Search Results (152)

Myrtaceae is one of the largest families of flowering plants and is well known for its prolific terpene production. To investigate the genetic basis underlying this high-level terpene output, we conducted comparative genomic analyses of genes of the entire terpene biosynthetic pathways in selected Myrtaceae species and representative species from three other families within the order Myrtales. Our analyses revealed that genes encoding enzymes in the upstream terpene biosynthetic pathways are generally conserved in copy number across Myrtales. Similarly, isoprenyl diphosphate synthases, which are positioned centrally and responsible for producing the direct precursors of major terpene classes, also exhibit conserved gene numbers among these species. In contrast, substantial differences were observed in the number of terpene synthase (TPS) genes, which function downstream and directly catalyze terpene formation. Myrtaceae species possess markedly more TPS genes than species from other Myrtales families. This expansion is primarily attributable to increased gene numbers in the TPS-a, TPS-b, TPS-g, and TPS-e/f subfamilies, with the first three subfamilies largely associated with sesquiterpene and monoterpene biosynthesis. Further analyses indicate that the enlarged TPS-a and TPS-g subfamilies resulted at the origination of Myrtaceae-specific groups, whereas TPS-b exhibited Myrtaceae-specific expansion. In Eucalyptus grandis, tandem duplication makes a larger contribution to the expansion of TPS-a, TPS-b and TPS-g subfamilies than interchromosomal duplication. The majority of these TPS genes exhibit moderate to high levels of expression in leaves, consistent with their role in elevated terpene production in leaves of E. grandis. Collectively, our findings are consistent with the hypothesis that the novel terpene-producing capacity of Myrtaceae is driven primarily by Myrtaceae-specific origination and/or expansion of downstream TPS genes rather than changes in upstream pathway gene copy numbers. Full article

Eucalyptus spp. are the most important timber and pulpwood species in southern China. This tree species is frequently and severely damaged by the leaf-eating pest Buzura suppressaria, which significantly impairs photosynthesis and hinders the healthy and sustainable development of the Eucalyptus industry. To investigate the defensive responses of Eucalyptus urophylla × Eucalyptus grandis to pest (B. suppressaria)-feeding and leaf-clipping stress, this study measured the temporal changes in defense enzyme activities and defense compounds in Eucalyptus under conditions of pest-feeding and leaf-clipping stresses, aiming to provide a theoretical basis for resistance breeding in Eucalyptus. The results show that pest-feeding and leaf-clipping stress groups significantly affected the peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) activities in Eucalyptus leaves. Within a short period after stress (3 h), POD activity was significantly reached 444.83 U by leaf-clipping stress, whereas it was significantly inhibited (34.83 U) by pest-feeding stress. PPO activity was significantly enhanced to 95.25 U under pest-feeding stress within 3 h, while leaf clipping induced a lower level of PPO activity (58.75 U). PAL activity was significantly induced to 474.38 U by leaf-clipping stress at 3 h, whereas pest-feeding stress resulted in a moderate increase to 238.00 U. Both pest-feeding and leaf-clipping stresses had significant effects on the contents of defense compounds in Eucalyptus leaves. Within a short period (3 h), both leaf-clipping and pest-feeding stresses significantly induced the accumulation of salicylic acid (0.226 μg/g and 0.326 μg/g, respectively), jasmonic acid (0.239 μg/g and 0.278 μg/g, respectively), and tannin (0.581 μg/g and 0.657 μg/g, respectively). The POD activity and salicylic acid content were identified as the primary factors in Eucalyptus responses to pest-feeding and leaf-clipping stresses. In conclusion, biotic (pest-feeding) and abiotic (leaf-clipping) stresses can induce higher activities of related defense enzymes while also promoting the synthesis of greater quantities of defensive chemical compounds, thereby enhancing the resilience to biotic and abiotic stresses in Eucalyptus. This study provides important practical guidance for insect-resistant Eucalyptus breeding and implementing integrated pest management strategies. Full article

Eucalyptus is a highly diverse genus of the Myrtaceae family that is planted worldwide. Many changes occur during callus development, an important process during in vitro plant regeneration. In this study, we conducted methylome and transcriptome analyses to reveal such changes. The results showed that differentially expressed genes between E. camaldulensis (voucher ID: c0009; high embryogenic potential) and E. grandis × urophylla (voucher ID: j0017; low embryogenic potential) during callus development were enriched in plant hormone signal transduction and MAPK (Mitogen-activated protein kinase) signaling pathways. qRT-PCR analysis showed AHP, BAK1, BSK, CRE1, GID1, MKS1, PR-1, PYL, RbohD, and TCH4 could be involved in the callus development and plantlet regeneration capacity. The differences observed in regenerative potential during callus maturation between the two species under study provide a reliable molecular basis for the study of Eucalyptus regeneration mechanisms. Full article

Persistent cloud cover and frequent rainfall in subtropical regions throughout the year significantly limit the applicability of optical remote sensing for tree species identification, thereby constraining dynamic forest monitoring and precise management of forest resources. To address this challenge, this study proposes a tree species identification method that integrates multi-source remote sensing temporal features. By combining multi-temporal optical imagery from Sentinel-2 and dual-polarisation Synthetic Aperture Radar (SAR) data from Sentinel-1, we constructed a comprehensive feature set that incorporates spectral, structural, and phenological attributes, including various vegetation indices, backscatter coefficients, and polarimetric decomposition parameters. Through correlation analysis and assessment of temporal feature variability, five distinct integration strategies (T1-T5) were developed to classify six typical subtropical tree species: Pinus massoniana, Pinus elliottii, Acacia, Eucalyptus grandis, Mangrove, and Other hardwoods, using a random forest classifier. The results indicate that the multi-source feature fusion approach significantly outperforms single-source models, with the T5 strategy achieving the highest overall accuracy (OA) of 95.33% and a Kappa coefficient of 0.94. The red-edge vegetation indices and SAR polarimetric features were identified as major contributors to improving the classification accuracy of hardwood species. This study demonstrates that multi-source remote sensing data fusion can effectively mitigate the spatiotemporal constraints of optical imagery, providing a viable solution and technical framework for high-accuracy remote sensing classification in complex subtropical forest environments. Full article

Eucalyptus leaf blight is a globally distributed disease caused by Calonectria fungi, with C. pseudoreteaudii being the dominant pathogen in Fujian, China. The crude toxin produced by C. pseudoreteaudii is a key virulent factor. To investigate the resistance mechanism triggered by crude toxin infection, transcriptome sequencing, physiological observations, and qRT-PCR analyses were conducted. Transcriptome analysis of Arabidopsis thaliana treated with C. pseudoreteaudii crude toxin revealed that a flavin-containing monooxygenase 1 gene (AtFMO1) exhibited the highest differential expression with DMSO control. Compared with Arabidopsis ecotype Col-4 (the wild type, WT), AtFMO1 knockout mutant (Δfmo1) plants displayed dose-dependent leaf margin yellowing accompanied by reduced callose deposition and hydrogen peroxide (H₂O₂) accumulation under crude toxin treatment. qRT-PCR analysis of key genes from two immune pathways showed that the salicylic acid-dependent (SA-dependent) pathway was likely Arabidopsis’s primary response pathway for crude toxin. In E. grandis, a total of 38 EgFMOs were identified, with eight EgFMO1s, based on the protein sequence similarity, conserved domain, and motif pattern. qRT-PCR analysis of EgFMO1s revealed two major expression patterns in response to crude toxin treatment: an initial downregulation followed by upregulation, and continuous upregulation. Collectively, these results suggest FMO1 plays a positive role in resistance to C. pseudoreteaudii crude toxin in both A. thaliana and E. grandis. Full article

Cortical microtubules comprise heterodimeric units of α- and β-tubulin which have been shown to guide the deposition of cellulose microfibrils in plant cell walls where their arrangement is important in determining cell morphology and cell wall properties. Tubulin genes are highly expressed in woody tissues and a functional study has demonstrated a role for a β-tubulin gene family member in affecting the orientation of cellulose microfibrils in wood fibre cells, an important trait in determining the mechanical properties of wood fibres. To further understand the role of tubulins in plant cell trait determination, this study identified and investigated the expression of the α- and β-tubulin gene families in Eucalyptus and then, using transgenesis techniques, investigated the role of specific eucalypt tubulin isoforms in determining secondary cell wall traits of wood fibres in plant stems. This study found that the α- and β-tubulin gene families in Eucalyptus are relatively small compared to other species and show higher expression in woody stem tissue when compared to leaf. Functional studies revealed that cambial cells transformed with α- and β-tubulin overexpression and knockdown vectors, either on their own or in combination, lead to changes in the angle of microfibrils in the secondary cell wall of wood fibre cells with Class I- and Class I-like gene family members explicitly involved. This study demonstrates the importance of tubulins in determining the mechanical properties of wood fibres through a mechanism involving specific tubulin isoform expression during wood fibre formation. Full article

Monitoring spatiotemporal dynamics of aboveground carbon (AGC) storage at the tree species level is crucial for evaluating the ecological impacts of large-scale infrastructure projects and facilitating accurate ecological environmental management. However, existing studies heavily rely on interannual coarse-spatial-resolution forest-type products, leading to significant uncertainties in carbon estimation, particularly in fragmented linear engineering zones. This study integrated Sentinel-1/2 data with a random forest (RF) model to map tree species distribution (overall accuracy = 85.18%; Kappa = 0.8319) and AGC estimation (R² = 0.7057; RMSE = 13.35 Mg ha⁻¹) at a 10 m resolution in the Pinglu Canal Basin from 2019 to 2024. The results revealed a total AGC decline of 16.88% across the watershed. Spatially, the Environmental Impact Area (EIA) functioned as the primary disturbance core (experiencing a 28.91% loss), while the Ecological Buffer Area (EBA) acted as a regional carbon stabilizer. At the species level, while Eucalyptus grandis accounted for the majority of carbon depletion, Pinus massoniana exhibited a resilience-driven rebound in the mid-construction phase. Meanwhile, Litchi chinensis and other native species demonstrated steady gains. Cumulatively, these species-specific carbon gains associated with natural growth and restoration initiatives effectively offset 34.45% of the carbon loss. These findings provide quantitative evidence supporting the potential of green engineering to mitigate the ecological footprint of infrastructure development. This study offers a robust monitoring tool for low-carbon infrastructure and directly supports the United Nations Sustainable Development Goal 15 (SDG 15) related to forest conservation and ecological restoration. Full article

Beauveria bassiana can colonize plants, acting against insect pests and promoting plant growth. This study evaluated how different fungal inoculation methods affected Eucalyptus grandis growth and the foraging behavior of ants. An isolate (LPP 139) was identified as B. bassiana based on ITS sequences. Seedlings were submitted to three inoculation methods using fungal suspensions at 1 × 10⁸ conidia mL⁻¹: (1) soil drenching at sowing (SD), (2) soil drenching 20 days after sowing (20SD), and (3) foliar spraying 20 days after sowing (20F) when compared to controls. SD treatment enhanced plant height (mean 25 cm with a 31.6% increase compared to the controls; p = 0.0353) and shoot fresh weight (mean 1.5 g, a 50% increase; p = 0.0154), while 20SD increased leaf number (141.4% increase; p = 0.0419). The 20F treatment increased leaf number (287.9% compared to the controls; p = 0.0006), shoot weight (mean fresh weight 1.5 g, a 50% increase; p = 0.0213 and mean dry weight 0.7 g, a 75% increase; p = 0.0236), and reduced leaf-cutting ant foraging (mean 26 cm², a reduction of 53.6%; p = 0.0134). These findings highlight the dual action of B. bassiana, promoting plant growth and reducing the activity of ants. Full article

Eucalypt plantations form the basis of Brazilian forestry; however, successive rotations under coppice systems often experience productivity declines. This study presents an original long-term investigation over a 13-year cultivation cycle (2005–2018) with Eucalyptus grandis W. Hill ex Maiden × E. urophylla S. T. Blake, assessing whether the full maintenance of nine phosphate fertilization packages could sustain productivity from the first to the second rotation in a commercial plantation in Itamarandiba, Minas Gerais. Continuous forest inventories and rotation-specific growth modeling were used. Productivity in the second rotation declined by 33%–46% in packages TP1 to TP6, which included various phosphorus sources, highlighting the recurring challenges of coppice systems. Conversely, the highest and most consistent yields (~305 m³ ha⁻¹ rotation⁻¹) were obtained with package TP9, which consisted of 280 kg ha⁻¹ of triple superphosphate (TSP) applied at the beginning of each rotation and 600 kg ha⁻¹ of ammonium sulfate (SA) in split topdressing applications. These findings demonstrate that the full maintenance of fertilization, specifically with highly soluble phosphorus sources combined with balanced nitrogen and sulfur supplementation, is an effective strategy to secure productivity and ensure the economic viability of coppice systems. This offers a new paradigm for managing successive rotations, where nutritional synergy, rather than single-nutrient fertilization, is key to enhancing the resilience of clonal eucalypt plantations. Full article

Background: Recently, the use of volatile compounds as spatial repellents have received special attention as a promising strategy for adult An. gambiae s.l control. Anopheles gambiae s.l is a primary vector of malaria, an arthropod-borne disease of global significance. Current strategies for controlling mosquitoes heavily rely on vector control methods. Understanding the responses of these vectors to volatile compounds will be helpful in the formulation of repellants or attractants for control vector populations. This study was conducted in Nwoya district, Uganda, one of the high-malaria-transmission areas in the northern part of Uganda, as one of the ways of reducing contact between the parasite, vector, and malaria outbreak. Materials and Methods: In this study, a laboratory-reared female An. gambiae Kisumu strain from Uganda Virus Research Institute (UVRI) insectaries were used to examine spatial behavior responses of An. gambiae to selected EOs of Eucalyptus grandis and Cymbopogon citratus. Spatial activity responses were measured using a Y-tube olfactometer under controlled conditions using three replicates in various concentrations of the tested EOs. These oils were extracted by steam distillation and the main constituents identified using gas chromatography–mass spectrometry. Results: Mosquito response curves indicating effective repellency concentrations are reported, as well as the gas chromatography–mass spectrophotometry analysis results. For Eucalyptus grandis, the two components with the highest composition were L-α terpineol and Eucalyptol, while those for Cymbopogon citratus were Lavandulol, methyl ether, and citral. Other components had a percentage composition less than five but they might play a big role in repellent activity against mosquito species. Conclusions: The mosquito repellency results in this study indicate that Eucalyptus grandis and Cymbopogon citratus EOs could be used as mosquito repellents, providing more evidence that natural products have promising lead compounds for further development of botanical spatial repellents. Further characterization of EOs and testing on mosquito behavior related to the prevention of malaria and other vector-borne diseases will promote innovation in vector control and provide new vector control tools that are needed in this era of insecticide resistance. Full article

This study evaluated the physiological and biochemical responses of three Eucalyptus genotypes (E. urophylla; hybrid E. urophylla × E. grandis; hybrid E. urophylla × E. camaldulensis) under three water regimes (well-watered—plants watered daily with 70% of field capacity; rehydrated—water supply suspended at initial wilting symptoms; water deficit—water supply suspended upon reaching 50% of soil water retention capacity) in a warm tropical environment. The treatment was performed through daily weighing of plant pots and addition of the required water amount to reach the pot weight in each treatment. Measurements included stomatal conductance (gs), carbon assimilation rate (A), transpiration rate (E), leaf water potential (Ψ_leaf), chlorophyll content (a and b), proline accumulation, and the activities of superoxide dismutase (SOD) and catalase (CAT). The genotypes exhibited contrasting drought responses: E. urophylla × E. camaldulensis showed the highest resilience, maintaining gas exchange, water status, and proline accumulation under stress. E. urophylla × E. grandis displayed intermediate tolerance, while E. urophylla was the most sensitive. Overall, drought tolerance in Eucalyptus emerged from the coordinated interaction of hydraulic, osmotic, and antioxidant mechanisms. Full article

Eucalyptus plantation forests play an important role in the global trade balance, and have been challenged with the Eucalypt Physiological Disorder (EPD) exhibiting symptoms on barks. Despite of that, there is little information on the anatomical features of phloem and periderm associated with this disorder. Although tolerant and susceptible commercial clones exhibited similar anatomical structures, they differed in the proportions of conducting and total phloem tissue and the amount of phloem containing Calcium oxalate (CaOx) crystals. The frequency and diameter of sieve tube elements (STEs) also varied among the tested clones. The increased area of phloem with non-collapsed STE and CaOx crystals were linked to the EPD tolerant phenotype. Bark, secondary phloem, and periderm thickness were correlated with EPD scores. Structural characteristics of phloem cells is correlated with increasing stem diameter. Bark and phloem thickness exhibited significant and positive associations with EPD-tolerant clones and stem diameter, while negative correlations with EPD scores. These connections corroborate the positive impact of increasing the proportion of total phloem thickness on stem diameter growth and EPD tolerance. The present results were based on restricted, yet commercially important, Eucalyptus species (E. grandis, E. urophylla and E. grandis × E. urophylla hybrids) highlighting bark and phloem traits linked to plant growth and EPD tolerance. Full article

Soil organic carbon (SOC) is a critical component of the soil carbon pool, significantly influencing soil fertility and forest ecosystem productivity. Eucalyptus grandis (Rose Gum), one of the most widely introduced and economically valuable fast-growing tree species worldwide, plays an indispensable role in pulpwood production, construction, and bioenergy, and is commonly established and managed in successive rotations in operational practice. Despite its importance, the effects of successive planting on SOC and its labile fractions in plantation soils remain poorly understood. In May 2017, a space-for-time substitution approach was employed to study the effects of successive planting of E. grandis plantations on SOC and its labile fractions, including dissolved organic carbon, light-fraction organic carbon, particulate organic carbon, microbial biomass carbon, and readily oxidizable carbon. The results indicated that the content of SOC and labile organic carbon (LOC) fractions declined concomitant with an increase in successive planting generations. Specifically, total SOC content significantly decreased from 12.63 g·kg⁻¹ in the first-generation forest to 9.37 g·kg⁻¹ in the third-generation forest. The contents of LOC fractions also showed a significant decrease from the first to the second generation, but the rate of this decline slowed in the third generation. The soil carbon pool management index (CPMI) decreased significantly from 100 in the control forest to 46.64 in the third-generation plantation. Redundancy analysis identified water-soluble nitrogen and total nitrogen as the principal common factors exerting influence over SOC and its labile fractions in E. grandis plantations. These findings indicate that successive planting of E. grandis in artificial forests primarily reduces SOC and LOC fractions by lowering soil nutrient content, leading to a decline in soil carbon pool quality. The findings of this study may help provide a scientific basis for the sustainable development of E. grandis plantations in this region. Full article

Soil microorganisms are important decomposers in soil, and they play important roles in litter degradation, nutrient cycle and balance, soil physicochemical property improvement, and soil fertility maintenance. To understand the influence of Eucalyptus plantations on the growth, reproduction, and activity of soil microorganisms in severely degraded land, the Leizhou Peninsula in tropical China was selected as the research area. The vegetation restoration types of Eucalyptus urophylla × grandis planted in its severely degraded red soil areas (ES: Eucalyptus–shrub, EG: Eucalyptus–grass, and ED: Eucalyptus–Dicranopteris pedata (Houtt.) Nakaike) were studied, and the nearby natural vegetation types (S: shrub, G: grass, and D: Dicranopteris pedata) served as control groups. The microbial characteristics of different vegetation restoration types were compared, and the influence of Eucalyptus plantations on the growth, reproduction, and activity of soil microorganisms in severely degraded red soil areas was discussed by setting up sample plots for investigation, sample determination, and statistical analysis. The structure of soil microorganisms differed significantly between Eucalyptus vegetation restoration (ER) and natural vegetation restoration without Eucalyptus (NER). Key organic decomposers, including bacterial genera such as Candidatus Solibacter (ER: 1.2 ± 0.4% vs. NER: 0.9 ± 0.1%), Candidatus Koribacter (ER: 1.0 ± 0.4% vs. NER: 0.7 ± 0.1%), and Edaphobacter (ER: 0.9 ± 0.1% vs. NER: 0.4 ± 0.1%), as well as fungal genera such as Rhizophagus (ER: 0.1 ± 0.0% vs. NER: 0.0 ± 0.0%), Paxillus (ER: 0.1 ± 0.0% vs. NER: 0.0 ± 0.0%), and Pisolithus (ER: 0.1 ± 0.0% vs. NER: 0.0 ± 0.0%), exhibited a significantly higher relative richness and a broader distribution in ER compared to NER (p < 0.05). Soil microbial biomass carbon, nitrogen and phosphorus (MBC, MBN, MBP), community structure (keystone taxa and symbiosis network complexity), and functional genes (for growth, reproduction, and decomposition) in ER, especially in ES, were significantly higher than in NER. This study illustrated that Eucalyptus plantations, especially ES types, can promote the growth and reproduction of soil organic decomposers, improve microbial metabolic and biological activities, and increase functional diversity and interactions among microorganisms, thus accelerating the cycle of soil carbon, nitrogen, and phosphorus nutrients, improving soil quality and fertility, and accelerating the recovery of degraded soil fertility. In areas with serious soil degradation and where natural vegetation restoration is difficult, planting Eucalyptus, especially while guiding the understory vegetation to develop into the shrub vegetation type, is an effective vegetation restoration model. Full article

This study aimed to evaluate the adhesion behavior of wood from an E. urophylla × E. grandis clone using the application of melamine–urea–formaldehyde (MUF), resorcinol–formaldehyde (RF), and polyurethane (PUR) adhesives in test samples obtained from 12 glulam beams. Adhesives were characterized by their pH, viscosity, density, and solid content. The wood–adhesive interface was assessed through the shear strength, percentage of wood failure, delamination, and photomicrograph analysis. A microdensitometer with X-rays and a resistograph were used to determine the material density and drilling resistance of the elements. Adhesive pH values ranged from 6.35 to 9.05. MUF exhibited the highest viscosity (1169 cP), while the adhesive density varied between 1.29 and 1.67 g cm⁻³. No statistically significant difference in results was obtained for the shear strength in dry conditions. The MUF adhesive showed a lower percentage of wood failure compared to PUR and RF. In the delamination test, the wood beams glued with RF yielded the best results. Photomicrographs revealed the adhesive’s penetration into the wood’s anatomical structure. Densitometry and resistograph profiles accurately represented the beam balancing configuration. The adhesives PUR, RF, and MUF demonstrated suitability for producing glulam beams with the Eucalyptus clone wood evaluated in this study. Full article