Forest Pathology最新文献

The aim of this study was to confirm the presence of bacteria that are partly responsible for the oak dieback phenomenon, known as Acute Oak Decline, in Serbia. Seventeen symptomatic oak trees (both Quercus robur and Quercus cerris) were sampled in April 2024 and analysed using multiplex real-time PCR. Brenneria goodwinii was detected in one tree from Morović, whereas Gibbsiella quercinecans was found in two trees from Morović and Progar. This is the first report of these bacteria in Serbia, despite bioclimatic models predicting a low likelihood of their presence in the Balkans. Our results indicate the presence of oak dieback bacteria in areas where they have not yet been reported, highlighting the need for increased research and awareness of bacterial diseases in forest trees.

The occurrence of Oomycetous pathogens and their pathogenicities on chestnut saplings, grown at four nurseries were investigated in this study. Also, the effectiveness of foliage applications of phosphorous acid (H₃PO₃) and Potassium phosphonate (K₃PO₄), against Phytophthora cinnamomi which is the most common root rot pathogen of chestnuts in Türkiye was evaluated. Forty-three Oomycetous isolates were obtained using selective media, from sixty plant and twenty soil samples collected from the nurseries. Oomycetous pathogens were identified by molecular tools, using ITS, cox1 for Phytophthora spp. and ITS and coxII primers for Phytopythium spp. Phytophthora cinnamomi was the most frequently isolated species, recovered from two nurseries, Gökçebey and Pınar, while Phytophthora inundata was from only the Pınar nursery. Two Phytopythium species, Phytopythium litorale and Phytopythium vexans were also frequently isolated, the former from Pınar and Hendek nurseries and the latter from Gölköy, Hendek and Gökçebey nurseries. Phytopythium spp. did not produced necrosis as large as P. cinnamomi when inoculated on to young saplings. When H₃PO₃ and K₃PO₄ were applied on to foliage one or 2 weeks before the pathogen inoculation, they reduced necrosis lengths significantly compared to the simultaneous application of H₃PO₃ and K₃PO₄ with the pathogen inoculations. Necrosis lengths obtained by the K₃PO₄ treatment were significantly lower than H₃PO₃ treatment.

During the summer of 2019, spots were detected on the leaves of black olive (Bucida buceras L.) trees distributed in urban areas in Los Mochis, Sinaloa, Mexico. Two single-spore isolates were obtained and identified as Colletotrichum siamense by phylogenetic analyses of concatenated sequences of the ITS, gapdh, tub2, act, chs-1 and gs genes. The pathogenicity of the isolates was demonstrated through inoculations under controlled conditions. This is the first report of C. siamense causing leaf spot of black olive in Mexico and worldwide.

Erysiphe species infecting oaks in North America are common and widespread, but compared to Asia and Europe, the taxonomy and phylogeny of North American species is unknown. The present study addresses this dispairity. Comprehensive multilocus phylogenetic analyses, including CAM, GAPDH, GS, ITS, RPB2 and TUB, revealed a high degree of co-evolution between North American oaks and the Erysiphe spp. that infect them. A concatenated multilocus tree and individual trees based on single loci revealed many highly supported species clades. The clades are formally named to conform with the current taxonomic classification. Available names, such as E. abbreviata, E. calocladophora and E. extensa, are associated with corresponding clades, and are newly circumscribed supported by ex-type sequences or, if not available, by the designation of epitypes with ex-epitype sequences. Erysiphe densissima is reintroduced for a clade that corresponds to the old name ‘E. extensa var. curta’. Eight new species are described, including Erysiphe carolinensis, E. gambelii, E. occidentalis, E. phellos, E. pseudoextensa, E. quercophila, E. quercus-laurifoliae and E. schweinitziana. A new diagnostically and taxonomically relevant trait associated with the anamorphs of North American Erysiphe species on oaks has been assssed. This is a special conidiophore-like lateral outgrowth of the superficial hyphae, comparable to ‘aerial hyphae,’ which are also known for species of the powdery mildew genus Cystotheca which also infect Quercus species.

Scotch broom (Cytisus scoparius) and French broom (Genista monspessulana) are two woody legumes native to Europe and North Africa that have become invasive in different countries around the world. In Chile, they are among the most serious invasive plants of the central southern regions, where they cause severe negative impacts to natural environments, and have become a serious problem in plantation forestry. Numerous studies have sought biological control agents for both species, however, this approach has not been explored in Chile. The aim of this study was to prospect for pathogens and diseases occurring in these weeds in invaded areas of Chile and explore these as potential biocontrol agents. Surveys were conducted in 13 invaded areas between the Biobio and Araucanía regions, and diseased plants of both species were collected for isolation. The putative pathogens isolated from each broom species were inoculated into healthy plants, and isolates producing symptoms identified by DNA sequencing. These isolates were used in pathogenicity tests on both weed species and on Pinus radiata and Eucalyptus globulus plants. The most aggressive pathogens were Fusarium sambucinum, F. solani and Phytophthora multivora on C. scoparius; Neofusicoccum parvum and Chondrostereum purpureum on both weeds, and F. tricinctum s.l. on G. monspessulana. Except for F. trincinctum s.l., all isolates caused lesions on both weeds, and except for P. multivora, all isolates caused lesions on E. globulus and/or P. radiata. Most pathogens on C. scoparius had been reported previously on this host elsewhere, while most pathogens on G. monspessulana represent novel associations.

Fine structures were investigated on Pinus thunbergii needles in the coastal area of Seocheon, Korea. Both asymptomatic and necrotised needles were collected and subjected to electron microscopy and X-ray microanalysis. Particles of varying sizes and shapes covered both the asymptomatic and necrotised needles. The ratio of clogged stomata to open stomata was significantly higher in necrotised needles. X-ray microanalysis revealed particles composed of aluminium, calcium and silicon. However, sodium chloride crystals were rarely observed. These results suggest that needle necrosis in pine species may be associated with stomatal clogging by aerosol particles.

Bacterial tree diseases have been mainly studied in agriculture and horticulture. For forest trees, damage due to bacterial diseases is understudied. Moreover, bacterial tree diseases often appear in the context of so-called complex diseases, which are dependent on other factors, such as multiple microorganisms, insects or abiotic factors which weaken the host. In recent years, outbreaks of bacterial tree diseases, such as Xylella fastidiosa in the Mediterranean region or acute oak decline (AOD) in the United Kingdom, raised the awareness of bacterial diseases on forest trees. In this review, we aim to summarise the current issues and available knowledge about bacterial diseases of forest trees in Central Europe. Furthermore, we identify potential bacterial pathogens that could gain importance in the future for central European forests. The methods used were a systematic literature search and the analysis of the data collected over the last 10 years on bacterial diseases by the Swiss forest protection service. We conclude that, on one side, complex bacterial diseases could increase in importance, especially considering ongoing climate change. Therefore, the bacterial community of diseased trees (the pathobiome) needs to be studied more in depth to understand the emergence of complex bacterial diseases. On the other side, host ranges of highly pathogenic invasive genera and species, such as Xylella, need to be investigated experimentally for common central European tree species and varieties, to implement proactive risk management strategies against bacterial diseases in forest trees. Finally, urban trees and green spaces should be monitored more closely, as they could serve as starting points for bacterial disease outbreaks in forests, similarly to other emerging diseases and pathogens.

This study investigated the severity of mistletoe infection on junipers and the relationship between tree characteristics, physiographic factors and mistletoe infection. The study was conducted in two protected areas: Parvar and Miankouh Tash in Semnan Province, Iran. A dwarf mistletoe-infested area of 400 ha was sampled by placing a 250 × 250 m grid over a map of each study area. A 20 × 20 m (400 m²) plot was placed at the intersection of grid lines. This resulted in a total of 110 forested plots: 45 plots in Parvar and 65 plots in Miankouh Tash. In each plot, all live junipers were measured for total height, crown area, collar diameter and crown diameter. Mistletoe severity was estimated using the 6-class dwarf mistletoe rating system (DMR). Dead trees were also recorded and examined for evidence of past mistletoe infection. The Boruta algorithm was used for feature selection, and the selected features were utilised for predicting DMR using a random forest (RF) model. Over 40% of junipers in the sample plots were infected and 7.5% were dead. Mortality was greater in severely infested plots compared to uninfested and lightly infested plots. The results of univariate analysis demonstrated that the largest trees across plots were more severely infected. Infection severity was highest on steep terrains (slopes more than 60%) where the largest junipers were growing. Based on Boruta feature selection algorithm, collar diameter, tree height and crown area of junipers have been detected as the most important variables for the explanation of infection severity. Crown diameter, geographical aspect, density of juniper trees, altitude and juniper canopy cover were classified as tentative variables in this model. Slope percentage beside two variables related to stand characteristics including all woody species (basal area and tree density) were the rejected variables. The correlation coefficient (r) and root mean square error (RMSE) between the predictions by RF and the measured DMR were 0.83 and 0.53 respectively. These results indicate that the selected environmental variables can be used for spatial prediction of DMR in both study areas. Because increased mortality was observed for severely infected areas, more efficient management methods are needed to control the dwarf mistletoe populations in the Alborz Mountains.