Search Results (19)

Common buckthorn (Rhamnus cathartica L.) is a small tree that forms dense stands, displacing native plant species and threatening natural forest habitats in its introduced range in North America. Removal via cutting is labor intensive and often ineffective due to vigorous resprouting. Although chemical control methods are effective, they can negatively affect sensitive ecosystems. A mycoherbicide that selectively kills buckthorn would provide an additional method for control. In the present study, fungi were collected from dying buckthorn species (Frangula alnus Mill., Rhamnus cathartica, Ventia alnifolia L’Hér) located at 19 sites across Minnesota and Wisconsin for their potential use as mycoherbicides for common buckthorn. A total of 412 fungi were isolated from samples of diseased tissue and identified via DNA extraction and sequencing. These fungi were identified as 120 unique taxa belonging to 81 genera. Of these fungi, 46 species belonging to 26 genera were considered to be canker or root-rot pathogens of woody plants, including species in Cytospora, Diaporthe, Diplodia, Dothiorella, Eutypella, Fusarium, Hymenochaete, Irpex, Phaeoacemonium, and others. A future study testing the pathogenicity of these putative pathogens of buckthorn is now needed to assess their utility as potential mycoherbicide agents for control of common buckthorn. Full article

Background/Objectives: Branch dieback and canker diseases caused by Cytospora species adversely impact the health of woody plants worldwide. Results: During this survey, 59 Cytospora isolates were obtained from symptomatic trees and shrubs growing in southwest Ontario and Saskatchewan, Canada. A DNA barcoding approach combined with morphological characterization identified 15 known species of Cytospora associated with these diseases: C. chrysosperma, C. curvata, C. euonymina, C. hoffmannii, C. kantschavelii, C. leucosperma, C. leucostoma, C. nitschkeana, C. piceae, C. populina, C. pruinopsis, C. pruinosa, C. ribis, C. schulzeri, and C. sorbina. The most common species isolated from multiple hosts were C. sorbina (10), C. chrysosperma (8), C. nitschkeana (6), and C. pruinosa (6). A wide range of host associations, including non-conifer species, was observed for C. piceae. Conclusions: The obtained results contribute to the study of diversity, host affiliation, geographical distribution, and pathogenicity of Cytospora species occurring on woody plants in both natural habitats and agricultural systems. The findings support the effectiveness of using DNA barcodes in fungal taxonomy and plant pathology studies. Full article

Pear Valsa cankers were found in various Korla fragrant pear orchards in Alaer, Xinjiang. Disease samples underwent tissue isolation, resulting in six isolates. Pathogenicity tests revealed that the XLFL-6 isolate was the most virulent, demonstrating typical Valsa canker symptoms. Research on its biological characteristics indicated that the optimal growth conditions for XLFL-6 were a temperature of 28 °C and a pH of five. Under these conditions, the colonies of XLFL-6 exhibited the largest growth diameter, and adding glucose and peptone separately to the Czapek medium was most conducive to the growth of its mycelium. Based on morphological observations and multigene sequence analyses (ITS+TEF+TUB), the pathogenic fungus was identified as C. pyri. The infection process of C. pyri was elucidated through tissue observations using both light and electron microscopy. The conidia displayed a similar germination pattern on both wounded and intact twigs. However, the infection process was delayed in the case of intact bark. By 8 h post-inoculation, the conidia achieved a germination rate of 15%. Although germination had occurred, the infection process had not yet commenced. In contrast, for wounded bark tissue, it was observed that 24 h post-inoculation, the fungal hyphae from the conidia directly invaded the wounded tissue. These hyphae penetrate the cell walls, proliferate within the host tissue, and spread throughout the phloem and xylem. After 20 d, numerous pycnidia had breached the bark surface, and yellow waxy gums filled with conidia flowed abundantly from the pycnidia ostioles, with the host tissue being nearly totally disintegrated. Regarding enzyme activity, the polygalacturonase (PG) activity, the primary cell wall-degrading enzyme in the treatment group, was seven times greater than that of the control group. The carboxymethyl cellulose (Cx) activity within the treatment group continued to increase. Xylanase activity rose swiftly to its peak between days 1 and 4, then decreased from days 5 to 10, although it remained higher than that of the control group. Overall, this study is the first to provide a detailed report on the characteristics and proliferation of C. pyri and further elucidates its modes and pathways of invasion. Full article

Walnut canker is a common disease in the Xinjiang Uygur autonomous region of China, which is caused by Cytospora chrysosperma. To date, there is no effective control measure for this disease. Infection with mycoviruses has been widely proven to reduce the virulence of plant pathogenic fungi, with some mycoviruses even serving as potential biological control agents for plant diseases. In this study, mycoviruses associated with 31 strains of C. chrysosperma from Xinjiang Uygur autonomous region were identified by metatranscriptomic sequencing. Seven new mycoviruses were identified by BLAST and RT-PCR analysis, which were Botrytis cinerea partitivirus 5 (BcPV5), Gammapartitivirus sp-XJ1 (GVsp-XJ1), Botoulivirus sp-XJ2 (BVsp-XJ2), Luoyang Fusar tick virus 2 (LfTV2), Leptosphaeria biglobosa narnavirus 17 (LbNV17), Sclerotinia sclerotiorum narnavirus 6 (SsNV6), and Cytospora ribis mitovirus (CrMV3). Among these, BcPV5, GVsp-XJ1, BVsp-XJ2, CrMV3, and LfTV2 were found to co-infect C. chrysosperma strain WS-11 and significantly reduce both the colony growth rate and virulence of the host. After co-culturing the virus-free WS-FV strain with WS-11, the colony growth rate and virulence of the derivative strain were also decreased. These results provide potential biocontrol resources for the control of walnut canker. Full article

Apples are widely consumed by people all over the world due to their taste and nutritional value. However, apple trees are prone to various environmental stresses, including fungal diseases. Among them, Cytospora canker (or Valsa canker) can cause dieback of branches and twigs. Although Kazakhstan is well known as an origin of apples, very little is known about canker diseases that spread across all commercial orchards. Therefore, an accurate identification of the causal agents of those diseases is needed for further application of informed disease management strategies. In this study, eleven isolates belonging to four Cytospora species were isolated from multiple cultivars, grown in six different orchards within the Almaty region, Kazakhstan. As a result of a multilocus phylogenetic analysis using ITS, LSU and tef1-α marker genes and morphological characterization, these isolates were described as Cytospora parasitica, Cytospora sorbina, Cytospora pruinopsis and Cytospora chrysosperma. Moreover, a pathogenicity test was conducted on detached twigs, and it demonstrated that two of these fungi were highly virulent. Overall, this paper is a first report of the causal agents of apple canker disease in Kazakhstan and could be a trigger for conducting future studies to better understand the disease epidemiology, as well as build management strategies. Full article

Peach (Prunus persica) is widely cultivated in China, but fungal diseases, particularly Cytospora canker, significantly impact tree health, reducing fruit yield and economic value. This disease mainly weakens tree branches and trunks, sometimes leading to tree death. There are no updated studies on the diversity of Cytospora species associated with peach Cytospora canker in northern China. To determine the Cytospora species associated with this disease, we surveyed five provinces from 2022 to 2023, collecting 72 disease samples with symptoms including branches with black fruiting bodies, cankers, cracking, dieback, and gummosis. Through morphology and multi-loci phylogeny, 127 isolates were identified into four known (C. ailanthicola, C. erumpens, C. leucostoma, and C. leucosperma) and two previously undescribed species (C. gansuensis sp. nov. and C. qinanensis sp. nov.). Cytospora leucostoma (73.60%) was the most abundant. Pathogenicity tests indicated that except for C. ailanthicola, all other species were pathogenic to peach, with C. erumpens being the most aggressive. This study is the first to report the novel host association of C. erumpens on peaches globally and represents the first comprehensive investigation of Cytospora species associated with canker diseases in the main peach production area in northern China, offering a foundation for developing effective disease management strategies. Full article

The wood decay fungi Cytospora sorbicola and Calosphaeria pulchella severely threaten the worldwide cultivation of sweet cherry trees (Prunus avium L.). Both fungi cause similar symptoms, including vascular necrosis, which leads to branch and twig dieback. In advanced stages of the disease, cankers are visible on tree branches and trunks. The sweet cherry is the most widely planted fruit tree in Chile, with 74,000 hectares in 2023. According to the planted surface, the predominant sweet cherry varieties are Lapins, Santina, Regina, and Bing. Variety-dependent susceptibility studies on Cyt. sorbicola and Cal. pulchella are lacking. The main entry points for wood necrosis-causing fungi are pruning wounds; therefore, we evaluated the aggressiveness of Cyt. sorbicola and Cal. pulchella in one-year-old sweet cherry plants. Santina and Lapins showed the lowest necrotic lesion caused by Cyt. sorbicola (13.6 and 14.31 mm, respectively), followed by Bing (19.51 mm) and Regina (26.14 mm). All plants infected by Cyt. sorbicola showed shoot blight regardless of the variety. In addition, there was a varying susceptibility to Cal. pulchella, with Lapins (21.6 mm), Bing (22.83 mm), Santina (27.62 mm), and Regina (30.8 mm) showing increasing levels of observed necrosis. The lesion caused by Cal. pulchella was more significant than that observed for Cyt. sorbicola, regardless of the cherry tree genotype. We identified each fungal growth from the wood necrosis progression area using two independent novel PCR-HRM strategies based on the ITS fungal region, which allowed us to differentiate each pathogen of interest individually or simultaneously. This study demonstrates different levels of susceptibility of sweet cherry tree genotypes to wood-degrading pathogens, emphasizing the need to include these factors in phytosanitary management programs. Full article

Xinjiang is an important forest and fruit production area in China, and Cytospora canker, caused by the genus Cytospora Ehrenb., has caused serious losses to forestry production in Xinjiang. In this study, we constructed ensemble models based on Biomod2 to assess the potential geographical distribution of Cytospora chrysosperma, C. nivea, and C. mali in Xinjiang, China and their changes under different climate change scenarios, using species occurrence data and four types of environmental variables: bioclimatic, topographic, NDVI, and soil. The model performance assessment metrics (AUC and TSS) indicated that the ensemble models are highly reliable. The results showed that NDVI had the most important effect on the distribution of all three species, but there were differences in the response patterns, and bioclimatic factors such as temperature and precipitation also significantly affected the distribution of the three species. C. chrysosperma showed the broadest ecological adaptation and the greatest potential for expansion. C. nivea and C. mali also showed expansion trends, but to a lesser extent. The overlapping geographical distribution areas of the three species increased over time and with an intensification of the climate scenarios, especially under the high-emission SSP585 scenario. The centroids of the geographical distribution for all three species generally shifted towards higher latitude regions in the northeast, reflecting their response to climate warming. C. chrysosperma may become a more prevalent forest health threat in the future, and an increase in the overlapping geographical distribution areas of the three species may lead to an increased risk of multiple infections. These findings provide an important basis for understanding and predicting the distribution and spread of the genus Cytospora in Xinjiang and are important for the development of effective forest disease prevention and control strategies. Full article

Apple canker disease, also named as apple Valsa canker, is one of the most destructive diseases for apples (Malus domestica Borkh.). Cytospora/Valsa spp. are the dominant causal agent of this disease, but many studies have revealed that fungi from some other genus can also cause typical apple canker symptoms. In this study, we performed fungal pathogen isolation from cankered ‘Fuji’ apple barks. Six representative morphologically different fungi (Strain 1–6) were further subjected to ITS sequencing and evolutionary analysis. Molecular identification results revealed that Strains 1–6 are Cytospora mali, Fusarium cf. solani, Alternaria alternata, C. mali, Diplodia seriata and F. proliferatum, respectively. All these fungi have been reported to be causal agents of apple diseases. By inoculating fungal plugs onto trunks of ‘Fuji’ apple trees, the pathogenicity of the six fungi were accessed. Only the inoculations of the two C. mali strains (Strain 1 and Strain 4) and the A. alternata strain (Strain 3) resulted in typical apple canker symptoms in trunks. It is worth noting that Strain 1 caused much more severe canker symptoms and higher pathogenicity incidence than the other two fungi. A. alternata has been identified as a pathogen causing diseases on apple fruits and leaves. By further assessing its pathogenicity on apple fruits and leaves, we verified that it can also cause typical fruit rot and leaf spot symptoms. To the best of our knowledge, this is the first report on apple canker disease caused by A. alternata in China. Our present study can provide a theoretical foundation for the prevention and control of apple canker disease. Full article

Cytospora (Cytosporaceae, Diaporthales) is a fungal genus that usually inhabits plants as endophytes, saprobes, as well as pathogens. Species of this genus are characterized by possessing allantoid hyaline conidia and ascospores. Samples with typical Cytospora canker symptoms on Prunus davidiana, P. padus and Salix sp. were collected in Tibet and Xinjiang, China. Species were identified using both morphological and molecular approaches of combined loci of internal transcribed spacer region rDNA (ITS), the partial actin (act) region, RNA polymerase II second largest subunit (rpb2), the translation elongation factor 1-alpha (tef1) gene and the partial be-ta-tubulin (tub2) gene. Six isolates in the present study formed three distinct clades from previously known species. Cytospora hejingensis sp. nov. from Salix sp., C. jilongensis sp. nov. from P. davidiana and C. kunsensis from P. padus were proposed herein. The current study improves the understanding of species concept in Cytospora. Full article

Branch canker diseases are important in forest ecosystems, causing economic and ecological losses. Members of Cytospora are common on cankered branches and associated with the diseases. Investigations on Cytospora cankers were conducted in Tibet, China, during 2022 and 2023. Samples were collected from Euonymus japonicus, Larix gmelinii, Malus pumila, M. spectabilis and Rosa omeiensis f. pteracantha, and cultures were obtained and identified by morphological features and molecular phylogeny of a combination of internal transcribed spacer region rDNA (ITS), the partial actin (act) region, RNA polymerase II second largest subunit (rpb2) gene, the translation elongation factor 1-alpha (tef1) gene and the partial beta-tubulin (tub2) gene. As a result, a new species is proposed herein named Cytospora lhasaensis and four known species are described for the first time from Tibet, viz. C. euonymina, C. gigaspora, C. mali and C. schulzeri. The current research enhances our understanding of the Cytospora species associated with woody host diseases in Tibet, China. Full article

The plant pathogenic fungus Cytospora is notoriously known for causing woody plant canker diseases, resulting in substantial economic losses to biological forests and fruit trees worldwide. Despite their strong negative ecological impact, the existing and prospective distribution patterns of these plant pathogens in China, according to climate change, have received little attention. In this study, we chose three widely dispersed and seriously damaging species, namely, Cytospora chrysosperma, Cytospora mali, and Cytospora nivea, which are the most common species that damage the Juglans regia, Malus domestica, Eucalyptus, Pyrus sinkiangensis, Populus spp., and Salix spp. in China. We utilized ecological niche modeling to forecast their regional distribution in China under four climate change scenarios (present, SSP 126, SSP 370, and SSP 585). The results show that temperature-related climate factors limit the current distribution ranges of the three species. Currently, the three studied species are highly suitable for northeast, northwest, north, and southwest China. Under future climate scenarios, the distribution ranges of the three species are projected to increase, and the centers of the adequate distribution areas of the three species are expected to shift to high-latitude regions. The three species coexist in China, primarily in the northwest and north regions. The ecological niches of C. chrysosperma and C. nivea are more similar. The distribution range of C. mali can reach the warmer and wetter eastern region, whereas C. chrysosperma and C. nivea are primarily found in drought-prone areas with little rainfall. Our findings can help farmers and planners develop methods to avoid the spread of Cytospora spp. and calculate the costs of applying pesticides to reduce contamination and boost yields. Full article

Olive (Olea europaea L.) is a very important crop grown in the Mediterranean part of Croatia. Olive branch and fruit dieback symptoms were observed in two olive orchards in Istria, Croatia. The samples from symptomatic trees were collected and brought to the laboratory for analysis. Based on their morphological characterization, isolated fungi were identified as Cytospora sp. Two representative isolates (one per orchard) were taken for molecular analysis, and based on DNA sequence data of the ITS and TUB gene regions, and phylogenetic analysis of the sequences, the isolates were identified as Cytospora pruinosa Défago. To determine pathogenicity, pathogenicity tests were conducted on detached olive branches and two-year-old olive trees in the greenhouse. This is the first report of C. pruinosa causing olive branch and fruit dieback in Croatia. Full article

Pistachio (Pistacia vera) is an important Mediterranean crop. In Italy, pistachio is cultivated in the southern regions, of which Sicily is the main production area. Recently, the phytopathological situation of this crop has started to be updated, and new diseases have been discovered, studied, and reported. Botryosphaeriaceae spp. and Leptosillia pistaciae are major canker/rot pathogens, and Cytospora pistaciae and Eutypa lata have been reported as minor canker pathogens. In this paper, we evaluated different biological control agents, belonging to Trichoderma asperellum, T. atroviride and T. harzianum, as well as some Bacillus amyloliquefaciens strains, against above-mentioned pathogens. Results of dual culture assays showed that all the biological products, both fungi and bacteria, were able to inhibit the mycelial growth of the pathogens in vitro. Experiments using detached twigs showed no effect of biocontrol agents in reducing infections, except for Neofusicoccum hellenicum treated with T. harzianum T22 and Leptosillia pistaciae treated with B. amyloliquefaciens D747. Results of detached fruit experiments showed an efficacy ranging from 32.5 to 66.9% of all the biological products in reducing the lesions caused by N. mediterraneum. This study provides basic information for future research on biological control of pistachio diseases and future prospects for search of more effective biological control agents for canker diseases than those studied here. Full article

Species of Cytospora are considered important plant pathogens of a wide range of plant hosts, especially Salicaceae plants. Salix (Salicaceae, Malpighiales) has been widely cultivated in China because of its strong ecological adaptability, fast growth, and easy reproduction. In this study, a total of eight species of Cytospora were discovered on Salix in China, including C. ailanthicola, C. alba, C. chrysosperma, C. gigaspora, C. nivea, C. paracinnamomea, C. rostrata, and C. sophoriopsis. Among them, C. alba and C. paracinnamomea were identified as novel species based on morphology and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2 gene sequences and were confirmed as pathogens of willow canker disease by pathogenicity tests. The mycelial growth rates of strains from these two novel species (C. alba and C. paracinnamomea) had optimum temperatures of 21 to 22 °C and an optimum pH value of 5 to 6. The effectiveness of six carbon sources on the mycelial growth showed that fructose and maltose had the highest influence. Cytospora species richness was significantly positively correlated with dry and wet areas. This study represents a significant evaluation of Cytospora associated with willow canker disease in China and provides a theoretical basis for predicting the potential risk of willow canker disease. Full article