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Donald D Davis - One of the best experts on this subject based on the ideXlab platform.
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genome sequence of a lethal vascular wilt fungus verticillium nonalfalfae a biological control used against the invasive Ailanthus altissima
Microbiology Resource Announcements, 2019Co-Authors: Matthew T Kasson, Donald D Davis, Lindsay R Kasson, Kristen L Wickert, Jason E StajichAbstract:Verticillium nonalfalfae, a cosmopolitan soil-borne phytopathogen, causes vascular wilt in agricultural crops and perennial woody plants. Select strains of V. nonalfalfae can cause lethal disease in the invasive tree Ailanthus altissima and several have since been utilized as a biological control (biocontrol) against this widespread invader. Here, we report the genome sequence and annotation of V. nonalfalfae strain VnAa140/NRRL 66861.
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seed production viability and reproductive limits of the invasive Ailanthus altissima tree of heaven within invaded environments
Forests, 2017Co-Authors: Kristen L Wickert, Donald D Davis, Eric S Oneal, Matthew T KassonAbstract:The success of some invasive tree species is attributed, in part, to high fecundity in the form of sexual propagules. If invasive trees produce more seed annually than co-occurring native trees, they will have a greater ability to disperse and establish across the landscape. In this study, seed production of female Ailanthus trees was investigated to determine (1) reproductive age limits; (2) annual and cumulative seed output; and (3) seed viability. Existing data on Ailanthus seed production were combined with a novel dataset to compare variability in seed production and explore relationships with tree diameter and age. Results from this study showed Ailanthus’ reproductive window is exceptional, spanning more than a century, with seed viability exceeding 65% from a 104-year-old individual. Germination studies and complementary tetrazolium assays also confirmed high propagule viability from a 7-year-old Ailanthus and supports tetrazolium assays as a proxy for germination studies. Not only can individual Ailanthus produce >1 million seeds annually, but a significant relationship exists between seed production and tree diameter. Using this relationship, cumulative seed production in individual Ailanthus can reach ca. 10 and 52 million seeds over a 40-year and 100-year period, respectively. This study provides a comprehensive investigation of various facets of the reproductive potential of Ailanthus.
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intraspecific root grafts and clonal growth within Ailanthus altissima stands influence verticillium nonalfalfae transmission
Plant Disease, 2015Co-Authors: E S Oneal, Donald D DavisAbstract:Verticillium nonalfalfae, causal agent of Verticillium wilt, is being considered as a biocontrol for the highly invasive Ailanthus altissima in Pennsylvania. This soilborne fungus is extremely virulent on Ailanthus and rapidly transmitted from diseased to healthy trees within Ailanthus stands. The rapid transmission of the fungus could be facilitated by root grafts, but neither root graft formation in Ailanthus nor Verticillium transmission by root grafts in trees has been reported. Here, V. nonalfalfae transmission between diseased and healthy Ailanthus trees via intraspecific root grafts and clonal growth is evaluated. Using air-spade excavation, dye translocation, and root graft inoculations, functional root grafts were detected between Ailanthus trees and transmission of V. nonalfalfae across root grafts demonstrated. Inoculation of one Ailanthus parent stem resulted in 187 root sprouts showing Verticillium wilt symptoms 12 months after inoculation. This study revealed that clonal growth and root grafts, normally advantageous growth habits, leave Ailanthus stands vulnerable to widespread V. nonalfalfae infection. This study also broadens the understanding of the Ailanthus-Verticillium pathosystem, growth strategies of invasive Ailanthus, and epidemiology of Verticillium wilt within trees.
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expanded host range testing for verticillium nonalfalfae potential biocontrol agent against the invasive Ailanthus altissima
Plant Disease, 2015Co-Authors: Matthew T Kasson, E S Oneal, Donald D DavisAbstract:The naturally occurring Verticillium nonalfalfae has been proposed as a biocontrol agent against the highly invasive Ailanthus altissima in the eastern United States. We tested 71 nontarget woody species for susceptibility to the potential biocontrol agent. In the field, only devil’s walkingstick (17% incidence) and striped maple (3%) acquired infections through natural spread from infected A. altissima (100%). Staghorn sumac (16% incidence) also exhibited wilt in close proximity to diseased Ailanthus, although V. nonalfalfae was never recovered. Stem inoculations, which are highly artificial in that they bypass root defenses and flood the xylem with millions of conidia, induced varying levels of wilt and mortality in 10 nontarget species from which V. nonalfalfae was reisolated, although recovery and crown rebuilding occurred following initial wilt in several species including sassafras and northern catalpa. Thirty-seven of the 71 inoculated species exhibited vascular discoloration, although 23 of these ...
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first report of verticillium wilt caused by verticillium nonalfalfae on tree of heaven Ailanthus altissima in ohio
Plant Disease, 2013Co-Authors: J Rebbeck, Matthew T Kasson, E S Oneal, M A Malone, Dylan P G Short, Donald D DavisAbstract:Verticillium wilt of the highly invasive tree-of-heaven [Ailanthus altissima (Mill.) Swingle], caused by Verticillium nonalfalfae Interbitzin et al. (1), formerly classified as V. albo-atrum Reinke and Berthold, has been reported in the United States from two states: Pennsylvania (2) and Virginia (3). Infected A. altissima in both states exhibited similar symptoms of wilt, premature defoliation, terminal dieback, yellow vascular discoloration, and mortality. In June 2012, the second author observed dead and dying A. altissima trees in southern Ohio (Pike County) that exhibited symptoms similar to those on diseased A. altissima trees in Pennsylvania and Virginia. Samples were collected from stems of three symptomatic A. altissima trees and sent to Penn State for morphological and molecular identification. Immediately upon arrival, samples were surface-disinfected and plated onto plum extract agar (PEA), a semi-selective medium for Verticillium spp., amended with neomycin and streptomycin (2). The samples yielded six isolates, two from each of the three symptomatic trees, all of which were putatively identified as V. nonalfalfae based on the presence of verticillate conidiophores and formation of melanized hyphae. DNA was extracted from three isolates and molecular analyses performed using known primers (1) coding for elongation factor 1-alpha (EF), glyceraldehyde-3-phosphate dehydrogenase (GPD), and tryptophan synthase (TS). A BLAST search generated sequences that revealed 100% similarity to V. nonalfalfae for all three protein coding genes among the three Ohio isolates and reference sequences from Ailanthus, including isolates VnAaPA140 (GenBank Accession Nos. KC307764, KC307766, and KC307768) and VnAaVA2 (KC307758, KC307759, and KC307760), as well as isolate PD592 from potato (JN188227, JN188163, and JN188035), thereby confirming taxonomic placement of the Ohio Ailanthus isolates among those recovered from Ailanthus in Pennsylvania and Virginia. Aligned sequences from one representative isolate, VnAaOH1, were deposited into GenBank as accessions KC307761 (EF), KC307762 (GPD), and KC307763 (TS). In August 2012, the pathogenicity of all six isolates was confirmed by root-dipping 10 healthy 3-week-old A. altissima seedlings (seeds collected in University Park, PA) into conidial suspensions of 1 × 107 cfu/ml, wherein all inoculated seedlings wilted and died within 4 and 9 weeks, respectively. V. nonalfalfae was reisolated from all inoculated seedlings; control seedlings inoculated with distilled water remained asymptomatic. Ohio is the third state from which V. nonalfalfae has been reported to be pathogenic on A. altissima. If V. nonalfalfae proves to be widespread, it may represent a natural biocontrol for the invasive A. altissima. Also, since USDA APHIS evaluates and regulates new potential biocontrol agents on a state-by-state basis, it is important to document each state in which V. nonalfalfae is killing A. altissima, so that in-state inoculum can be used for biocontrol efforts, simplifying the regulatory process. References: (1) P. Inderbitzin et al. 2011 PLoS ONE, 6, e28341, 2011. (2) M. J. Schall and D. D. Davis. Plant Dis. 93:747, 2009. (3) A. L. Snyder et al. Plant Dis. 96:837, 2013.
Matthew T Kasson - One of the best experts on this subject based on the ideXlab platform.
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genome sequence of a lethal vascular wilt fungus verticillium nonalfalfae a biological control used against the invasive Ailanthus altissima
Microbiology Resource Announcements, 2019Co-Authors: Matthew T Kasson, Donald D Davis, Lindsay R Kasson, Kristen L Wickert, Jason E StajichAbstract:Verticillium nonalfalfae, a cosmopolitan soil-borne phytopathogen, causes vascular wilt in agricultural crops and perennial woody plants. Select strains of V. nonalfalfae can cause lethal disease in the invasive tree Ailanthus altissima and several have since been utilized as a biological control (biocontrol) against this widespread invader. Here, we report the genome sequence and annotation of V. nonalfalfae strain VnAa140/NRRL 66861.
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seed production viability and reproductive limits of the invasive Ailanthus altissima tree of heaven within invaded environments
Forests, 2017Co-Authors: Kristen L Wickert, Donald D Davis, Eric S Oneal, Matthew T KassonAbstract:The success of some invasive tree species is attributed, in part, to high fecundity in the form of sexual propagules. If invasive trees produce more seed annually than co-occurring native trees, they will have a greater ability to disperse and establish across the landscape. In this study, seed production of female Ailanthus trees was investigated to determine (1) reproductive age limits; (2) annual and cumulative seed output; and (3) seed viability. Existing data on Ailanthus seed production were combined with a novel dataset to compare variability in seed production and explore relationships with tree diameter and age. Results from this study showed Ailanthus’ reproductive window is exceptional, spanning more than a century, with seed viability exceeding 65% from a 104-year-old individual. Germination studies and complementary tetrazolium assays also confirmed high propagule viability from a 7-year-old Ailanthus and supports tetrazolium assays as a proxy for germination studies. Not only can individual Ailanthus produce >1 million seeds annually, but a significant relationship exists between seed production and tree diameter. Using this relationship, cumulative seed production in individual Ailanthus can reach ca. 10 and 52 million seeds over a 40-year and 100-year period, respectively. This study provides a comprehensive investigation of various facets of the reproductive potential of Ailanthus.
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expanded host range testing for verticillium nonalfalfae potential biocontrol agent against the invasive Ailanthus altissima
Plant Disease, 2015Co-Authors: Matthew T Kasson, E S Oneal, Donald D DavisAbstract:The naturally occurring Verticillium nonalfalfae has been proposed as a biocontrol agent against the highly invasive Ailanthus altissima in the eastern United States. We tested 71 nontarget woody species for susceptibility to the potential biocontrol agent. In the field, only devil’s walkingstick (17% incidence) and striped maple (3%) acquired infections through natural spread from infected A. altissima (100%). Staghorn sumac (16% incidence) also exhibited wilt in close proximity to diseased Ailanthus, although V. nonalfalfae was never recovered. Stem inoculations, which are highly artificial in that they bypass root defenses and flood the xylem with millions of conidia, induced varying levels of wilt and mortality in 10 nontarget species from which V. nonalfalfae was reisolated, although recovery and crown rebuilding occurred following initial wilt in several species including sassafras and northern catalpa. Thirty-seven of the 71 inoculated species exhibited vascular discoloration, although 23 of these ...
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first report of verticillium wilt caused by verticillium nonalfalfae on tree of heaven Ailanthus altissima in ohio
Plant Disease, 2013Co-Authors: J Rebbeck, Matthew T Kasson, E S Oneal, M A Malone, Dylan P G Short, Donald D DavisAbstract:Verticillium wilt of the highly invasive tree-of-heaven [Ailanthus altissima (Mill.) Swingle], caused by Verticillium nonalfalfae Interbitzin et al. (1), formerly classified as V. albo-atrum Reinke and Berthold, has been reported in the United States from two states: Pennsylvania (2) and Virginia (3). Infected A. altissima in both states exhibited similar symptoms of wilt, premature defoliation, terminal dieback, yellow vascular discoloration, and mortality. In June 2012, the second author observed dead and dying A. altissima trees in southern Ohio (Pike County) that exhibited symptoms similar to those on diseased A. altissima trees in Pennsylvania and Virginia. Samples were collected from stems of three symptomatic A. altissima trees and sent to Penn State for morphological and molecular identification. Immediately upon arrival, samples were surface-disinfected and plated onto plum extract agar (PEA), a semi-selective medium for Verticillium spp., amended with neomycin and streptomycin (2). The samples yielded six isolates, two from each of the three symptomatic trees, all of which were putatively identified as V. nonalfalfae based on the presence of verticillate conidiophores and formation of melanized hyphae. DNA was extracted from three isolates and molecular analyses performed using known primers (1) coding for elongation factor 1-alpha (EF), glyceraldehyde-3-phosphate dehydrogenase (GPD), and tryptophan synthase (TS). A BLAST search generated sequences that revealed 100% similarity to V. nonalfalfae for all three protein coding genes among the three Ohio isolates and reference sequences from Ailanthus, including isolates VnAaPA140 (GenBank Accession Nos. KC307764, KC307766, and KC307768) and VnAaVA2 (KC307758, KC307759, and KC307760), as well as isolate PD592 from potato (JN188227, JN188163, and JN188035), thereby confirming taxonomic placement of the Ohio Ailanthus isolates among those recovered from Ailanthus in Pennsylvania and Virginia. Aligned sequences from one representative isolate, VnAaOH1, were deposited into GenBank as accessions KC307761 (EF), KC307762 (GPD), and KC307763 (TS). In August 2012, the pathogenicity of all six isolates was confirmed by root-dipping 10 healthy 3-week-old A. altissima seedlings (seeds collected in University Park, PA) into conidial suspensions of 1 × 107 cfu/ml, wherein all inoculated seedlings wilted and died within 4 and 9 weeks, respectively. V. nonalfalfae was reisolated from all inoculated seedlings; control seedlings inoculated with distilled water remained asymptomatic. Ohio is the third state from which V. nonalfalfae has been reported to be pathogenic on A. altissima. If V. nonalfalfae proves to be widespread, it may represent a natural biocontrol for the invasive A. altissima. Also, since USDA APHIS evaluates and regulates new potential biocontrol agents on a state-by-state basis, it is important to document each state in which V. nonalfalfae is killing A. altissima, so that in-state inoculum can be used for biocontrol efforts, simplifying the regulatory process. References: (1) P. Inderbitzin et al. 2011 PLoS ONE, 6, e28341, 2011. (2) M. J. Schall and D. D. Davis. Plant Dis. 93:747, 2009. (3) A. L. Snyder et al. Plant Dis. 96:837, 2013.
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the invasive Ailanthus altissima in pennsylvania a case study elucidating species introduction migration invasion and growth patterns in the northeastern us
Northeastern Naturalist, 2013Co-Authors: Matthew T Kasson, Matthew D Davis, Donald D DavisAbstract:Abstract Ailanthus altissima (Tree of Heaven), an invasive tree species native to China and East Asia, was first introduced into the US ca. 1784 by William Hamilton at his Philadelphia, PA estate. However, the means and temporal progression of spread from this and other early points of introduction are not clear. This species now occurs in >40 US states, primarily as an urban and roadside weed. The Northeast supports the highest densities of Ailanthus within the US, mainly in transportation corridors and urban areas, where it has become the dominant tree species. A recent, widespread increase in Ailanthus incidence in eastern hardwood forests, not unlike prior invasions along railways and roadsides, suggests that current conditions favor invasion in natural environments. To help elucidate the life history of Ailanthus in Pennsylvania and the northeastern US, as well as answer fundamental biological questions concerning this species, we conducted dendrochronological (tree-ring) studies and floristic survey...
E S Oneal - One of the best experts on this subject based on the ideXlab platform.
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intraspecific root grafts and clonal growth within Ailanthus altissima stands influence verticillium nonalfalfae transmission
Plant Disease, 2015Co-Authors: E S Oneal, Donald D DavisAbstract:Verticillium nonalfalfae, causal agent of Verticillium wilt, is being considered as a biocontrol for the highly invasive Ailanthus altissima in Pennsylvania. This soilborne fungus is extremely virulent on Ailanthus and rapidly transmitted from diseased to healthy trees within Ailanthus stands. The rapid transmission of the fungus could be facilitated by root grafts, but neither root graft formation in Ailanthus nor Verticillium transmission by root grafts in trees has been reported. Here, V. nonalfalfae transmission between diseased and healthy Ailanthus trees via intraspecific root grafts and clonal growth is evaluated. Using air-spade excavation, dye translocation, and root graft inoculations, functional root grafts were detected between Ailanthus trees and transmission of V. nonalfalfae across root grafts demonstrated. Inoculation of one Ailanthus parent stem resulted in 187 root sprouts showing Verticillium wilt symptoms 12 months after inoculation. This study revealed that clonal growth and root grafts, normally advantageous growth habits, leave Ailanthus stands vulnerable to widespread V. nonalfalfae infection. This study also broadens the understanding of the Ailanthus-Verticillium pathosystem, growth strategies of invasive Ailanthus, and epidemiology of Verticillium wilt within trees.
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expanded host range testing for verticillium nonalfalfae potential biocontrol agent against the invasive Ailanthus altissima
Plant Disease, 2015Co-Authors: Matthew T Kasson, E S Oneal, Donald D DavisAbstract:The naturally occurring Verticillium nonalfalfae has been proposed as a biocontrol agent against the highly invasive Ailanthus altissima in the eastern United States. We tested 71 nontarget woody species for susceptibility to the potential biocontrol agent. In the field, only devil’s walkingstick (17% incidence) and striped maple (3%) acquired infections through natural spread from infected A. altissima (100%). Staghorn sumac (16% incidence) also exhibited wilt in close proximity to diseased Ailanthus, although V. nonalfalfae was never recovered. Stem inoculations, which are highly artificial in that they bypass root defenses and flood the xylem with millions of conidia, induced varying levels of wilt and mortality in 10 nontarget species from which V. nonalfalfae was reisolated, although recovery and crown rebuilding occurred following initial wilt in several species including sassafras and northern catalpa. Thirty-seven of the 71 inoculated species exhibited vascular discoloration, although 23 of these ...
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first report of verticillium wilt caused by verticillium nonalfalfae on tree of heaven Ailanthus altissima in ohio
Plant Disease, 2013Co-Authors: J Rebbeck, Matthew T Kasson, E S Oneal, M A Malone, Dylan P G Short, Donald D DavisAbstract:Verticillium wilt of the highly invasive tree-of-heaven [Ailanthus altissima (Mill.) Swingle], caused by Verticillium nonalfalfae Interbitzin et al. (1), formerly classified as V. albo-atrum Reinke and Berthold, has been reported in the United States from two states: Pennsylvania (2) and Virginia (3). Infected A. altissima in both states exhibited similar symptoms of wilt, premature defoliation, terminal dieback, yellow vascular discoloration, and mortality. In June 2012, the second author observed dead and dying A. altissima trees in southern Ohio (Pike County) that exhibited symptoms similar to those on diseased A. altissima trees in Pennsylvania and Virginia. Samples were collected from stems of three symptomatic A. altissima trees and sent to Penn State for morphological and molecular identification. Immediately upon arrival, samples were surface-disinfected and plated onto plum extract agar (PEA), a semi-selective medium for Verticillium spp., amended with neomycin and streptomycin (2). The samples yielded six isolates, two from each of the three symptomatic trees, all of which were putatively identified as V. nonalfalfae based on the presence of verticillate conidiophores and formation of melanized hyphae. DNA was extracted from three isolates and molecular analyses performed using known primers (1) coding for elongation factor 1-alpha (EF), glyceraldehyde-3-phosphate dehydrogenase (GPD), and tryptophan synthase (TS). A BLAST search generated sequences that revealed 100% similarity to V. nonalfalfae for all three protein coding genes among the three Ohio isolates and reference sequences from Ailanthus, including isolates VnAaPA140 (GenBank Accession Nos. KC307764, KC307766, and KC307768) and VnAaVA2 (KC307758, KC307759, and KC307760), as well as isolate PD592 from potato (JN188227, JN188163, and JN188035), thereby confirming taxonomic placement of the Ohio Ailanthus isolates among those recovered from Ailanthus in Pennsylvania and Virginia. Aligned sequences from one representative isolate, VnAaOH1, were deposited into GenBank as accessions KC307761 (EF), KC307762 (GPD), and KC307763 (TS). In August 2012, the pathogenicity of all six isolates was confirmed by root-dipping 10 healthy 3-week-old A. altissima seedlings (seeds collected in University Park, PA) into conidial suspensions of 1 × 107 cfu/ml, wherein all inoculated seedlings wilted and died within 4 and 9 weeks, respectively. V. nonalfalfae was reisolated from all inoculated seedlings; control seedlings inoculated with distilled water remained asymptomatic. Ohio is the third state from which V. nonalfalfae has been reported to be pathogenic on A. altissima. If V. nonalfalfae proves to be widespread, it may represent a natural biocontrol for the invasive A. altissima. Also, since USDA APHIS evaluates and regulates new potential biocontrol agents on a state-by-state basis, it is important to document each state in which V. nonalfalfae is killing A. altissima, so that in-state inoculum can be used for biocontrol efforts, simplifying the regulatory process. References: (1) P. Inderbitzin et al. 2011 PLoS ONE, 6, e28341, 2011. (2) M. J. Schall and D. D. Davis. Plant Dis. 93:747, 2009. (3) A. L. Snyder et al. Plant Dis. 96:837, 2013.
Ingo Kowarik - One of the best experts on this subject based on the ideXlab platform.
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Between approval and disapproval: Citizens’ views on the invasive tree Ailanthus altissima and its management
'Pensoft Publishers', 2021Co-Authors: Ingo Kowarik, Tanja M. Straka, Mario Lehmann, Rafael Studnitzky, Leonie K. FischerAbstract:While cities are invasion hotspots, the view of urban residents on non-native species is critically understudied – an important knowledge gap since strategies on biological invasions could gain power by integrating human values, attitudes and perceptions. How citizens perceive the non-native tree Ailanthus altissima (tree of heaven) is unknown despite its abundance in many cities globally and its classification as invasive in many countries. In a quantitative survey with closed questions, we analysed (i) whether residents of Berlin, Germany knew the widespread species, (ii) how they perceived it in different urban situations, (iii) how they accepted different management strategies of it, and (iv) how the sociodemographic background of respondents predicted their preference and acceptability ratings. In total, we surveyed 196 respondents. Most respondents recognized the tree in a photograph, but few provided its correct name. Citizens’ preferences differed significantly among four urban contexts in which the species was shown, with prevailing approval for trees as a component of designed green spaces and less pronounced preferences for wild-grown trees in other urban spaces. When respondents were asked to indicate how the tree should be managed (three options), we found the most support for removal in problematic cases (‘adaptive on-site’ strategy); some support was found for the ‘leave alone’ strategy and least support for the ‘complete removal’ management strategy. Practitioners with expertise in urban landscaping were more critical of Ailanthus than laypeople. Ordinal logistic regression analyses showed that respondents with a ‘close to nature’ behaviour and attitude had a more positive view on Ailanthus and expressed more support for ‘leave alone’ management. Results demonstrate the importance of citizens’ context dependent views about a widespread invasive species, spanning from approval to disapproval in different situations. We conclude that urban management strategies concerning Ailanthus would gain support from citizens when combining multiple approaches: (i) to control the species in case of realized negative impacts; (ii) to prevent the invasion of the species in areas of conservation concern; and (iii) to develop novel approaches of integrating wild Ailanthus trees into urban green spaces. These insights could support management measures that need to be established due to the EU-Regulation on Invasive Alien Species
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biological flora of central europe Ailanthus altissima mill swingle
Perspectives in Plant Ecology Evolution and Systematics, 2007Co-Authors: Ingo Kowarik, Ina SaumelAbstract:Abstract Ailanthus altissima (tree of heaven), Simaroubaceae, is an early successional tree, native to China and North Vietnam, which has become invasive in Europe and on all other continents except Antarctica. It is most abundant in urban habitats and along transportation corridors, but can also invade natural habitats. This paper reviews the literature on the morphology, distribution, ecology, habitat requirements, population biology, genetics, physiology, impacts, management and uses of this species.
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Clonal growth in Ailanthus altissima on a natural site in West Virginia
Journal of Vegetation Science, 1995Co-Authors: Ingo KowarikAbstract:The exotic tree Ailanthus altissima is usually con- fined to open sites. As an exception, Ailanthus established in a densely closed forest in West Virginia, which was analyzed with the aim to elucidate possible pathways of persistence in forest succession of this light-demanding pioneer species. Demographic analysis revealed a seedling mortality of 100 %. Instead, the understory is populated by clonal ramets, ranging from one to more than 19 yr of age, with a mean of 5 yr. Growth averages only 0.11 m/yr, and height is correlated with age. This clonal growth contrasts with the performance of Ailanthus on open sites. The possible ecological benefits of establishing a ramet bank in a resource-poor habitat are con- sidered in terms of space occupation of a pioneer species.
J Rebbeck - One of the best experts on this subject based on the ideXlab platform.
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first report of verticillium wilt caused by verticillium nonalfalfae on tree of heaven Ailanthus altissima in ohio
Plant Disease, 2013Co-Authors: J Rebbeck, Matthew T Kasson, E S Oneal, M A Malone, Dylan P G Short, Donald D DavisAbstract:Verticillium wilt of the highly invasive tree-of-heaven [Ailanthus altissima (Mill.) Swingle], caused by Verticillium nonalfalfae Interbitzin et al. (1), formerly classified as V. albo-atrum Reinke and Berthold, has been reported in the United States from two states: Pennsylvania (2) and Virginia (3). Infected A. altissima in both states exhibited similar symptoms of wilt, premature defoliation, terminal dieback, yellow vascular discoloration, and mortality. In June 2012, the second author observed dead and dying A. altissima trees in southern Ohio (Pike County) that exhibited symptoms similar to those on diseased A. altissima trees in Pennsylvania and Virginia. Samples were collected from stems of three symptomatic A. altissima trees and sent to Penn State for morphological and molecular identification. Immediately upon arrival, samples were surface-disinfected and plated onto plum extract agar (PEA), a semi-selective medium for Verticillium spp., amended with neomycin and streptomycin (2). The samples yielded six isolates, two from each of the three symptomatic trees, all of which were putatively identified as V. nonalfalfae based on the presence of verticillate conidiophores and formation of melanized hyphae. DNA was extracted from three isolates and molecular analyses performed using known primers (1) coding for elongation factor 1-alpha (EF), glyceraldehyde-3-phosphate dehydrogenase (GPD), and tryptophan synthase (TS). A BLAST search generated sequences that revealed 100% similarity to V. nonalfalfae for all three protein coding genes among the three Ohio isolates and reference sequences from Ailanthus, including isolates VnAaPA140 (GenBank Accession Nos. KC307764, KC307766, and KC307768) and VnAaVA2 (KC307758, KC307759, and KC307760), as well as isolate PD592 from potato (JN188227, JN188163, and JN188035), thereby confirming taxonomic placement of the Ohio Ailanthus isolates among those recovered from Ailanthus in Pennsylvania and Virginia. Aligned sequences from one representative isolate, VnAaOH1, were deposited into GenBank as accessions KC307761 (EF), KC307762 (GPD), and KC307763 (TS). In August 2012, the pathogenicity of all six isolates was confirmed by root-dipping 10 healthy 3-week-old A. altissima seedlings (seeds collected in University Park, PA) into conidial suspensions of 1 × 107 cfu/ml, wherein all inoculated seedlings wilted and died within 4 and 9 weeks, respectively. V. nonalfalfae was reisolated from all inoculated seedlings; control seedlings inoculated with distilled water remained asymptomatic. Ohio is the third state from which V. nonalfalfae has been reported to be pathogenic on A. altissima. If V. nonalfalfae proves to be widespread, it may represent a natural biocontrol for the invasive A. altissima. Also, since USDA APHIS evaluates and regulates new potential biocontrol agents on a state-by-state basis, it is important to document each state in which V. nonalfalfae is killing A. altissima, so that in-state inoculum can be used for biocontrol efforts, simplifying the regulatory process. References: (1) P. Inderbitzin et al. 2011 PLoS ONE, 6, e28341, 2011. (2) M. J. Schall and D. D. Davis. Plant Dis. 93:747, 2009. (3) A. L. Snyder et al. Plant Dis. 96:837, 2013.