetical protein (MAT1‐1‐10 and MAT1‐2‐12). Populations of T. zuluensis from Asia and southern Africa were dominated by a single mating type, whereas the proportions of the different idiomorphs for T. gauchensis in South America and southern Africa were similar. There was no physical evidence of sexual reproduction for either species and it is argued that although recombination may be possible, it is unlikely to form an important part of their life cycles in diseased Eucalyptus plantations. Instead, continuous human‐mediated multiple introductions of these species have probably resulted in the current genetic structure of their populations, which holds risk for future disease outbreaks and interspecific hybridization.

Three genetic groups of the Eucalyptus stem canker pathogen Teratosphaeria zuluensis introduced into Africa from an unknown source.

The Eucalyptus stem canker pathogen Teratosphaeria zuluensis was discovered in South Africa in 1988 and it has subsequently been found in several other African countries as well as globally. In this study, the population structure, genetic diversity and evolutionary history of T. z uluensis were analysed using microsatellite markers to gain an enhanced understanding of its movement in Africa. Isolates were collected from several sites in Malawi, Mozambique, Uganda and Zambia. Data obtained were compared with those previously published for a South African population. The data obtained from 334 isolates, amplified across eight microsatellite loci, were used for assignment, differentiation and genetic diversity tests. STRUCTURE analyses, θ st and genetic distances revealed the existence of two clusters, one dominated by isolates from South Africa and the other by isolates from the Zambezi basin including Malawi, Mozambique and Zambia. High levels of admixture were found within and among populations, dominated by the Mulanje population in Malawi. Moderate to low genetic diversity of the populations supports the previously held view that the pathogen was introduced into Africa. The clonal nature of the Ugandan population suggests a very recent introduction, most likely from southern Africa.

High population diversity and increasing importance of the Eucalyptus stem canker pathogen, Teratosphaeria zuluensis, in South China

Coniothyrium stem canker, caused by Teratos- phaeria zuluensis, is one of the most important diseases of plantation-grown Eucalyptus trees in tropical and sub- tropical areas of the world. Previous research on the population structure of T. zuluensis in China, Malawi and South Africa has suggested that T. zuluensis in these countries had independent origins, with the highest genetic diversity found in a population from South China. In this study, the genetic diversity of three T. zuluensis populations from different regions in South China was determined using ten microsatellite markers. Results showed that more than one genotype of T. zuluensis can occur on a single tree in all three populations and that a moderate to high genetic diversity exists within the populations. Population differen- tiation was evident between populations, and in one population there was evidence for a low level of genetic recombination. Comparisons among the three populations ofT. zuluensis from South China suggest that they originated independently of each other.

Solid Phase Extraction of Lead(II) by Sorption on Grinded Eucalyptus Stem and Determination with Flame Atomic Absorption Spectrometry

AbstractA sensitive and simple solid‐phase preconcentration procedure for the determination of trace amount of lead by flame atomic absorption spectrometry (FAAS) is developed. The method is based on the adsorption of Pb2+ on the column of fine grinded eucalyptus stem adsorbent, elution of the column by nitric acid and subsequent determination by FAAS. The effect of different variables such as pH, eluent type, flow rate and interfering ions on the recovery of the analyte was investigated and optimum conditions were established. The adsorption of lead onto fine grinded eucalyptus stem can formally be described by a Langmuir equation with a maximum adsorption capacity of 4.49 mg g−1. A preconcentration factor of 50 was achieved using the optimum conditions. The calibration graph was linear in the range 10–125 ng mL−1 of lead in the initial solution with r = 0.9982. The limit of detection based on 3Sb criterion was 4.5 ng mL−1 and the relative standard deviation for eight replicate measurements of 30 and 80 ng mL−1 of iron was 3.6 and 2.8%, respectively. The method was successfully applied to the determination of lead added to well, tap and wastewater samples.

Multi-gene phylogenies and phenotypic characters distinguish two species within the Colletogloeopsis zuluensis complex associated with Eucalyptus stem cankers

Colletogloeopsis zuluensis, previously known as Coniothyrium zuluense, causes a serious stem canker disease on Eucalyptus spp. grown as non-natives in many tropical and sub-tropical countries. This stem canker disease was first reported from South Africa and it has subsequently been found on various species and hybrids of Eucalyptus in other African countries as well as in countries of South America and South-East Asia. In previous studies, phylogenetic analyses based on DNA sequence data of the ITS region suggested that all material of C. zuluensis was monophyletic. However, the occurrence of the fungus in a greater number of countries, and analyses of DNA sequences with additional isolates has challenged the notion that a single species is involved with Coniothyrium canker. The aim of this study was to consider the phylogenetic relationships amongst C. zuluensis isolates from all available locations and to support these analyses with phenotypic and morphological comparisons. Individual and combined phylogenies were constructed using DNA sequences from the ITS region, exons 3 through 6 of the beta-tubulin gene, the intron of the translation elongation factor 1-alpha gene, and a partial sequence of the mitochondrial ATPase 6 gene. Both phylogenetic data and morphological characteristics showed clearly that isolates of C. zuluensis represent at least two taxa. One of these is C. zuluensis as it was originally described from South Africa, and we provide an epitype for it. The second species occurs in Argentina and Uruguay, and is newly described as C. gauchensis. Both fungi are serious pathogens resulting in identical symptoms. Recognising them as different species has important quarantine consequences.

Within-tree transcriptome profiling in wood-forming tissues of a fast-growing Eucalyptus tree

Despite the availability of high-throughput transcript profiling technology, little is known about tissue-specific gene expression patterns in the wood-forming tissues of Eucalyptus plantation tree species. We used cDNA-amplified fragment length polymorphism (AFLP) analysis in combination with infrared fragment detection and semi-automated band quantification to profile gene expression in a 6-year-old, fast- growing Eucalyptus tree. The expression profiles of 6385 transcript-derived fragments (TDFs) were analyzed across four major woody tissues (mature xylem, immature xylem, phloem and cork) collected from two stem positions, to provide a global view of transcript abundance and variability in the Eucalyptus stem. About 21% of the TDFs were differentially expressed and could be grouped into clusters representing co- expressed genes. A total of 71 TDFs representing different gene clusters were isolated and characterized. These included genes implicated in cell fate, signal transduction and cell wall biosynthesis, processes closely associated with xylogenesis. Analysis of the expression levels of selected TDFs by quantitative RT-PCR corroborated the TDF quantification and confirmed that cDNA-AFLP analysis is a highly efficient and accurate tool for transcript profiling and gene discovery in wood-forming tissues of tree species.

Development of polymorphic microsatellite markers for the fungal tree pathogen Cryphonectria eucalypti

AbstractPolymorphic microsatellite DNA markers were developed from a single spore isolate of Cryphonectria eucalypti collected from a Eucalyptus stem canker in South Africa. Markers were obtained using the enrichment technique known as fast isolation by AFLPs of sequences containing repeats (FIASCO). Ten polymorphic markers were isolated, of which, two were discarded due to their high polymorphism in the flanking region. The mean number of alleles produced by the remaining eight markers from 20 isolates was 7.25, and alleles per locus ranged from four to 12. The markers will be used to study populations of C. eucalypti.

Twenty years of stand development in pure and mixed stands of Eucalyptus saligna and nitrogen-fixing Facaltaria moluccana

Abstract The vast majority of tropical tree plantations are monocultures, and only a few case studies have examined growth of mixed-species plantations. Mixtures that contain nitrogen (N)-fixing species may have the potential to increase overall plantation yields, but too few case studies are available to provide general insights. We extended previous measurements of 10 years of stand development in a mixed-species experiment in Hawaii through age 20 years. The plots had a constant total number of stems initially (2500 ha−1), but varying ratios of Eucalyptus saligna (Sm.) to nitrogen-fixing Facaltaria moluccana (Miquel) Barneby & Grimes (=Albizia Facaltaria (L.) Fosberg, and Paraserianthes Facaltaria (L.) I. Nielsen). Eucalyptus stem growth declined strongly in monocultures after age of 7 years, but showed no decline in mixtures. After 10 years of stand development, Eucalyptus stem mass was greatest in the monoculture, averaging about 155 Mg/ha (versus 140 Mg/ha in the 0.5 Facaltaria treatment); total (combined) stem mass for both species was almost twice as great in mixtures as in monocultures. By the age of 20 years, Eucalyptus stem mass was within a 20% range across treatments (260 Mg/ha), and total stem mass ranged up to 430 Mg/ha in the 0.75 Facaltaria treatment. Losses of stem mass from mortality were moderate for Eucalyptus between 18 and 20 years, averaging 20–25% of gross stem growth in mixed-species treatments, but 60% in the Eucalyptus monoculture. Mortality losses of stem mass were extremely high for Facaltaria in all plots, matching or exceeding gross stem growth from age 18 to 20 years. The size of individual Eucalyptus trees was much greater in the mixed plots than in the monoculture plots, so any short-term economic gain from the mixed-species plots may derive from larger tree sizes rather than from more wood mass per hectare. The longer term benefits of mixed plots may include the effects of Facaltaria on soil fertility and community diversity. Overall, these very large changes in ecosystem production in mixtures underscores the need for a large number of additional studies to examine other species combinations, sites, and silvicultural systems.

Morphological and molecular relatedness of geographically diverse isolates of Coniothyrium zuluense from South Africa and Thailand

Coniothyrium canker, caused by Coniothyrium zuluense, is a serious stem canker disease of Eucalyptus in subtropical parts of South Africa. A Coniothyrium associated with similar symptoms to those in South Africa was observed on E. camaldulensis in 1996 in Thailand. It was previously thought that C. zuluense was restricted to South Africa. This study compares South African isolates of C. zuluense with isolates of the Coniothyrium from Thailand. Results of morphological comparisons indicate that the South African and Thailand isolates are the same. This was further confirmed when all Coniothyrium isolates associated with stem cankers on Eucalyptus spp. grouped together in a single major clade for both rDNA sequence data and AFLP analysis. This clade was distant from isolates of other Coniothyrium spp. included for comparative purposes. Although the Coniothyrium isolates from South Africa and Thailand resided in two separate clades, these were closely related and, we believe that the isolates from Thailand represent C. zuluense. This is the first record of the important Eucalyptus stem canker pathogen outside South Africa.