Search Results (445)

Pseudomonas syringae pv. syringae (Pss) is the causal agent of bacterial canker, a disease that can result in yield losses, aerial tissue damage, and tree mortality in stone fruits worldwide. Peach, one of the major stone fruit crops, experiences significant yield losses and tree mortality attributed to bacterial canker in the United States. As the second-largest peach-producing state, South Carolina faces direct and significant impacts due to Pss. Early evaluations of peach scion responses to Pss infection have relied primarily on circumstantial field observations in rootstock trials. Although laboratory evaluations in peach have been reported, these studies primarily focused on pathogen virulence testing or small accession sets and did not establish a standardized, scalable detached twig protocol for systematic germplasm phenotyping. The absence of a clearly described laboratory assay has limited reproducible and large-scale evaluation of bacterial canker tolerance in peach. To address this gap, a detached dormant twig assay, previously developed for cherry, was adapted and optimized for peach. Dormant shoots from nine peach accessions were cut into 10 cm segments, surface-sterilized, and inoculated with a Pss suspension prepared in 10 mM MgCl₂ buffer or with the buffer alone. After six weeks of incubation, inner bark lesion size was evaluated visually and quantified using ImageJ. A newly developed visual rating scale was established and compared with quantitative lesion measurements. Spearman correlation analysis showed strong positive correlations between visual disease scores and ImageJ-based lesion measurements across two independent replicates (ρ = 0.80–1.00, p < 0.01), while shoot segment diameter showed weak-to-moderate negative correlations with disease severity. This adapted and consolidated dormant twig assay provides a practical, reproducible, and scalable method for phenotyping bacterial canker tolerance in peach and supports future germplasm screening and breeding efforts. Full article

Hemipteran plant sap feeders acquire food by inserting their piercing–sucking mouthparts into the apoplast (xylem sap feeders) or symplast (phloem sap feeders). When feeding, these insects seal their stylets inside the plant with a salivary sheath, minimising embolisms. The main impact of the insect on the host or food plant consists of sucking plant sap, transmitting phytopathogenic agents, or triggering galls as hypertrophic and/or hyperplastic neoformations. This paper proposes a rapid method for locating and counting the salivary sheaths of Philaenus spumarius (the Meadow Spittlebug), the primary Italian vector of Xylella fastidiosa, at the feeding point on its host or food plants. Hand-sliced stems of herbs hosting juveniles and olive twigs or leaves feeding the adult spittlebug, preserved while mounted in 75% ethanol (v/v), show the salivary sheaths. Alternative dyeing with acid fuchsin, chlorazol black, or phloroglucinol, and diaphanisation with Essig’s fluid alone or in combination with benzyl alcohol, may help with observations. The 75% EtOH solution provides a better compromise, yielding rapid evidence. The other methods offer similar outcomes but require more time and effort and expose the operator to harmful dyes. Assessing vectors’ access to plants may enable us to quantify the potential number of pathogen transmission events or to spot rejecting clones, thereby advancing the development of robust, effective control strategies that incorporate resistance. Full article

Background/Objectives: The increase in incidences of multidrug resistance exacerbates tuberculosis-related global health challenges and underscores a call for more efforts for development of new antitubercular drugs, including the use of medicinal plants, especially those that have been used for generations by traditional healers. Despite reports of antimicrobial activity and chemical profiling of Kirkia wilmsii (K. wilmsii) extracts, chemical structures of the bioactive agents have not been elucidated. Here, we used a combination of bioactivity-guided fractionation, mass spectrometry, and nuclear magnetic resonance to purify and elucidate the chemical structure of antimycobacterial agents contained in leaf and twig extracts for K. wilmsii. Results: After overnight extraction with acetone and 90 g of dry twigs and leaves produced 5.38 g (6%) and 4.56 g (5%) of product, which displayed moderate antimycobacterial activity of 0.5 and 1 mg/mL, respectively. The antimycobacterial activity was increased six- and three-fold, respectively, after the crude extracts were subjected to solvent–solvent partitioning. Due to many bioactive fractions being obtained after silica gel chromatography purification, fraction 5 of twig extract was prioritized for further purification due to its low minimum inhibitory concentration (MIC) (0.25 mg/mL) and cytotoxicity (20%, in THP-1 cells). Sequential purification of the fraction 5 (twig extract) extracts through the C18 cartridge and high-performance liquid chromatography (HPLC) produced four fractions, which were subjected to structural elucidation. The high-resolution mass spectrometric analyses revealed that the first two eluting peaks had the same mass ion of 441.0822 m/z (M − H⁻), which corresponded to catechin monogallate, and so were the last two eluting peaks, which had a mass ion of 539.0932 m/z (M − H⁻), corresponding to catechin digallate. Further analyses by ¹H, ¹³C, and 2D NMR confirmed the chemical structures of compounds eluting in the first two peaks on HPLC as structural isomers of catechin 3′-monogallate and catechin 4′-monogallate (MIC not determined). Similarly, compounds eluting in the last two peaks were identified as structural isomers catechin 3′-digallate and catechin 4′-digallate, with an MIC of 250 µg/mL against Mycobacterium smegmatis and Mycobacterium tuberculosis H37Rv and an MBC of 500 μg/mL against M. smegmatis. Conclusions: To the best of our knowledge, this study is the first to report the structure of catechin 3′- and 4′-digallate, their antimycobacterial activity, and the existence of acyl migration involving galloyl 3′ and 4′-hydroxyl groups of catechin ring B. Full article

Forest restoration programs are increasingly adopted to mitigate climate change-driven ecosystem degradation, yet the plant functional strategies underpinning successful tree establishment are not fully understood. We investigated the effect of vapour pressure deficit and soil conditions on the interplay between leaf gas exchange and carbon metabolism in three-year-old saplings of different species characterised by distinct functional strategies, as well as non-structural carbohydrate (NSC) partitioning at plant desiccation. We performed two complementary experiments to evaluate interspecific functional differences between Fraxinus ornus L., Quercus cerris L., and Quercus pubescens Willd. in a Mediterranean restored woodland and to compare them with fully irrigated nursery conspecifics. Stomatal sensitivity to closure was similar between species, whereas higher leaf gas exchange and reduced leaf shedding increased twig sugars, as in the case of F. ornus, likely contributing to its better establishment. Irrigation augmented gas exchange rates in potted saplings under moderate evaporative demand but overall did not increase NSCs compared with outplanted conspecifics, possibly because of different carbon demand. Desiccated saplings maintained substantial NSCs, but their reduced pools, especially starch, suggested that they were consumed as a response to drought. Overall, findings indicate that NSC allocation can help define proxies of plant performance in restoration programs. Full article

Willows (genus Salix) are versatile plants with applications in construction, medicine, and biomass fuel in North America. Advances in breeding have improved willow clones for higher yields and pest resistance, but the chemical content and distribution across different plant parts remain poorly understood. This study examined the variation in chemical elements (carbon, hydrogen, nitrogen, sulfur, chlorine, and ash) across six willow clones (India, Jorr, Olof, Otisco, Preble, and Tora) and three tissue types (wood, bark, twigs). We also compared freeze-drying and oven-drying methods to assess their impact on chemical content. Freeze-dried samples generally exhibited higher carbon and hydrogen concentrations than oven-dried samples, with statistically significant differences primarily observed for carbon, while nitrogen showed no overall significant difference between drying methods. Chemical composition varied among clones, although no single clone consistently dominated across all chemical parameters. In contrast, pronounced tissue-type differences were observed: bark had higher nitrogen, carbon, sulfur, chlorine, and ash contents, whereas wood exhibited relatively higher hydrogen concentrations, with twigs showing intermediate values. These findings suggest that accounting for tissue-specific chemical differences can improve the selection and utilization of willow biomass and increase the accuracy of ecological assessments, including carbon storage estimates. The findings of this study indicate that oven-drying should remain in use within the bioenergy sector, whereas freeze-drying ought to become the preferred standard for carbon-accounting protocols. Full article

Rhododendron tomentosum is an aromatic plant belonging to the Ericaceae family, widely used for different applications, but still lacking in its molecular signature. This work provides a complete chemical and biological characterization of the hydroalcoholic extract of R. tomentosum tips of twigs. Combining untargeted metabolomic analysis with bioassays, a correlation between chemical composition and biological activity was defined. To this regard, liquid chromatography high-resolution tandem mass spectrometry (LC-MS/MS) revealed a heterogeneous chemical composition, including flavonoids, such as quercetin, catechin, and their derivatives, as well as a first tentative identification of novel aesculin derivatives. Cell-based model experiments on stressed immortalized human keratinocytes demonstrated the antioxidant activity of the extract. Moreover, it exhibited significant antifungal and antibacterial effects against Trichoderma atroviride AGR2, Botrytis cinerea, and Clavibacter michiganensis, while promoting the growth of the beneficial bacterium Bacillus amyloliquefaciens. These findings highlight the rich diversity of bioactive molecules present in R. tomentosum hydroalcoholic extract, bridging its chemical composition to its functional properties. Overall, these results suggest its promising potential for applications in improving plant health, as well as in pharmaceutical, cosmetic, and agricultural industries. Full article

Understanding the variations in twig and leaf morphologies and photosynthetic physiological characteristics of riparian forest plants in heterogeneous habitats is of great significance for revealing their phenotypic plasticity mechanisms and ecological adaptation strategies. In this study, the riparian forest plant Periploca sepium Bunge was selected as the research object. According to the canopy light environment experienced by the P. sepium population, three habitats were established: under-canopy, gap, and full-sun areas. We studied the twig and leaf morphological and photosynthetic characteristics of P. sepium under heterogeneous light environments, as well as the relationships between these two aspects. Plants in the under-canopy area developed long and thick twigs with few large leaves, coupled with high actual photosynthetic efficiency of photosystem II (Y(II)) and low non-photochemical quenching (NPQ), whereas those in the full-sun area exhibited the opposite covariation strategy. Significant correlations between twig and leaf morphologies and photosynthetic physiological characteristics were found across all habitats. The coordinated variations in twig and leaf morphologies and photosynthetic physiology of P. sepium embody a resource investment trade-off strategy that plants have evolved through long-term adaptation to heterogeneous light environments. Full article

Apple (Malus domestica) is a very important crop grown in Kazakhstan. Cytospora species are capable of causing destructive stem cankers on a wide range of woody plants, including apples, and can lead to twig and branch dieback. This study aimed to identify the Cytospora species responsible for canker disease of apple in Kazakhstan and to assess the susceptibility of major apple cultivars to these pathogens. Investigations were conducted in Almaty, Kazakhstan, during 2023 and 2024. Samples from symptomatic trees were collected, and nine Cytospora isolates were obtained from diseased apple trees. Multigene phylogenetic analysis based on combined sequence data of ITS, tef1-α, tub2, and LSU loci, together with morphological characteristics and pathogenicity assays, revealed two Cytospora species: C. leucostoma and C. sorbicola. The reactions of six apple cultivars (Gala, Golden Delicious, Red Delicious, Granny Smith, Fuji, and Jonaprince) to these species were evaluated, and statistically significant differences were found among cultivars (p < 0.05). The largest lesions occurred on Red Delicious and Fuji, indicating that these cultivars are the most susceptible. In contrast, lesion lengths on Jonaprince were significantly smaller than on all other cultivars, suggesting that Jonaprince is resistant to Cytospora species in Kazakhstan. This is the first report of C. leucostoma and C. sorbicola causing apple canker disease in Kazakhstan. Full article

An increased shift in climate change contributes to accelerated forest dieback around the world. Forest dieback is the process of a forest ecosystem suffering from disease, with mortality rates increasing among trees, potentially leading to the death of the ecosystem. Dieback can be caused through a variety of biotic and abiotic factors such as climate change, land use change, pests, pathogens, and invasive species. Balsam fir trees (Abies balsamea) in eastern North America are particularly vulnerable to dieback. Increased temperatures associated with climate change hinder their tree germination, growth, and competitiveness in an ecosystem. It has been determined that limiting forest dieback damage can be performed by monitoring forest conditions and identifying symptoms such as yellowing of leaves, delayed growth, and reduced stem and twig growth. Diversification was determined to be one of the primary methods of reducing the damage caused by forest dieback. Other methods that were found included decreasing deforestation and limiting the effects of climate change within an ecosystem. These strategies can be applied to balsam fir trees, although the efficacy of mitigation strategies would need to be explored long term. Full article

Melia azedarach L. (Meliaceae) exhibits potential as a source of bioactive antibacterial compounds. In this study, the effect of solvent polarity on ultrasound-assisted extraction of M. azedarach leaves and twigs was evaluated in relation to their phytochemical composition and antibacterial activity against both non-resistant and multidrug-resistant bacteria. The results showed that solvent polarity significantly affected the extraction yield, with methanol and water producing yields above 10%. The methanol extracts of twigs and leaves exhibited the strongest antibacterial activity, showing greater potency against Escherichia coli than Bacillus subtilis. Consistent with these findings, the methanol extracts inhibited the growth of multidrug-resistant enteropathogenic E. coli K1-1, resulting in inhibition zone diameters of 10.93 mm (leaf) and 7.73 mm (twig). Furthermore, the methanol extract contained the highest levels of phenolic, flavonoid, and hydroxyl-rich compounds, which were associated with its antibacterial properties. In silico analysis further revealed that isofucosterol, meliasenin, and melianone exhibited strong predicted binding affinities to key antibacterial proteins, particularly those involved in multidrug-resistant bacterial mechanisms. Full article

The Common European ash (Fraxinus excelsior L.) is one of the main species constituting the field protection forest belts in Northeastern Bulgaria. Studies conducted in shelterbelts in Dobrich and Balchik in July 2020 and in Tutrakan and Dulovo in June–July 2022 revealed severe dieback of ash. The observed symptoms included density thinning of the crowns, dieback of branches, presence of sunken necrotic cankers, and light green to yellow foliage and premature defoliation. Parts of the shelterbelts were completely destroyed with 100% tree mortality. To determine whether the invasive Hymenoscyphus fraxineus or other pathogens are present in the ash field protective forest belts in Northeastern Bulgaria, fungal isolation was undertaken. Samples were collected from four locations: Dobrich and Balchik in June 2020, and Tutrakan and Dulovo in June–July 2022. The morphology, temperature–growth rate relationships, and pathogenicity of the two pathogenic fungal species isolated in this study—Diplodia fraxini and Diplodia seriata—were examined. Morphological and physiological studies confirm the molecular identification of the obtained plant pathogens. The Diplodia fraxini isolates (Dobrich 3, Tutrakan 2, and Dulovo 4) showed mycelial growth between 5 °C and 35 °C, with minimal growth at 5 °C (0.20–0.27 mm/day) and an optimum growth rate of 3.9–4.5 mm/day at 20–25 °C. Growth declined sharply above 30 °C, ceasing entirely at 35 °C. In contrast, D. seriata (Dulovo 5) exhibited higher growth rates, showing limited growth above 5 °C (~1 mm/day), and maximum growth of approximately 8 mm/day at 25 °C. Growth in D. seriata remained moderate up to 35 °C and ceased near 40 °C, indicating a broader temperature tolerance and higher upper thermal limit than D. fraxini. The results from the pathogenicity tests show that D. fraxini can cause necrosis on ash—both on leaves and twigs—and is likely involved in the investigated ash decline cases. Further studies of the spread and epidemiology of D. fraxini are needed in order to establish its occurrence on the territory of Bulgaria. Full article

Branch canker and dieback, caused by Botryosphaeriaceae and Diaporthaceae, is a major disease of walnut (Juglans regia L.) worldwide. In Chile, the impact of pruning wound age and timing on susceptibility to these pathogens in walnut trees remains poorly understood. During June–July (2023) and June–July (2024), this study assessed the effect of pruning wound age of the walnut cv. Chandler on infection by seven fungal species and simultaneously tracked seasonal conidial release of Botryosphaeriaceae spp. in the Maule Region, Chile. Lignified twigs were artificially inoculated at 1, 15, 30, and 45 days after pruning, and necrotic lesion lengths were measured six months post-inoculation. All fungal isolates caused significantly longer lesions than the control (p < 0.0001), with Diplodia mutila, Neofusicoccum nonquaesitum, and N. parvum being the most aggressive. At the same time, Dothiorella sarmentorum and Diaporthe species (Diaporthe australafricana, Di. foeniculina, and Di. patagonica) produced the smallest lesions. Susceptibility decreased with increasing wound age, with a significant interaction between fungal species and pruning wound age. Spore trapping of Botryosphaeriaceae revealed that dispersal was positively associated with rainfall (r = 0.81, p < 0.0001), relative humidity (r = 0.51 to 0.61, p < 0.05) and average temperature (r = 0.32 to 0.58, p < 0.05), but negatively or not significantly correlated with maximum temperature (r = −0.59 to −0.79, p > 0.05). These results demonstrate that rainfall or relative humidity, moderate conditions, and favor conidial release. At the same time, infection risk declines with wound age, underscoring the need to adjust pruning schedules and preventive strategies to reduce disease risk in walnut orchards. Full article

Accurate identification of deciduous woody species in winter is challenging, and the misidentification can lead to ecological and management damage. This study aims to substantiate a diagnostic system for woody species based on macromorphological bark characters. First, we reviewed the literature on bark-based species identification to assess existing approaches and their limitations. Building on this, we identified informative macromorphological features of bark through both literature analysis and our experiences. These characters cover all developmental phases, including twigs, young bark, and mature bark, and are supported by new diagnostic terminology. Using this framework, we compiled a character set for 115 Central European woody taxa, providing practical, primarily qualitative traits that can be applied directly in the field. Finally, we developed and tested “Single-access Keys” as an alternative to conventional dichotomous keys, demonstrating their effectiveness in enabling flexible and rapid species recognition, even under atypical conditions or when only partial observations are possible. Our results highlight the value of bark macromorphology as a diagnostic tool and emphasize its potential for advancing thematic identification keys, as well as digital applications in forestry, taxonomy, and ecological monitoring. Full article

The growing worldwide demand for essential oils (EOs) brings new opportunities for Azorean Cryptomeria japonica aerial parts waste valorization. Therefore, the phytochemical and bioactivity investigation of EOs from different Azorean C. japonica tissues, such as twigs (Az–CJT), remains imperative to add more value to C. japonica’s EO industry, alongside the contribution to the local sustainable circular bioeconomy. This study provides, for the first time, GC–MS analysis and brine shrimp toxicity of the EO hydrodistilled from Az–CJT and aims to compare these parameters with those determined for a commercial Azorean C. japonica (branches and foliage) EO obtained through steam distillation. The main Az–CJT EO components were α-eudesmol (19.53%), phyllocladene (14.80%), elemol (12.43%), nezukol (11.34%), and γ-eudesmol (5.32%), while α-pinene (28.62%), sabinene (24.30%), phyllocladene (5.10%), β-myrcene (5.09%), and limonene (4.93%) dominated in the commercial EO. Thus, Az–CJT EO exhibited the highest sesquiterpenoids (43.52%), diterpenes (20.85%), and diterpenoids (13.21%) content, while the commercial EO was dominated by monoterpenes (74.61%). The Az–CJT EO displayed significantly higher toxicity than the commercial EO, with mortality rates of 87.7% and 16.9%, respectively, at 100 µg/mL. This result is likely related to the substantially higher terpenoid content of Az–CJT EO (61.20% vs. 9.44%), largely attributed to the sesquiterpenoid fraction. Due to its distinct chemical profile, Az–CJT EO may have differential commercial applications, warranting further investigation into its bioactive value and safe use. In conclusion, this study adds knowledge on the potentialities of C. japonica aerial parts’ EOs from the Azorean region. Full article

Pachysandra terminalis (P. terminalis), a plant belonging to the Buxaceae family, is known as a great source of aminosteroid alkaloids. In a previous communication, we reported on the isolation of a variety of aminosteroids from P. terminalis, which presented interesting activity against the protozoan pathogens, Trypanosoma brucei rhodesiense and Plasmodium falciparum. In the present study, variations in the alkaloid profile of P. terminalis related to seasonal changes as well as differences between plant organs (leaves and twigs) and between plant populations were investigated to prioritize candidates for targeted isolation in further studies. For this purpose, sample material of P. terminalis was collected from the two nearby populations in monthly intervals over one year. The ethanolic (75%) extracts were analyzed using UHPLC/+ESI-QqTOF-MS/MS, and the resulting data converted to variables encoding the intensity of MS signals in particular m/z and retention time (t_R) intervals over the chromatographic runs. The very large and complex data matrix of these <t_R:m/z> variables was evaluated using multivariate data analysis, especially principal component analysis (PCA) and volcano plot analysis of t-test data. The results of these analyses, for the first time, allowed a holistic analysis of variation in the alkaloid profiles in P. terminalis organs over the vegetation period. The evaluation of the PCA scores and loadings plots of principal components 1 through 3, as well as of volcano plots, highlighted 25 different compounds, mostly identified as aminosteroid alkaloids, that were most relevant for the differences between leaves and twigs and between the two populations and mainly determined the changes in their chemical profiles over the vegetation period. Full article