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Martín JA, Domínguez J, Solla A, Brasier CM, Webber JF, Santini A, Martínez-Arias C, Bernier L, Gil L. Complexities underlying the breeding and deployment of Dutch elm disease resistant elms. NEW FORESTS 2021; 54:661-696. [PMID: 37361260 PMCID: PMC10287581 DOI: 10.1007/s11056-021-09865-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 07/03/2021] [Indexed: 06/28/2023]
Abstract
Dutch elm disease (DED) is a vascular wilt disease caused by the pathogens Ophiostoma ulmi and Ophiostoma novo-ulmi with multiple ecological phases including pathogenic (xylem), saprotrophic (bark) and vector (beetle flight and beetle feeding wound) phases. Due to the two DED pandemics during the twentieth century the use of elms in landscape and forest restoration has declined significantly. However new initiatives for elm breeding and restoration are now underway in Europe and North America. Here we discuss complexities in the DED 'system' that can lead to unintended consequences during elm breeding and some of the wider options for obtaining durability or 'field resistance' in released material, including (1) the phenotypic plasticity of disease levels in resistant cultivars infected by O. novo-ulmi; (2) shortcomings in test methods when selecting for resistance; (3) the implications of rapid evolutionary changes in current O. novo-ulmi populations for the choice of pathogen inoculum when screening; (4) the possibility of using active resistance to the pathogen in the beetle feeding wound, and low attractiveness of elm cultivars to feeding beetles, in addition to resistance in the xylem; (5) the risk that genes from susceptible and exotic elms be introgressed into resistant cultivars; (6) risks posed by unintentional changes in the host microbiome; and (7) the biosecurity risks posed by resistant elm deployment. In addition, attention needs to be paid to the disease pressures within which resistant elms will be released. In the future, biotechnology may further enhance our understanding of the various resistance processes in elms and our potential to deploy trees with highly durable resistance in elm restoration. Hopefully the different elm resistance processes will prove to be largely under durable, additive, multigenic control. Elm breeding programmes cannot afford to get into the host-pathogen arms races that characterise some agricultural host-pathogen systems.
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Affiliation(s)
- Juan A. Martín
- Departamento de Sistemas y Recursos Naturales, ETSI Montes, Forestal y del Medio Natural, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
- Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences (SLU), Alnarp, Sweden
| | - Jorge Domínguez
- Departamento de Sistemas y Recursos Naturales, ETSI Montes, Forestal y del Medio Natural, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
- Centro Nacional de Recursos Genéticos Forestales Puerta de Hierro. TRAGSA., Ctra. de la Coruña, Km 7.5, 28040 Madrid, Spain
| | - Alejandro Solla
- Faculty of Forestry, Institute for Dehesa Research (INDEHESA), University of Extremadura, Avenida Virgen del Puerto 2, 10600 Plasencia, Spain
| | | | | | - Alberto Santini
- Istituto per la Protezione Sostenibile delle Piante – C.N.R., Via Madonna del Piano, 10, 50019 Sesto Fiorentino, Italy
| | - Clara Martínez-Arias
- Departamento de Sistemas y Recursos Naturales, ETSI Montes, Forestal y del Medio Natural, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
| | - Louis Bernier
- Centre d’étude de la Forêt (CEF), Université Laval, Quebec City, QC G1V 0A6 Canada
| | - Luis Gil
- Departamento de Sistemas y Recursos Naturales, ETSI Montes, Forestal y del Medio Natural, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
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Brasier C, Franceschini S, Forster J, Kirk S. Enhanced Outcrossing, Directional Selection and Transgressive Segregation Drive Evolution of Novel Phenotypes in Hybrid Swarms of the Dutch Elm Disease Pathogen Ophiostoma novo-ulmi. J Fungi (Basel) 2021; 7:jof7060452. [PMID: 34204036 PMCID: PMC8228177 DOI: 10.3390/jof7060452] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 11/16/2022] Open
Abstract
In the 1970s, clones of the two subspecies of Ophiostoma novo-ulmi, subsp. americana (SSAM) and subsp. novo-ulmi (SSNU) began to overlap in Europe, resulting in hybrid swarms. By 1983-1986, hybrids with high, SSAM-like growth and pathogenic fitness comprised ~75% of popula-tions at Limburg, Netherlands and Orvieto, Italy. We resampled these populations in 2008 to examine trends in hybrid fitness traits. Since preliminary sampling in 1979-1980, MAT-1 locus frequency had increased from ~0% to ~32% at Orvieto and 5% to ~43% at Limburg, and vegeta-tive incompatibility type frequency had changed from near clonal to extremely diverse at both sites. This represents an enormous increase in outcrossing and recombination potential, due in part to selective acquisition (under virus pressure) of MAT-1 and vic loci from the resident O. ulmi and in part to SSAM × SSNU hybridisation. Overt virus infection in the 2008 samples was low (~4%), diagnostic SSAM and SSNU cu and col1 loci were recombinant, and no isolates exhib-ited a parental SSAM or SSNU colony pattern. At both sites, mean growth rate and mean patho-genicity to 3-5 m clonal elm were high SSAM-like, indicating sustained directional selection for these characters, though at Orvieto growth rate was slower. The once frequent SSNU-specific up-mut colony dimorphism was largely eliminated at both sites. Perithecia formed by Limburg isolates were mainly an extreme, long-necked SSNU-like form, consistent with transgressive segregation resulting from mismatch of SSAM and SSNU developmental loci. Orvieto isolates produced more parental-like perithecia, suggesting the extreme phenotypes may have been se-lected against. The novel phenotypes in the swarms are remodelling O. novo-ulmi in Europe. Locally adapted genotypes may emerge.
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Temple B, Horgen PA. Biological roles for cerato-ulmin, a hydrophobin secreted by the elm pathogens,Ophiostoma ulmiandO. novo-ulmi. Mycologia 2019. [DOI: 10.1080/00275514.2000.12061123] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Bradley Temple
- Department of Biology, University of Victoria, P.O. Box 1700, Victoria, British Columbia, V9W 2Y2 Canada
| | - Paul A. Horgen
- Department of Botany, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6 Canada
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Fourie A, Wingfield MJ, Wingfield BD, van der Nest MA, Loots MT, Barnes I. Inheritance of phenotypic traits in the progeny of a Ceratocystis interspecific cross. Fungal Biol 2018; 122:717-729. [PMID: 29880206 DOI: 10.1016/j.funbio.2018.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 03/01/2018] [Accepted: 03/02/2018] [Indexed: 12/14/2022]
Abstract
Ceratocystis fimbriata is a fungal plant pathogen that causes black rot on Ipomoea batatas. Based on inoculation studies on numerous tree species, the pathogen is known to be host specific. The closely related species, Ceratocystis manginecans, causes severe wilt on a broad range of tree hosts, including Mangifera indica, Acacia mangium and other leguminous tree species. The genetic factors underlying the pathogenicity and host specificity of Ceratocystis species have rarely been investigated. In this study, an F1 population of 70 recombinant progeny from a cross between C. fimbriata and C. manginecans was generated and the inheritance of various phenotypic traits was investigated. Results showed that colony colour, growth rate, asexual spore production and aggressiveness to I. batatas and A. mangium are all quantitative traits with high levels of heritability. However, conidia production and aggressiveness appeared to be regulated by a small number of genes. No correlation could be found between aggressiveness and other phenotypic traits, suggesting that these are inherited independently. This is the first study to consider genetic inheritance of pathogenicity and host specificity in Ceratocystis species and the results will contribute, in future, to the identification of quantitative trait loci and candidate genes associated with the traits investigated.
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Affiliation(s)
- Arista Fourie
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - Michael J Wingfield
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - Brenda D Wingfield
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - Magriet A van der Nest
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - M Theodor Loots
- Department of Statistics, University of Pretoria, Pretoria, 0002, South Africa
| | - Irene Barnes
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa.
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Hintz WE, Carneiro JS, Kassatenko I, Varga A, James D. Two novel mitoviruses from a Canadian isolate of the Dutch elm pathogen Ophiostoma novo-ulmi (93-1224). Virol J 2013; 10:252. [PMID: 23924036 PMCID: PMC3750502 DOI: 10.1186/1743-422x-10-252] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 08/07/2013] [Indexed: 11/10/2022] Open
Abstract
Background Ophiostoma novo-ulmi is the causative agent of Dutch elm disease (DED). It is an ascomycetous filamentous fungus that ranks as the third most devastating fungal pathogen in Canada. The disease front has spread eastward and westward from the epicentre in Ontario and Quebec and is threatening elm populations across the country. Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited. An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi. Methods Using a modified single primer amplification technique (SPAT) in combination with chromosomal walking, we have determined the genome sequence of two RdRp encoding dsRNA viruses from an O. novo-ulmi isolate (93–1224) collected from the disease front in Winnipeg. Results We propose that these viruses, which we have named OnuMV1c and OnuMV7 based on sequence similarity to other Ophiostoma mitoviruses, are two new members of the genus Mitovirus in the family Narnaviridae. Conclusions The discovery of such dsRNA elements raises the potential for engineering these viruses to include other genetic elements, such as anti-sense or interfering RNAs, to create novel and highly specific biological controls. Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.
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Affiliation(s)
- William E Hintz
- Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, BC V8W 3N5, Canada.
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Plourde KV, Jacobi V, Bernier L. Use of insertional mutagenesis to tag putative parasitic fitness genes in the Dutch elm disease fungus Ophiostoma novo-ulmi subsp. novo-ulmi. Can J Microbiol 2008; 54:797-802. [PMID: 18772944 DOI: 10.1139/w08-068] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used insertional mutagenesis to produce genetically tagged mutants of the Dutch elm disease fungus Ophiostoma novo-ulmi subsp. novo-ulmi. We first optimized transformation of O. novo-ulmi protoplasts by the restriction enzyme mediated integration method. A concentration of 80 U of HindIII with 108 fungal protoplasts and 5 microg of plasmid DNA was the most efficient for generating a high number of O. novo-ulmi mutants carrying a single insertion in their genome. Mycelium- and yeast-like growth kinetics of 24 O. novo-ulmi mutants were evaluated in vitro. Flanking sequences were successfully recovered in 8% of the transformants analyzed. Some mutant phenotypes appeared to result from gene disruption events, whereas others likely involved modifications of noncoding regions. Several nuclear loci that control vegetative growth and could potentially impact parasitic fitness were successfully tagged.
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Affiliation(s)
- Karine V Plourde
- Centre d'Etude de la Forêt, Faculté de Foresterie et de Géomatique, Université Laval, Québec, QCG1V0A6, Canada.
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Friel CJ, Desjardins AE, Kirkpatrick SC, Gordon TR. Evidence for recombination and segregation of virulence to pine in a hybrid cross between Gibberella circinata and G. subglutinans. ACTA ACUST UNITED AC 2007; 111:827-31. [PMID: 17681226 DOI: 10.1016/j.mycres.2007.05.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2006] [Revised: 02/27/2007] [Accepted: 05/17/2007] [Indexed: 10/23/2022]
Abstract
Two species associated with the Gibberella fujikuroi species complex, G. circinata (the cause of pitch canker in pines) and G. subglutinans (avirulent on pine), were found to have limited interfertility in hybrid crosses. MAT idiomorphs, polymorphisms in the histone H3 gene, vegetative compatibility, and virulence phenotypes were used to verify recombination. The MAT idiomorphs appeared to be assorting independently, but the histone H3 haplotype was disproportionately represented by that of the G. subglutinans parent. Ninety-eight percent (45/46) of the progeny tested were vegetatively incompatible with both parents. All F(1) progeny were avirulent to pine, but a wide range of virulence was restored through a backcross to the virulent parent (G. circinata). Attempts at hybrid crosses using other isolate combinations were rarely successful (1/26). This limited interfertility supports retention of G. circinata and G. subglutinans as separate species, but offers opportunities to characterize the inheritance of virulence to pine.
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Paoletti M, Buck KW, Brasier CM. Selective acquisition of novel mating type and vegetative incompatibility genes via interspecies gene transfer in the globally invading eukaryote Ophiostoma novo-ulmi. Mol Ecol 2006; 15:249-62. [PMID: 16367844 DOI: 10.1111/j.1365-294x.2005.02728.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The Dutch elm disease fungus Ophiostoma novo-ulmi, which has destroyed billions of elm trees worldwide, originally invaded Europe as a series of clonal populations with a single mating type (MAT-2) and a single vegetative incompatibility (vic) type. The populations then rapidly became diverse with the appearance of the MAT-1 type and many vegetative incompatibility types. Here, we have investigated the mechanism using isolates from sites in Portugal at which the rapid evolution of O. novo-ulmi populations from clonality to heterogeneity was well established. We show by genetic mapping of vic and MAT loci with AFLP markers and by sequence analysis of MAT loci that this diversification was due to selective acquisition by O. novo-ulmi of the MAT-1 and vic loci from another species, Ophiostoma ulmi. A global survey showed that interspecies transfer of the MAT-1 locus occurred on many occasions as O. novo-ulmi spread across the world. We discuss the possibility that fixation of the MAT-1 and vic loci occurred in response to spread of deleterious viruses in the originally clonal populations. The process demonstrates the potential of interspecies gene transfer for facilitating rapid adaptation of invasive organisms to a new environment.
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Affiliation(s)
- Mathieu Paoletti
- Department of Biological Sciences, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, UK
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Abstract
The objective of this review is to provide a synthesis of speciation theory, of what is known about mechanisms of speciation in fungi and from this, what is expected, and of ideas on how speciation can be elucidated in more fungal systems. The emphasis is on process rather than pattern. Phylogeographic studies in some groups, such as the agarics, demonstrate predominantly allopatric speciation, often through vicariance, as seen in many plants and animals. The variety of life history factors in fungi suggests, however, a diversity in speciation mechanisms that is borne out in comparison of some key examples. Life history features in fungi with a bearing on speciation include genetic mechanisms for intra- and interspecies interactions, haploidy as monokaryons, dikaryons, or coenocytes, distinctive types of propagules with distinctive modes of dispersal, as well as characteristic relationships to the substrate or host as specialized or generalist saprotrophs, parasites or mutualists with associated opportunities and selective pressures for hybridization. Approaches are proposed for both retrospective, phylogeographic determination of speciation mechanisms, and experimental studies with the potential for genomic applications, particularly in examining the relationship between adaptation and reproductive isolation.
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Affiliation(s)
- Linda M Kohn
- Department of Botany, University of Toronto, Mississauga, Ontario, Canada L5L 1C6.
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Harrington TC, McNew DL. Partial interfertility among the ceratocystis species on conifers. Fungal Genet Biol 1998; 25:44-53. [PMID: 9806805 DOI: 10.1006/fgbi.1998.1083] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Interspecific pairings between MAT-1 and MAT-2 strains of seven species of Ceratocystis from conifer hosts resulted in partial interfertility in many cases. Perithecia from such crosses typically produced few ascospores, which were often misshapen and intermixed with cellular debris, and a low ascospore germination percentage was seen. Intraspecific pairings of strains of opposite mating type generally produced many perithecia with many ascospores of a high germination percentage. Mycelial morphology, cycloheximide resistance, and isozyme markers were used to confirm that many of the interspecific pairings produced viable hybrid progeny. Tester strains of C. pinicola, C. coerulescens, and C. laricicola frequently crossed with other species. Because MAT-2 strains of the Ceratocystis species studied are capable of selfing due to unidirectional mating-type switching, MAT-2 tester strains that fruited poorly or were self-sterile had to be selected. In a few cases, these MAT-2 strains were induced to self by pairing with MAT-1 or MAT-2 strains of other species. Hybrids yielding ascospores formed only in crosses of strains of opposite mating type, but many interspecific pairings of strains of the same or opposite mating type resulted in the production of sterile perithecia. Partial interfertility between species based on a low number of misshapen ascospores was a good indicator of biological species, and such delineations corresponded well with species delimited by morphological and physiological phenotypes. Copyright 1998 Academic Press.
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Affiliation(s)
- TC Harrington
- Department of Plant Pathology, Iowa State University, Ames, Iowa, 50011, USA
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Rare interspecific hybrids in natural populations of the Dutch elm disease pathogens Ophiostoma ulmi and O. novo-ulmi. ACTA ACUST UNITED AC 1998. [DOI: 10.1017/s0953756297004541] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Binz T, Canevascini G. Differential production of extracellular laccase in the Dutch elm disease pathogens Ophiostoma ulmi and O. novo-ulmi. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0953-7562(96)80213-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Brasier CM. Episodic selection as a force in fungal microevolution, with special reference to clonal speciation and hybrid introgression. ACTA ACUST UNITED AC 1995. [DOI: 10.1139/b95-381] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Episodic selection encompasses any sudden environmental disturbance likely to lead to a significant alteration in a species' population structure. Such disturbances include geographical transposition, a change in substrate availability, exposure to a new host or a new vector, climate change, and pollution stress. Today, such events may often be brought about by man. Their role in the promotion of fungal microevolution is discussed. In some circumstances, episodic selection may result in the emergence of a highly fitted clone from an originally heterogeneous population, and sustained disturbance may lead to clonal speciation. Clonal speciation accompanied by loss of sexual function, whether under episodic selection or under less intensive but analagous environmental conditions, could account for the origin of many of today's imperfect taxa (Deuteromycotina). Geographical transposition, a special form of episodic selection, can lead to hybridization between previously allopatric species. This may result in modifications to existing species via the acquisition of new loci or cytoplasmic elements, in the production of new taxa via secondary speciation, or in the emergence of hybrid swarms. Episodic selection will also favour survival of novel genotypes by providing new habitats for exploitation, so encouraging novel evolutionary development. Key words: episodic selection, fungal speciation, hybridization, introgression.
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Brasier C, Kirk SA, Tegli S. Naturally occurring non cerato-ulmin producing mutants of Ophiostoma novo-ulmi are pathogenic but lack aerial mycelium. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0953-7562(09)80641-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Brasier C, Mehrotra M. Ophiostoma himal-ulmi sp. nov., a new species of Dutch elm disease fungus endemic to the Himalayas. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0953-7562(09)80887-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Bernier L, Hubbes M. Induction and genetic characterization of ultraviolet-sensitive mutants in the elm tree pathogen Ophiostoma ulmi (sensu lato). ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s0953-7562(09)80268-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Tegli S, Comparini C, Giannetti C, Scala A. Effect of temperature on growth and cerato-ulmin production of Ophiostoma novo-ulmi and O. ulmi. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s0953-7562(09)81197-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Ophiostoma novo-ulmi sp. nov., causative agent of current Dutch elm disease pandemics. Mycopathologia 1991. [DOI: 10.1007/bf00462219] [Citation(s) in RCA: 178] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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