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Article

Fungi Associated with Dying Buckthorn in North America

by
Ryan D. M. Franke
*,
Nickolas N. Rajtar
and
Robert A. Blanchette
Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA
*
Author to whom correspondence should be addressed.
Forests 2025, 16(7), 1148; https://doi.org/10.3390/f16071148
Submission received: 16 June 2025 / Revised: 7 July 2025 / Accepted: 10 July 2025 / Published: 11 July 2025
(This article belongs to the Special Issue Pathogenic Fungi in Forest)
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Abstract

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.

1. Introduction

Common buckthorn (Rhamnus cathartica L.) was brought to North America in the late 1700s by European immigrants and has since become an invasive plant. It is now the focus of control by forest managers and landowners across a large swath of the continent. After its initial introduction, the shrub gained popularity as a cold-hardy, insect and pathogen-resistant ornamental hedge plant. Subsequently, its spread across the North-Eastern and Upper-Midwestern United States, as well as the Eastern and Central Canadian provinces, was facilitated by people who planted the shrub in their new locales as a hedge [1]. Currently, common buckthorn has invasive status in 16 states in the North-Eastern and Upper-Midwestern United States and is designated a noxious weed in the Canadian provinces of Alberta, Manitoba, and Ontario.
Common buckthorn’s combination of advantageous life history traits, few natural enemies, co-facilitation with invasive earthworms, and possibly other factors interact with the natural landscape in its introduced range to alter ecosystem dynamics and decrease native plant biodiversity [2,3,4,5]. Furthermore, common buckthorn serves as the overwintering host for two major agricultural pests, soybean aphid (Aphis glycines Matsumura) and oat crown rust (Puccinia coronata Corda), that cause significant agricultural losses [6].
Removing common buckthorn from a site is particularly challenging due to its ability to regenerate via stump sprouts and seedlings after initial removal [7]. Mechanical removal, while target-specific and environmentally sound, is very labor-intensive and not a viable option over large management areas [8]. In contrast, foliar herbicide applications or prescribed burning regimens can be cost-effective on large scales; however, these interventions can kill non-target vegetation and hinder the establishment of native plant species at restoration sites [9]. The shortcomings of current management techniques necessitate a better control method, such as a mycoherbicide that selectively kills buckthorn. This would be especially useful in closed-canopy forests where prescribed burning is undesirable, and in sensitive environmental areas where the risk of herbicide contamination precludes their use. Unfortunately, research evaluating Eurasian insects as classical biocontrol agents resulted in zero candidates for release in North America [10]. Globally, interest in mycoherbicides for unwanted woody plants was piqued with the release of BioChon, which used the fungus Chondrostereum purpureum to control black cherry and other hardwoods in the Netherlands in the late 1990s [11]. Since then, four additional canker fungi and one wilt fungus have been studied as active agents in three different mycoherbicides [11,12]. Management of common buckthorn using pathogenic fungi in a formulated mycoherbicide is largely unexplored. To date, just one fungus, C. purpureum, has been tested for its pathogenicity on common buckthorn, and its mycoherbicide formulations resulted in limited success [13,14].
Common buckthorn has inhabited the North American continent for at least 225 years, enough time to accumulate fungal pathogens in its introduced range according to the enemy release hypothesis [15]. However, information detailing its fungal natural enemies in North America (and Eurasia) is sparse [16]. Beginning in 2022, reports of locations with dying common buckthorn, glossy buckthorn (Frangula alnus, another unwanted introduced species), and alder-leaved buckthorn (Ventia alnifolia, a native and desirable species) were received from personnel at the Minnesota (USA) Department of Natural Resources, the Minnesota Department of Agriculture and the Wisconsin (USA) Department of Natural Resources. We hypothesized that buckthorn decline in its introduced range in Minnesota and Wisconsin is associated with particular fungal pathogens that may have utility as mycoherbicide agents for the control of common buckthorn.

2. Materials and Methods

2.1. Sample Collection and Isolation

Beginning in May 2023 through June 2024, samples of dying common buckthorn, glossy buckthorn, and alder-leaved buckthorn were collected in Minnesota and Wisconsin. Sites were located by Minnesota and Wisconsin state agency personnel, ecologically minded citizen scientists, and the authors. In all, 67 samples of suspect common buckthorn were obtained from 16 sites, 15 samples of glossy buckthorn were obtained from 4 sites, and 4 samples of alder-leaved buckthorn were obtained from 1 site. Alder-leaved buckthorn is uncommon in Minnesota, which limits sampling. Above and below ground plant tissue showing signs or symptoms was harvested with hand tools, transported to the lab, and stored at 4 °C until processed. Fungi were isolated from symptomatic plant tissues including stem dieback, diffuse cankers, localized cankers, and root rot by using a sterile scalpel to excise small segments of symptomatic tissue and culture onto three types of media: 1.5% malt extract agar containing 15 g of Difco Bacto agar (Apex Bioresearch Products, El Cajon, CA, USA), 15 g of Difco Bacto malt extract (Thermo Fisher, Detroit, MI, USA) per L of deinonized water with 0.1 g of streptomycin sulfate (Sigma-Aldrich, St Louis, MO, USA) added after autoclaving; modified Sabourad dextrose agar adapted from Harrington [17] containing 15 g of Difco Bacto agar, 15 g of Difco Bacto malt extract per L of deionized water with 0.1 g of cycloheximide (Sigma-Aldrich, St Louis, MO, USA) and 0.1 g streptomycin sulfate added after autoclaving; Basidiomycota selective agar adapted from Worrall [18] with 15 g of Difco Bacto agar, 15 g of Difco Bacto malt extract, 2 g of Difco Bacto yeast extract (Thermo Fisher, Detroit, MI, USA) and 0.06 g of benomyl (Santa Cruz Biotechnology, Dallas, TX, USA) per L of deinonized water with 0.1 g of streptomycin sulfate and 2 mL of lactic acid (Aqua Solutions, Deer Park, TX, USA) added after autoclaving. For each buckthorn sample, one pure culture was created for each unique hyphal growth form by removing the advancing hyphal tip region from the isolation media and plating on malt yeast extract agar (15 g of Difco Bacto agar, 15 g of Difco Bacto malt extract, and 2 g of Difco Bacto yeast extract per L of deionized water), except for growth forms resembling Mucoromycota, Trichoderma, and Penicillium, which were excluded from the study because they are not known to cause plant disease.

2.2. Molecular Identification

For each site, one representative isolate of each culture morphology was selected for molecular identification. DNA was extracted from pure cultures using the PrepMan Ultra Life Technologies Corporation, Carlsbad, CA, USA sample preparation reagent according to the manufacturer’s protocol. Polymerase chain reactions were set up for each DNA extract according to Blanchette et al. [19], and the internal transcribed spacer region of DNA was amplified with primer pair ITS1F/4 [20] using the touchdown program outlined by Korbie and Mattick [21]. Isolates in the Fusarium complex and Didymellaceae family were subjected to an additional PCR reaction amplifying a region of the RNA polymerase II gene [22,23] using primer pair RPB2-5f2 and RPB2-7cR [24,25]. Polymerase chain reactions were set up according to Blanchette et al. [19] using the thermocycle program developed by Hou et al. [22]. Amplicons were verified using 1% agarose gel electrophoresis with SYBR green I pre-stain (Life Technologies Corporation, Eugene, OR, USA) and visualized with transillumination on a Dark Reader DR45 (Clare Chemical Research, Dolores, CO, USA). Sanger sequencing was performed with PCR primers ITS1F (ITS) and RPB2-5f2 (RNA Polymerase II; Fusarium spp., Didymellaceae spp.) on an ABI 3730xl DNA sequencer (Applied Biosystems, Foster City, CA, USA). Sequences were trimmed using Geneious 11.1 (Dotmatics, Boston, MA, USA) [26] and run through the BLASTn algorithm [27] using the megablast option in NCBI GenBank. Sequences were identified by matching to a species-level accession from a peer-reviewed publication or type specimen with the highest percent nucleotide sequence similarity and query cover (max score). Sequences representative of each taxon were accessioned to GenBank and given species, genera, or higher-level classifications (Supplementary Tables S1–S3). Sequences matching less than 97% to a species accession from a published study were given genera classification. Sequences matching more than one species from published studies were also given genera classification. Taxa relative abundance was calculated on per sample basis (i.e., multiple isolates of the same taxon originating from the same sample were counted as one).

2.3. Lifestyle Classification

Lifestyles were designated for each genus subsequent to a review of the scientific literature produced by an online search of the genus of inquiry (e.g., “Diplodia”) plus the search terms “ecology” and “lifestyle”. If sources ascribed a genus to more than one lifestyle, the more frequently reported lifestyle was chosen as the designation. If search results provided insufficient evidence of lifestyle for a given genus, the lifestyle was designated as unknown for the genus. This approach risks misclassification for genera with diverse lifestyles and is a limitation of this study. A second online search was performed at the species level for each taxon, using the species name (e.g., Diplodia seriata) and the search term “pathogen”. Species were designated as putative pathogens of buckthorn if they had been described in the literature as causing stem canker, root disease, or wilt disease of a woody host.

3. Results

3.1. Common Buckhorn

The majority of sampled common buckthorn trees had long diffuse cankers along the stem (91.01%) (Figure 1). Of these trees, those with diffuse cankers comprised 71.64% of the total, while trees with diffuse cankers and fungal reproductive structures comprised 13.33%, and trees with diffuse cankers and white rot comprised an additional 3.33%. Fungi identified from cultures from the reproductive structures associated with these diffuse cankers and white rot included Irpex lacteus and Peniophora cinerea. A smaller fraction of common buckthorn trees sampled had root rot (8.96%). Trees with only root rot comprised 5.97% of total samples, whereas trees with root rot and reproductive structures comprised 2.99% of samples. The fungus identified from cultures from the reproductive structures associated with root rot was Xylaria polymorpha.
In total, 307 isolates were collected from common buckthorn. These isolates were identified as 82 unique taxa belonging to 67 genera (Figure 2). These genera are affiliated with 29 Ascomycota and 16 Basidiomycota families. The families of the Ascomycota belong to 4 classes and 14 orders (Acrospermales, Botryosphaeriales, Cladosporiales, Muyocopronales, Pleosporales, Helotiales, Calosphaeriales, Cephalothecales, Diaporthales, Hypocreales, Togniniales, Ophiostomatales, and Xylariales). The families of the Basidiomycota belong to two classes and six orders (Agaricales, Cantharellales, Coriceales, Hymenochaetales, Polyporales, and Russulales).

3.2. Glossy Buckhorn

The majority of sampled glossy buckthorn trees had localized cankers on the stem (60.00%) (Figure 3). Only one of these trees had white rot in addition to localized cankers. A smaller fraction of trees had diffuse cankers running lengthwise along the stem (33.33%). Of these trees, those with only diffuse cankers comprised 13.33% of the total, while trees with diffuse cankers and fungal reproductive structures comprised an additional 20.00%. Fungi isolated from beige-colored, ascomycete-like reproductive structures were primarily mycoparasites and thus likely not the fungi responsible for forming the reproductive structures. On the other hand, Diplodia corticola was isolated from the black, flask-shaped, ascomycete-like reproductive structures. Only one tree with root rot was sampled.
A total of 78 isolates were obtained from glossy buckthorn. These isolates were identified as 38 unique taxa belonging to 32 genera (Figure 4). These genera are affiliated with 22 Ascomycota and 3 Basidiomycota families. The Ascomycota families belong to 4 classes and 12 orders (Botryosphaeriales, Cladosporiales, Pleosporales, Chaetothyriales, Eurotiales, Helotiales, Calosphaeriales, Diaporthales, Glomerellales, Hypocreales, Togniniales, and Xylariales). The Basidiomycota families belong to one class and three orders (Agaricales, Polyporales, and Russulales).

3.3. Alder-Leaved Buckhorn

Of the four alder-leaved buckthorn (Rhamnus alnifolia L’Hér) trees sampled, one had a diffuse canker, whereas the others had only healthy tissues. Fungi were isolated from diffuse canker, healthy stem, and healthy root tissues (Figure 5). In total, 25 isolates were collected from alder-leaved buckthorn and identified as 16 unique taxa belonging to 15 genera (Figure 6). All genera belong to 14 Ascomycota families in four classes and eight orders (Cladosporiales, Pleosporales, Helotiales, Orbiliales, Diaporthales, Hypocreales, Ophiostomatales, and Xylariales).

3.4. Lifestyle Distribution and Potential Pathogens

Eight lifestyle strategies were established for the 81 genera occurring across the three buckthorn species. In descending order, the most abundant lifestyle was canker pathogenic (22 genera) followed by wood decay (13 genera), foliar pathogenic (8 genera), endophytic (5 genera), entomopathogenic (3 genera), root pathogenic (3 genera), soil saprophytic (3 genera), and mycoparasitic (2 genera) (Figure 7). Additionally, there were 22 genera for which there was insufficient ecological information to ascribe them to a lifestyle strategy.
Putative pathogens of buckthorn included 46 species belonging to 26 genera (Figure 8). Of these, 28 species were exclusive to common buckthorn, 7 species exclusive to glossy buckthorn, and 4 species exclusive to alder-leaved buckthorn. Additionally, five species were shared between common and glossy buckthorn, one species between common and alder-leaved buckthorn, and one species between all three buckthorn hosts.

4. Discussion

At three different sites, landowners described common buckthorn on their property as declining. Indeed, mature buckthorn growth at most of our sites was sparse compared to the dense thickets that are often formed in woodlands and forests in its introduced range. Although sparse, this mature growth often had undergrowth, with a thick carpet of buckthorn saplings. Some of these were also dying back.
Either diffuse or localized cankers on the main stem accompanied dieback in most of the trees at the majority of sites. The prevalence of these cankers in dying buckthorn may indicate the importance of canker-causing fungi in the disease dynamics of buckthorn species. Less frequently encountered were symptoms of root disease, present in just 5 of 87 sampled trees; however, it is possible that some occurrences of root disease were overlooked, being belowground and obscured from sight. Widespread symptoms of wilt disease were not found in this study.
Previous studies have shown that a release from mammalian and insect natural enemies may contribute to common buckthorn’s success in its introduced range [28,29,30,31,32,33]. In contrast, other research has demonstrated that common buckthorn may be more susceptible to North American soil-borne pathogens than Eurasian soil pathogens [34]. A survey of the fungi associated with common buckthorn on both continents reveals a list of possible pathogenic associations, but none of these fungi have been tested for their ability to cause disease in common buckthorn. Records from Europe show seven putative cankers and no root pathogenic fungi collected from common buckthorn. These putative canker fungi include Biscogniauxia simplicior, Diaporthe fibrosa, Eutypa lata, Eutypella extensa, Fomitiporia punctata, Leucostoma persoonii, and Phellinus rhamni [16]. Records from North America, including the collections made in this study, show 26 putative canker pathogenic and 5 putative root pathogenic fungi associated with common buckthorn that have not been reported from common buckthorn in Europe. Only two putative canker pathogenic species have been collected from common buckthorn on both continents (Diaporthe fibrosa and Fomitiporia punctata) [16]. The discrepancy in the number of putative canker and root pathogenic fungi collected from common buckthorn on the Eurasian and North American continents is likely due to sampling bias, as 28 of the 32 putative canker and root pathogenic fungi reported from North America were collected as part of two independent studies investigating the fungal community associated with common buckthorn in its introduced range. No such comparable study exists from Europe. Sampling bias notwithstanding, common buckthorn has occupied the North American continent for at least 225 years, with its range extending across most of the Eastern broadleaf forest, and according to the enemy release hypothesis, may have accumulated new fungal natural enemies in its introduced range during this time [15,35]. Pathogenicity testing of the putative pathogenic fungi collected in this study is needed, but is beyond the scope of this exploratory study.
Due to unequal sampling between the three species of buckthorn, a beta diversity index could not be calculated to quantify differences in community composition across buckthorn hosts. However, our data describe differences between the compositions of putative pathogenic fungi associated with each buckthorn host species. For instance, only one putative canker pathogenic species, Nothophoma quercina, was isolated from all three buckthorn species, whereas 25, 7, and 4 putative pathogenic canker species were exclusively isolated from common, glossy, and alder-leaved buckthorn, respectively. However, some of these host-specific fungal associations may not retain their host-specificity under a more even and larger sampling scheme for all three buckthorn species. Spillover and spillback of pathogens from invasive to native hosts are well documented in the field of invasion biology [36,37]. In locales where populations of native alder-leaved buckthorn and invasive buckthorn species overlap, spilling of Nothophoma quercina or Fusarium acuminatum (isolated from both common buckthorn and alder-leaved buckthorn) may occur between native and invasive hosts. Furthermore, a larger sample size from native alder-leaved buckthorn could reveal more putative pathogens associated with both native and invasive buckthorn species and thus capable of spillover/spillback. Host genotype is an important factor determining the position of a fungus on the continuum of symbiosis, affecting plant–fungus interaction outcomes [38]. An outstanding example is the dual lifestyle of Fusarium graminearum, as a pathogen in wheat (Triticum aestivum) and also a harmless endophyte in North American grass species (Elymus spp.) [39]. Hence, all putative canker and root pathogenic fungi, regardless of buckthorn host origin, should be considered as potential mycoherbicide candidates for common buckthorn and should be included in pathogenicity testing. Furthermore, these candidates should be evaluated for their potential to spill onto and harm populations of native buckthorn.
Numerous research projects across the globe have investigated the possibility of using locally occurring fungi to control unwanted populations of woody plants, with varying degrees of success [11,12,14]. One fungus in the Basidiomycota found in our study, Cylindrobasidium evolvens, is the active ingredient in the South African product, Stumpout®, which is used as a mycoherbicide for black wattle (Acacia mearnsii) and golden wattle (Acacia pycnantha) [40]. The pan-global Basidiomycota fungus, Chondrostereum purpureum (not found in our study), has been tested as a mycoherbicide for common buckthorn, with moderate efficacy [13,14]. From our study, we report 46 fungi found on dying buckthorn in the United States that have been documented as stem or root pathogens of woody hosts. A future study testing the pathogenicity of these fungi on common buckthorn is now needed to select potential mycoherbicide candidate species for common buckthorn.

5. Conclusions

We found 46 putatively pathogenic species of fungi associated with declining common, glossy, and alder-leaved buckthorn in Minnesota and Wisconsin, USA. This included many known canker, wilt, and root rot fungi, including Cytospora, Diaporthe, Diplodia, Dothiorella, Eutypella, Fusarium, Hymenochaete, Irpex, Phaeoacemonium, and others. The next step will be a study to test the pathogenicity of these fungi to assess their utility as mycoherbicide candidate species for controlling common buckthorn.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/f16071148/s1, Table S1. Common Buckthorn Genbank Accessions; Table S2. Glossy Buckthorn Genbank Accessions; Table S3. Alder-leaved Buckthorn Genbank Accessions.

Author Contributions

Conceptualization, R.D.M.F., N.N.R. and R.A.B.; methodology, R.D.M.F., N.N.R. and R.A.B.; formal analysis, R.D.M.F.; investigation, R.D.M.F., N.N.R. and R.A.B.; data curation, R.D.M.F.; writing—original draft preparation, R.D.M.F.; writing—review and editing, R.D.M.F., N.N.R. and R.A.B.; visualization, R.D.M.F.; supervision, R.A.B.; project administration, R.A.B.; funding acquisition, N.N.R. and R.A.B. All authors have read and agreed to the published version of the manuscript.

Funding

Funding for the project was provided by the Minnesota Environment and Natural Resources Trust Fund, Minnesota Invasive Terrestrial Plants and Pests Center, and United States Department of Agriculture Hatch project MIN22-089.

Data Availability Statement

The original data presented in the study are openly available in NCBI Genbank under the Accession numbers published in Supplementary Tables S1–S3.

Acknowledgments

We thank the Minnesota Department of Agriculture, Minnesota Department of Natural Resources, Wisconsin Department of Natural Resources, University of Minnesota Extension, Friends of the Mississippi River, and Bill Perkins for their assistance with site location and sample collection. We thank Amelia Lochridge, Evan Worrell, Jennifer Galarneau, and Benjamin Held for their assistance in the laboratory.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Figure 1. Signs and symptoms of fungi on common buckthorn (Rhamnus cathartica L.) samples.
Figure 1. Signs and symptoms of fungi on common buckthorn (Rhamnus cathartica L.) samples.
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Figure 2. Taxonomy of fungi isolated from 67 common buckthorn (Rhamnus cathartica L.) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
Figure 2. Taxonomy of fungi isolated from 67 common buckthorn (Rhamnus cathartica L.) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
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Figure 3. Signs and symptoms of fungi on glossy buckthorn (Frangula alnus Mill.) samples.
Figure 3. Signs and symptoms of fungi on glossy buckthorn (Frangula alnus Mill.) samples.
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Figure 4. Taxonomy of fungi isolated from 15 glossy buckthorn (Frangula alnus Mill.) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
Figure 4. Taxonomy of fungi isolated from 15 glossy buckthorn (Frangula alnus Mill.) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
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Figure 5. Signs and symptoms of fungi on alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples.
Figure 5. Signs and symptoms of fungi on alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples.
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Figure 6. Taxonomy of fungi isolated from four alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
Figure 6. Taxonomy of fungi isolated from four alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples. Fungal identity determined by the best BLAST match (%) to genus/species using ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). A count was recorded for each genus/species as the number of buckthorn trees from which the genus/species was isolated.
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Figure 7. Lifestyle strategy distribution of genera collected from common buckthorn (Rhamnus cathartica L.), glossy buckthorn (Frangula almus Mill.), and alder-leaved buckthorn (Rhamnus alnifolia L’Hér).
Figure 7. Lifestyle strategy distribution of genera collected from common buckthorn (Rhamnus cathartica L.), glossy buckthorn (Frangula almus Mill.), and alder-leaved buckthorn (Rhamnus alnifolia L’Hér).
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Figure 8. Fungi collected from 67 common buckthorn (Rhamnus cathartica L.), 15 glossy buckthorn (Frangula almus Mill.), and 4 alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples that have been reported in the scientific literature as causing stem cankers, root rots, or wilt diseases in other woody hosts. Fungi within overlapping circles were collected from more than one host. Fungal identity determined by the best BLAST match (%) to genus/species using the ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). The numbers in parentheses indicate the number of trees of the corresponding buckthorn host from which the species was isolated.
Figure 8. Fungi collected from 67 common buckthorn (Rhamnus cathartica L.), 15 glossy buckthorn (Frangula almus Mill.), and 4 alder-leaved buckthorn (Rhamnus alnifolia L’Hér) samples that have been reported in the scientific literature as causing stem cankers, root rots, or wilt diseases in other woody hosts. Fungi within overlapping circles were collected from more than one host. Fungal identity determined by the best BLAST match (%) to genus/species using the ITS sequence or RPB2 for Didymellaceae and Fusarium species (BLASTn algorithm using the megablast option in NCBI GenBank). The numbers in parentheses indicate the number of trees of the corresponding buckthorn host from which the species was isolated.
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Franke, R.D.M.; Rajtar, N.N.; Blanchette, R.A. Fungi Associated with Dying Buckthorn in North America. Forests 2025, 16, 1148. https://doi.org/10.3390/f16071148

AMA Style

Franke RDM, Rajtar NN, Blanchette RA. Fungi Associated with Dying Buckthorn in North America. Forests. 2025; 16(7):1148. https://doi.org/10.3390/f16071148

Chicago/Turabian Style

Franke, Ryan D. M., Nickolas N. Rajtar, and Robert A. Blanchette. 2025. "Fungi Associated with Dying Buckthorn in North America" Forests 16, no. 7: 1148. https://doi.org/10.3390/f16071148

APA Style

Franke, R. D. M., Rajtar, N. N., & Blanchette, R. A. (2025). Fungi Associated with Dying Buckthorn in North America. Forests, 16(7), 1148. https://doi.org/10.3390/f16071148

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