Eucalyptus Species Research Articles

Detection of Irrigated and Non-Irrigated Soybeans Using Hyperspectral Data in Machine-Learning Models

The objectives of this work are (i) to classify soybean cultivars under different irrigation managements using hyperspectral data, looking for the best machine-learning algorithm for the classification and the input that improves the performance of the models. The experiment was implemented in the 2023/24 harvest in the experimental area of the Federal University of Mato Grosso do Sul, Câmpus Chapadão do Sul, Mato Grosso do Sul, and it was conducted in a strip scheme with seven cultivars subjected to irrigated and rainfed management. Sixty days after crop emergence, three leaves per plot were collected for evaluation by the hyperspectral sensor. The spectral data was then separated into 28 bands to reduce dimensionality. In this way, two databases were generated: one with all the spectral information provided by the sensor (WL) and one with the 28 spectral bands (SB). Each database was subjected to different machine-learning models to ascertain the improved accuracy of the models in distinguishing the different eucalyptus species. The models tested were artificial neural networks (ANN), decision trees (DT), linear regression (LR), M5P algorithm, random forest (RF), and support vector machine (SVM). The results demonstrate the effectiveness of machine-learning models in differentiating soybean management under rainfed and irrigated conditions, highlighting the advantage of hyperspectral data (WL) over selected spectral bands (SB). Models such as the support vector machine (SVM) showed the best levels of accuracy when using the entire available spectrum. On the other hand, artificial neural networks (ANN) performed well with spectral band data, demonstrating their ability to work with smaller data sets without compromising the classification.

New Eucalyptus (Myrtaceae) species host of Blastopsylla occidentalis (Hemiptera: Aphalaridae) and its parasitism by Psyllaephagus blastopsyllae (Hymenoptera: Encyrtidae) in Indonesia

Blastopsylla occidentalis Taylor (Hemiptera: Aphalaridae), native to Australia, causes damage to an increasing number of Eucalyptus (Myrtaceae) species and their hybrids in a growing number of countries. This is partly because predatory insects and spiders have low potential to reduce B. occidentalis populations. The purpose of this study was to report a new host of B. occidentalis and the parasitism of this insect by Psyllaephagus blastopsyllae Tamesse, Soufo, Tchanatame, Dzokou, Gumovsky, & Coninck (Hymenoptera: Encyrtidae) in Indonesia. Blastopsylla occidentalis nymphs parasitized were collected from five Eucalyptus pellita F. Muell. trees on October 3rd, 2023, in Senoni, East Kalimantan, Indonesia, and reared in a laboratory until their adults or P. blastopsyllae emerged. The adults recovered from this parasitoid were identified by morphological analysis of their bodies. Eucalyptus pellita is a new host for B. occidentalis. This is the first time in Asia (Indonesia) that P. blastopsyllae has been reported. This new insect-host association alerts the world to the need to develop management strategies for B. occidentalis on E. pellita plantations. The recovery of P. blastopsyllae also opens up new perspectives for the development of biological control programs in Indonesia.

Fossil insect-feeding traces indicate unrecognized evolutionary history and biodiversity on Australia's iconic Eucalyptus.

Fossilized plant-insect herbivore associations provide fundamental information about the assembly of terrestrial communities through geologic time. However, fossil evidence of associations originating in deep time and persisting to the modern day is scarce. We studied the insect herbivore damage found on 284 Eucalyptus frenguelliana leaves from the early Eocene Laguna del Hunco rainforest locality in Argentinean Patagonia and compared damage patterns with those observed on extant, rainforest-associated Eucalyptus species from Australasia (> 10 000 herbarium sheets reviewed). In the fossil material, we identified 28 insect herbivory damage types, including 12 types of external feeding, one of piercing-and-sucking, five of galls, and 10 of mines. All 28 damage types were observed in the herbarium specimens. The finding of all the fossil damage types on extant Eucalyptus specimens suggests long-standing associations between multiple insect herbivore lineages and their host genus spanning 52 million years across the Southern Hemisphere. This long-term persistence, probably enabled through niche conservatism in wet eucalypt forests, demonstrates the imprint of fossil history on the composition of extant insect herbivore assemblages. Although the identities of most insect culprits remain unknown, we provide a list of Eucalyptus species and specific population locations to facilitate their discovery, highlighting the relevance of fossils in discovering extant biodiversity.

Allelopathic effects of leaf extracts of Eucalyptus camaldulensis Dehnh. on morphological, physiological, and yield traits of Ethiopian wheat (Triticum durum L.) cultivars

Allelochemicals released into the soil from the leaves of eucalyptus species affect the growth and physiology of various crops. This study aimed to evaluate the allelopathic effects of aqueous and methanolic leaf extracts from Eucalyptus camaldulensis on three Ethiopian wheat cultivars (Assasa, Mukiye and Ude) of Triticum durum L. It was conducted as a pot experiment, and it utilized four concentrations of the extracts (Control (0%), 10%, 15%, and 20%) in a completely randomized design with three replicates. Results indicated that both extracts inhibited plant growth, biomass, and yield, with the methanolic extract showing stronger inhibitory effects. For instance, a concentration of 20% methanolic leaf extracts decreased chlorophyll fluorescence in the Assasa, Ude, and Mukiye cultivars by 53.97%, 36.36%, and 36.51%, respectively. The growth of both shoots and roots in Assasa, Ude, and Mukiye was significantly reduced at higher concentrations. Increasing concentrations of the extracts led to greater reductions in seedling traits and overall crop yield, with significant impacts observed (p ≤ 0.05). The findings suggest that eucalyptus should not be planted on agricultural land due to its negative impact on crop productivity.

Optimization of RNA extraction protocol from Eucalyptus and Populus species for gene expression studies

ABSTRACT Extraction of high-quality RNA is complicated due to the presence of polysaccharides and polyphenols in woody plant species like Eucalyptus and Populus. To conduct gene expression studies, RNA must be of high quality and intact integrity. Although, RNA extraction kits make the process quick and easy but they might not consistently provide high-quality RNA from Eucalyptus and Populus. Therefore, the primary objective of this work is to optimize a repeatable and systematic CTAB method for RNA extraction of high quality from Populus and Eucalyptus leaves. According to the study results, the optimized CTAB approach is more suitable for these plant species than RNA extraction kits. The agarose gel electrophoresis demonstrated that the RNA samples retained their integrity due to the presence of distinct 28S and 18S rRNA bands. Additionally, the RNA integrity number was found to be between 7.2 and 8.0. As indicated by the A260/A280 ratios, the optimized method’s RNA extraction yielded minimal levels of polysaccharide and polyphenol contamination. For Eucalyptus, the absorbance values ranged from 1.98 to 1.99 while for Populus it was 1.97 to 1.98. Similarly, the A260/230 ratios, which represent the second indicator of nucleic acid purity, were found to be 2.01 to 2.08 and 2.02 to 2.09 for Eucalyptus and Populus, respectively. The high-quality RNA was shown to be appropriate for use in further processes, such as cDNA synthesis, gene amplification, and real-time quantitative PCR (RT-qPCR).

Thicker or Shorter Bark Fragments of Eucalypt Tree Species Make More Densely Packed Fuel Beds, Which Slow Down Fire Spread

Many eucalypt trees shed their bark annually. This bark becomes a component of the litter layer, which acts as fuel, especially during surface fires. The amount and quality of shed bark vary greatly among species, which might have important effects on forest surface fire behavior. In this study, we aimed to compare the bark fuel bed flammability of eight eucalypt tree species and tried to link their bark litter traits via the surface fuel bed structure to bark flammability. In controlled laboratory burns, three flammability parameters, the fire spread rate, total burning time, and maximum temperature, were measured. The bark litter traits included length, curliness, thickness, dry matter content, tissue density, carbon content, nitrogen content, and terpene content, while the litter bed packing ratio and packing density were also measured. We found significant differences in bark traits and flammability among species. Thicker bark fragments of the eucalypt tree species had higher packing densities in fuel beds, a slower fire spread, and a longer burning time. This relationship was strongly driven by the thick bark fragments of Eucalyptus punctata DC. Still, also within the other seven species, bark thickness was the strongest predictor of bark fuel bed flammability, with some additional explanatory power for bark length. For the first time, our study demonstrates that bark traits, particularly litter fragment thickness and length, drive bark litter flammability of eucalypt tree species through their effects on bark fuel bed structure. These findings contribute to our understanding and predictive power of wildfire behavior in forest stands dominated by different eucalypt species.

Seasonal and Spatial Dynamics of Fungal Leaf Endophytes in Eucalyptus crebra (Narrow-Leaved Ironbark)

Fungal endophytes play an important role in improving the health and productivity of native and cultivated plant species. Despite their ecological and industrial importance, few eucalypt species have been studied in terms of their endophyte communities. We examined the seasonal and spatial dynamics of fungal leaf endophytes in the model species, Eucalyptus crebra (narrow-leaved ironbark), using ITS-based amplicon sequencing. Alpha and beta diversity analyses revealed significantly higher species richness in summer compared to autumn and spring. Similarly, two-way ANOVA analysis showed significantly higher species diversity in summer compared to autumn (observed p < 0.001, Chao1 p < 0.005) and spring (observed p < 0.005, Chao1 p < 0.005). No difference in Shannon index was observed among different canopy levels across the season. Beta-diversity showed differences in fungal composition across the seasons and at various canopy levels based on unweighted UniFrac distance metric (PERMANOVA season p < 0.001, canopy p < 0.05), signifying distinct separation of fungi based on presence-absence. Ascomycota was the most abundant and diverse phylum and was present throughout the year. In contrast, Basidiomycota was only observed during cooler and drier seasons. Neofusicoccum was the most abundant genus, but distribution fluctuated significantly across the seasons. Pestalotiopsis and Neopestalotiopsis were most abundant in the low leaf canopy, whereas Pseudosydowia was most abundant in the high canopy. This study indicates that the diversity and abundance of endophytic fungi in the leaves of healthy E. crebra trees fluctuate seasonally and across canopy levels. The data generated can be used as a baseline for assessing and potentially modulating the health of E. crebra and other important Eucalyptus spp.

Definition of reproductive structures in Eucalyptus for phenological data collection.

In an era where global climate change is shifting plant phenology, global meta-analyses of multiple species are required more than ever. Common language or references for enhanced data compatibility are key for such analyses. Although the Plant Phenology Ontology (PPO) addresses this challenge, it does not capture several relevant reproductive structures that are critical in species with long reproductive cycles, like many Eucalyptus species. We reviewed the terminology and concepts that describe reproductive structures in eucalypts and compared them with the existing classes of the PPO to explore the PPO's potential for harmonizing disparate eucalypt datasets. We identified incongruencies within and between eucalypt terminology and the PPO. We tested the sensitivity of the PPO for capturing key eucalypt phenological structures and found it sensitive to classification of certain structures. To address these limitations, we developed the Eucalyptus Phenology Ontology (EPO), a new ontology that builds on the PPO and captures key reproductive structures using a more refined classification. The EPO integrates the relationships between reproductive structures, phenological stages, and phenological traits. The vocabulary is species-neutral so it can be applied to other taxa but specifies the synonyms and descriptions required to capture the complexity of eucalypt phenology.

Differential eco-physiological performance of eight Eucalyptus species grown in Tunisian’s arid regions

Successful production of Eucalyptus in drylands requires a thorough understanding of the mechanisms involved in their tolerance to abiotic stress as well as drought. The present study aimed to investigate the effects of dry conditions on morpho-physiological characteristics of eight 5-year-old Eucalyptus species trees, Eucalyptus camaldulensis Dehn., Eucalyptus gomphocephala DC., Eucalyptus torquata Luehm., Eucalyptus microtheca F.Muell., Eucalyptus occidentalis Endl., Eucalyptus diversifolia Bonpl., Eucalyptus sargentii Maiden., and Eucalyptus torwood (Spontaneous hybrid), grew in the same arid microhabitat (a plot) characterized by poor soil. The experiments were conducted in summer 2022, a year that was characterized by a low rainfall rate. Thus, at regular intervals, several parameters were assessed. Plant water status, leaf water relations, gas exchanges, and chlorophyll fluorescence in relation to trees growth performance and leaf traits. Results revealed a distinct resistance level to aridity for the studied species, trees were able to grow showing a clear inter-specific variability. Regarding all species, E. camaldulensis, exhibited a particular behavior to preserve their internal functionality. It displayed simultaneously a rapid growth performance with an ability to develop thinner leaves and earlier stomatal closure under water deficit. Although, E. microtheca, E. gomphocephala, and E. diversifolia’ growth were low, but trees attempted to maintain a stable inter-dependence functions for survival. For E. occidentalis, E. torquata, E. sargentii, and E. torwood, we suggest that a physiological acclimation took place under severe conditions, they showed convergence responses for many parameters. Their ability to maintain good leaves’ succulence and thickness is clearly attributed to a significant RWC (71.5% to 82.4%) related to important LTD, LDMC, and SLW, enabling trees to have important stomata conductance and maintain respectful growth performance. Overall, this comparative study of multiple Eucalyptus species revealed significant variability in their functional and adaptive responses to water deficiency and dry weather conditions, which aids in selecting species that are more appropriate to arid natural environments.

Assessment of the bonding quality of Toona ciliata (Australian cedar) lamellas for glulam beams produced with different adhesives and surface finishes

Glued laminated timber (Glulam) is an engineered structural product manufactured based on quality control. Although its production is generally carried out with pine and eucalyptus species, scientific studies have dedicated time to investigate the possibility of using other species from reforestation. Although some species of Australian cedar have been studied, the Toona ciliata has not yet been applied for the production of glulam. In addition to timber selection, the specification of adhesive used to glue lamellas that does not emit formaldehyde has also aroused the interest of researchers. For this purpose, two-component polyurethane adhesive based on vegetable oils has been presented as a potential alternative for resorcinol-formaldehyde, which is commonly used in the glulam manufacturing. In addition, it was also noticed that execution of surface finish (sanding) on lamellas has not been target of researches concerning gluing performance. Therefore, the purpose of this study was to evaluate the effect of different combinations of adhesive (two-component polyurethane and resorcinol-formaldehyde) and finishing (planing and sanding with 80-, 120- and 220-grid) on delamination and shear strength of glue line between Australian Cedar lamellas. All adhesive-finish combinations presented some percentage of delamination within the limit permitted for hardwoods (ABNT NBR 7190-6). The predominant mode of rupture was wood failure, which highlights the potential for using Australian Cedar timber and vegetable oil-based adhesive in the production of glulam elements.

Socio-economic contribution of eucalyptus species on the livelihood of small-holder growers in horro buluk woreda, Oromia, Ethiopia

Socio-economic contribution of eucalyptus species on the livelihood of small-holder growers in horro buluk woreda, Oromia, Ethiopia

Exogenous silicon alleviates aluminum stress in Eucalyptus species by enhancing the antioxidant capacity and improving plant growth and tolerance quality

BackgroundAs an efficient and high-quality additive in agriculture and forestry production, silicon (Si) plays an important role in alleviating heavy metal stress and improving plant growth. However, the alleviating effect of aluminum (Al) toxicity by Si in Eucalyptus is still incomplete.ResultsHere, a study was conducted using two Al concentrations (0 and 4.5 mM) with four Si concentrations (0, 0.5, 1, and 1.5 mM) to investigate plant growth, tolerance and antioxidant defense system in four Eucalyptus species (Eucalyptus tereticornis, Eucalyptus urophylla, Eucalyptus grandis, and Eucalyptus urophylla × Eucalyptus grandis). The results showed that the stress induced by 4.5 mM Al increased oxidative damage, disturbed the balance of enzymatic and non-enzymatic antioxidant systems, and negatively affected plant growth and tolerance quality in the four Eucalyptus species. However, the addition of 0.5 mM and 1 mM Si alleviated the effects of Al toxicity on plant growth and improved plant growth quality by strengthening stress tolerance. Besides, adding Si significantly facilitated the synergistic action of enzymatic and non-enzymatic antioxidant defenses, increased the removal of reactive oxygen species, reduced lipid peroxidation, and oxidative stress, and promoted the phytoremediation rate of the four Eucalyptus species by 18.7 ~ 34.8% compared to that in the absence of Si.ConclusionsSilicon can alleviate the effect of Al toxicity by enhancing the antioxidant capacity and improving plant growth and tolerance quality. Hence, the application of Si is an effective method for the phytoremediation of Eucalyptus plantations in southern China.

POTENTIAL USE OF Pinus patula WOOD FOR THE PRODUCTION OF PURE AND IN COMBINATION WITH Eucalyptus PLYWOOD PANELS

Plywood panels are products of great importance in the global market, and Brazil is a large producer of conifer plywood, which boosts industrial activities in the south of the country and consequently contributes to the Brazilian GDP. Pinus patula is an unconventional species that requires study for this purpose. Thus, this research aimed to evaluate the potential for using Pinus patula wood for the production of pure plywood panels and in combination with Eucalyptus grandis and Eucalyptus dunnii. 8 treatments were produced, pure and in combination of species, which were glued with phenol formaldehyde adhesive, in a grammage of 180 g/m2 and a solids content from the adhesive formulation of 34%, and pressed at a temperature of 140°C for 13 minutes at a specific pressure of 11 kgf/cm2. Pinus taeda was used as a reference species. The physical and mechanical properties were evaluated according to the ABNT NBR 17002 and ABNT ISO 12466 standards. The results demonstrated that, for the majority of the properties evaluated, the Pinus patula panels were statistically equal or superior in relation to Pinus taeda. The “combi” type panels showed that the Eucalyptus species contributed to improving the static bending property. It is concluded, therefore, that Pinus patula has potential for the production of plywood panels, allowing an increase in the availability and diversity of raw materials for industrial processes, and that the static bending property can be improved with the production of panels of the “combi'' type using Eucalyptus veneers.

Climate change favors expansion of three Eucalyptus species in China.

Eucalyptus has become one of the most widely planted species in tropical and subtropical regions in China, with important economic, ecological, and social values. However, it is currently unclear how climate change will affect different Eucalyptus species. Therefore, it is urgent to investigate the potential distribution and dynamics of Eucalyptus under current and future climate scenarios. In this study, we analyzed the potential distribution patterns of the three main Eucalyptus species (Eucalyptus grandis, Eucalyptus urophylla, and Eucalyptus tereticornis) under current and future climatic conditions (2041-2060 and 2061-2080) using the optimized MaxEnt model, which integrates a variety of environmental data including climate, topography, soil, and human influence. We also identified the main factors affecting the potential distributions of the three main Eucalyptus species. The model indicated that E. grandis exhibited heightened sensitivity to the mean temperature of the coldest quarter (7.0-20.0 °C) and annual mean temperature (11.9-24.2 °C), whereas E. urophylla displayed heightened sensitivity to precipitation of the warmest quarter (272-1694mm) and annual precipitation (812-2624mm). Conversely, E. tereticornis demonstrated heightened sensitivity to annual mean temperature (12.7-24.5°C) and temperature seasonality (63.8-598.9). Under the current climate, E. tereticornis had the widest suitable distribution area (124.91 × 104 km²), followed by E. grandis (124.89 × 104 km²) and E. urophylla (119.81 × 104 km²). Under future climate change scenarios, the suitable ranges of E. grandis, E. urophylla and E. tereticornis will continue to expand. This study highlights the importance of climate change in Eucalyptus distribution and provides quantified potential distribution maps for three Eucalyptus species under current and future climate conditions in China. This research offers valuable scientific insights pertinent to the management and rational site selection for Eucalyptus plantations.

Regeneration and Genetic Transformation in Eucalyptus Species, Current Research and Future Perspectives

Eucalyptus is an important plantation tree with a high economic value in China. The tree contributes significantly to China’s timber production. The stable and efficient Eucalyptus regeneration system and genetic transformation system are of great significance for exploring the regulatory function and possible genetic breeding capacity of important genes in the species. However, as a woody plant, Eucalyptus has problems, such as a long generation cycle, strong specificity of the regeneration system, and a low genetic conversion rate, which seriously limit the rapid development of Eucalyptus genetics and breeding programs. The present review summarizes the status of research on Eucalyptus regeneration and genetic transformation, with a focus on the effects of explants, media, plant growth regulators (PGRs), and concentrations in the Eucalyptus regeneration process. In addition, the effects of genotype, Agrobacterium, antibiotics, preculture, and co-culture on the genetic transformation efficiency of Eucalyptus are discussed. Furthermore, the study also summarizes the problems encountered in Eucalyptus regeneration and genetic transformation, with reference to previous studies, and it outlines future developments and prospects. The aim was to provide a reference for solving the problems of genetic instability and the low transformation efficiency of eucalyptus, and to establish an efficient and stable eucalyptus regeneration and transformation system to accelerate the process of its genetic improvement.

Antimicrobial and Cytotoxic Potential of Eucalyptus Essential Oil-Based Nanoemulsions for Mouthwashes Application.

Objective: An eucalyptus essential oil-based nanoemulsion was produced and evaluated for its antimicrobial properties against Streptococcus mutans and its cytotoxicity in the surface mucous cells of rabbits. Methods: The essential oil-based nanoemulsion was synthesized with two species of eucalyptus-Eucalyptus citriodora and Eucalyptus globulus-followed by physicochemical characterization and the determination of antimicrobial activity and cell viability. Subsequently, the mouthwash formulations (fluoride and fluoride-free) were functionalized with the nanoemulsion, and their in vitro antimicrobial actions were evaluated against S. mutans. Results: The nanoemulsion presented an average particle size of around 100 nm, a polydispersity index close to 0.3, a zeta potential between -19 and -30 mV, a pH close to 7, a spherical shape, and a cell viability above 50%. The antimicrobial activity analysis showed that the nanoemulsion was effective in the control of S. mutans. The mouthwashes functionalized with the nanoemulsion also presented bacteriostatic and bactericidal properties. Conclusions: The bio-based material produced with eucalyptus essential oil presented adequate physicochemical characteristics, with the potential to be used as an innovative material in preventive dentistry, contributing to the maintenance of oral and systemic health.

The Role of trnH-pbsA Spacer Gene in Eucalyptus Species Identification and its Importance in Phylogenetics

The Role of trnH-pbsA Spacer Gene in Eucalyptus Species Identification and its Importance in Phylogenetics

Natural durability of Eucalyptus species harvested as electricity transmission poles in two different ecological zones of Ghana

This study assessed the possibility and feasibility of using two Eucalyptus species for electricity transmission poles in Ghana as a means of minimizing the import of transmission poles in the country. Eucalyptus species are grown in private and government-owned plantations in Ghana due to its growing demand for use as power line transmission poles. The species are seldom used by the furniture industry. The demand from the pole treatment industry for raw materials exceeds the domestic supply of teak, which is commonly used as transmission poles, resulting in the importation of pine poles to cover the deficit, hence the need for this study. The natural durability of Eucalyptus alba and Eucalyptus robusta in the Coastal Savanna Zone (CSZ) and Moist Semi-Deciduous Forest Zone (MSDFZ) was tested using white rot fungus (Coriolopsis polyzona) under an accelerated laboratory test. The results indicated significant variations in the mass lossess be-tween trees in the two vegetation zones. The sapwood and outer heartwood of the E. alba tree species of CSZ recorded the highest mass losses of 41.21 % and 20.79 %, respectively, compared to the E. robusta trees felled from MSDFZ that recorded mass losses of 32.3 % and 5.42 %, respectively. Also, the outer heart- wood and inner heartwood of the E. robusta MSDFZ felled trees were highly resistant (5.42 % and 6.99 %). CSZ wood species were less naturally resistant to C. polyzona attack than those harvested from MSDFZ, which appeared to be less susceptible and more naturally resistant to decay by C. polyzona. Both species are feasible for use as transmission line poles; however, trees from both ecological zones would need chemical preservatives to improve their service life, especially for outdoor applications.

Fire and ant interactions mediated by honeydew and extrafloral nectar in an australian tropical savanna

Fire is a major disturbance affecting ecosystems globally, but its impact on mutualisms has received minimal attention. Here, we use a long-term field experiment to investigate the impact of different fire regimes on globally important ant–honeydew and ant–extrafloral nectar (EFN) mutualistic interactions in an Australian tropical savanna. These interactions provide ants with a key energy source, while their plant and hemipteran hosts receive protection services. We examined ant interactions on species of Eucalyptus (lacking EFNs) and Acacia (with EFNs) in three replicate plots each of burning every 2 and 3 years early in the dry season, burning late in the dry season every 2 years, and unburnt for > 25 years. The proportions of plants with ant–honeydew interactions in Acacia (44.6%) and Eucalyptus (36.3%) were double those of Acacia plants with ant–EFN interactions (18.9%). The most common ants, representing 85% of all interactions, were behaviourally dominant species of Oecophylla, Iridomyrmex and Papyrius. Fire promoted the incidence of ant interactions, especially those involving EFNs on Acacia, which occurred on only 3% of plants in unburnt plots compared with 24% in frequently burnt plots. Fire also promoted the relative incidence of behaviourally dominant ants, which are considered the highest quality mutualists. Contrary to expectations, frequent fire did not result in a switching of behaviourally dominant ant partners from forest-adapted Oecophylla to arid-adapted Iridomyrmex. Our findings that frequent fire increases ant interactions mediated by honeydew and extrafloral nectar, and promotes the quality of ant mutualists, have important implications for protective services provided by ants in highly fire-prone ecosystems.

Nectriaceae species associated to root rot of nursery and young Eucalyptus smithii trees in Uruguay with Ilyonectria charruensis as novel species.

Forestry constitutes an important agronomical activity in Uruguay, involving the cultivation of exotic trees mainly for cellulose pulp production with Eucalyptus species. Over the last decade, E. smithii emerged as a species of interest for cellulose pulping. However, its rapid expansion has coincided with high mortality rates among young trees ranging from 5 to 85%, especially during the first and second summer after plantation. Disease surveys conducted on nine E. smithii commercial fields and three nurseries in southern and eastern Uruguay, yielded a collection of 25 isolates from E. smithii root rot belonging to the Nectriaceae family. In this study, we aimed to identify and characterize these isolates employing phenotypical and molecular studies and to assess their pathogenicity on E. smithii seedlings. Based on morphological features, the Nectriaceae isolates were subdivided into two groups, one resembling Calonectria (n=15) and another Cylindrocarpon-like (n=10). DNA sequences of the partial histone H3 (his3), actine, calmodulin, RNA polymerase II second largest subunit, translation elongation factor 1-alpha (tef1) and β-tubulin (tub2) genes were amplified for Calonectria, as well as partial his3, tef1, tub2 and internal-transcribed spacer and intervening 5.8S (ITS) for the Cylindrocarpon-like group. Based on phylogenetic analysis and phenotypical features three species were identified and characterized; Calonectria pauciramosa (n=15), Dactylonectria novozelandica (n=2), and a novel taxon which we describe here as Ilyonectria charruensis sp. nov. (n=8). The pathogenicity trials revealed that isolates from the three species significantly reduced both shoot and root dry weights of inoculated E. smithii seedlings compared to control plants.