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United States Department of Agriculture

Agricultural Research Service

Research Project: COMPARATIVE GENOMIC SYSTEMS FOR MOLECULAR DETECTION AND CONTROL OF TOXIGENIC FUSARIUM

Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: The Fusarium graminearum species complex comprises at least 16 phylogenetically distinct head blight pathogens

Authors
item Aoki, Takayuki -
item Ward, Todd
item Kistler, H
item O`donnell, Kerry

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2012
Publication Date: March 30, 2012
Citation: Aoki, T., Ward, T.J., Kistler, H.C., O Donnell, K. 2012. The Fusarium graminearum species complex comprises at least 16 phylogenetically distinct head blight pathogens. Meeting Abstract.

Technical Abstract: Fusarium head blight (FHB) or scab of cereals is one of the most economically devastating plant diseases in the world today. FHB outbreaks and epidemics of wheat and barley cause significant reduction in yields; these pathogens also frequently contaminate grain with deoxynivalenol or nivalenol trichothecene mycotoxins and estrogenic compounds, rendering it unsuitable for food or feed. Prior to 2000, the primary etiological agent of FHB was thought to comprise a single panmictic species, F. graminearum. However, a series of comparative morphological and molecular phylogenetic studies over the past decade, employing Fusarium head blight (FHB) or scab of cereals is one of the most economically devastating plant diseases in the world today. FHB outbreaks and epidemics of wheat and barley cause significant reduction in yields; these pathogens also frequently contaminate grain with deoxynivalenol or nivalenol trichothecene mycotoxins and estrogenic compounds, rendering it unsuitable for food or feed. Prior to 2000, the primary etiological agent of FHB was thought to comprise a single panmictic species, F. graminearum. However, a series of comparative morphological and molecular phylogenetic studies over the past decade, employing genealogical concordance/discordance phylogenetic species recognition (GCPSR), demonstrated that this morphospecies comprises at least 16 phylogenetically distinct species. These species form a genealogically exclusive clade designated the F. graminearum species complex (FGSC). GCPSR-based phylogenetic analyses were conducted on DNA sequences from portions of 12 genes comprising 16.3 kb of aligned DNA sequence data. Morphological species recognition (MSR) was based on detailed analyses of conidial morphology, including sizes, widest position, rate of curvature and possession of a narrow apical beak, together with growth rate and colony morphology on PDA. Due to their morphological simplicity, MSR only resolved 6 species and 3 species groups within the FGSC. Fourteen novel species within the FGSC have been formally described, with F. graminearum sensu stricto retained as the name for the primary FHB pathogen in North America and Europe. Because most of the FGSC species exhibit significant biogeographic structure, our working hypothesis is independent allopatric species radiations may have taken place in Asia, North America, South America, Australia and possibly Africa. Of the three species that comprise a putative Asian clade, F. asiaticum has been found to be the most important FHB pathogen in Japan, Korea and China. A validated multilocus genotyping (MLGT) assay for species determination and toxin chemotype prediction has been invaluable in advancing our understanding of the distribution of FHB pathogens and their toxin potential. In addition, the MLGT was instrumental in the discovery of novel FHB pathogens within the FGSC from Japan (F. vorosii), the United States (F. gerlachii and F. louisianense), Nepal (F. nepalense), Ethiopia (F. aethiopicum), and the Far East of the Russian Federation (F. ussurianum). Because global trade in plants and plant products could easily result in the accidental geographic transposition of FHB pathogens into non-indigenous areas, our ongoing molecular surveillance is directed at obtaining a detailed, up-to-date picture of FHB species distributions and their trichothecene chemotype potential worldwide., demonstrated that this morphospecies comprises at least 16 phylogenetically distinct species. These species form a genealogically exclusive clade designated the F. graminearum species complex (FGSC). GCPSR-based phylogenetic analyses were conducted on DNA sequences from portions of 12 genes comprising 16.3 kb of aligned DNA sequence data. Morphological species recognition (MSR) was based on detailed analyses of conidial morphology, including sizes, widest position, rate of curvature and possession of a narrow apical beak, together with growth rate and colony morphology on PDA. Due to their morphological simplicity, MSR only resolved 6 species and 3 species groups within the FGSC. Fourteen novel species within the FGSC have been formally described, with F. graminearum sensu stricto retained as the name for the primary FHB pathogen in North America and Europe. Because most of the FGSC species exhibit significant biogeographic structure, our working hypothesis is independent allopatric species radiations may have taken place in Asia, North America, South America, Australia and possibly Africa. Of the three species that comprise a putative Asian clade, F. asiaticum has been found to be the most important FHB pathogen in Japan, Korea and China. A validated multilocus genotyping (MLGT) assay for species determination and toxin chemotype prediction has been invaluable in advancing our understanding of the distribution of FHB pathogens and their toxin potential. In addition, the MLGT was instrumental in the discovery of novel FHB pathogens within the FGSC from Japan (F. vorosii), the United States (F. gerlachii and F. louisianense), Nepal (F. nepalense), Ethiopia (F. aethiopicum), and the Far East of the Russian Federation (F. ussurianum). Because global trade in plants and plant products could easily result in the accidental geographic transposition of FHB pathogens into non-indigenous areas, our ongoing molecular surveillance is directed at obtaining a detailed, up-to-date picture of FHB species distributions and their trichothecene chemotype potential worldwide.

Last Modified: 8/31/2014
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