Progress 01/19/11 to 01/18/16
Outputs
Progress Report Objectives (from AD-416): The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416): Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet, 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance, and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). One of the primary goals of Objective 1 was to expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria by the global Fusarium research community. This objective was accomplished in collaboration with colleagues at the Fungal Biodiversity Centre (CBS-KNAW) Utrecht, the Netherlands, and collaborators at the Pennsylvania State University. The utility of two web-accessible sites (Fusarium MLST, http://www.cbs.knaw. nl/Fusarium; and Fusarium-ID, http://isolate.fusariumdb.org) was enhanced by depositing multilocus DNA sequence data from our pathogen genetic diversity studies in both databases, and in National Center for Biotechnology Information (NCBI) (http://www.ncbi.nlm.nih.gov/) and TreeBASE (https://treebase.org/). The former two web-accessible sites are dedicated to the molecular identification of toxigenic and pathogenic Fusarium, thereby facilitating global epidemiological studies and contributing to improved disease surveillance and global monitoring of these economically important pathogens via the Internet. To provide an example of their utility, the Fusarium MLST site had 5670 unique users and was visited 9930 times and 41,487 pages were viewed during the past year. As such, Fusarium MLST and Fusarium-ID provide invaluable web-based resources needed to develop control and intervention strategies so that fusaria and their toxins do not enter the food chain. A second goal of Objective 1, to develop novel pathogen detection technologies, was accomplished in part via a collaborative study on the origin, distribution, and evolution of Fusarium graminearum strains within North America that produce a novel type A trichothecene toxin (NX toxin). Probes targeting the genetic variation responsible for NX toxin-producing strains were developed and integrated into a published multilocus genotyping (MLGT) assay for rapid detection and identification of F. graminearum strains with the ability to produce NX toxin. The MLGT molecular diagnostic assay was also expanded to include probes for the rapid and accurate identification of two novel nivalenol trichothecene toxin-producing Fusarium head blight pathogens, F. dactylidis and F. praegraminearum. Based on analyses of whole genome sequence data, which suggested that these two pathogens might produce the trichothecene toxin nivalenol, mycotoxin analyses were conducted that demonstrated they could produce nivalenol in planta and in solid and liquid cultures, as well as the estrogenic mycotoxin zearalenone in vitro. In joint research with agricultural scientists in Australia and Japan, genetic and genomic analyses were conducted on a novel bikaverin and fusarubin toxin- producing Fusarium pathogen from Italy and Australia. As predicted by the whole genome sequence data, mycotoxin analyses revealed that this pathogen could produce bikaverin and fusarubin toxins in vitro. The genomic analyses also established that this pathogen only possessed part of the biosynthetic toxin gene clusters needed to produce enniatin, equisetin, and fumonisin toxins. As predicted by the whole genome sequence data, chemical analyses of solid cultures of this novel pathogen failed to detect enniatin, equisetin, and fumonisin toxins. A third goal of Objective 1, to characterize the mycotoxin potential and genetic diversity of fusarial pathogens was accomplished by developing a robust genealogy of Fusarium inferred from portions of two genes, providing a detailed picture of evolutionary relationships and phylogenetic diversity within this economically important and systematically challenging group of fungi. These analyses revealed that Fusarium comprises 22 strongly supported genealogically exclusive species complexes and seven single- pathogen lineages. Furthermore, analysis of Fusarium genome sequence data and molecular genetic data elucidated the distribution of genes required for synthesis of 26 families of secondary metabolites, thereby providing a framework for future comparative phylogenetic and genomic analyses of this agronomically and medically important genus. In a collaborative study with a genome biologist at the University of California-Riverside, 71 phylogenetically informative genes were mined from low coverage genome sequence data from 93 fusaria. The genealogy inferred from this comparative genomic data provided a nearly fully resolved phylogenetic hypothesis that supported a single evolutionary origin of Fusarium. The primary goal of Objective 2 was to determine the global population structure of F. graminearum and improve understanding of diversity among Fusarium head blight (FHB) pathogens. Molecular marker and genome sequence data were used to assess population structure, diversity and toxin production capacity. Results demonstrated that FHB pathogen and toxin diversity in North America is shaped by regional differences and does not reflect a simple model of dispersal and integration following the introduction of an invasive pathogen population. Specifically, an invasive population of F. graminearum, in which the 3ADON toxin type predominates, has largely replaced the native pathogen populations in parts of the Upper Midwest and Canada over the last two decades. However, this population has enjoyed limited success in wheat fields from other regions; including the northeastern U.S. Admixture between the invasive and native populations was documented, indicating the potential for exchange of adaptations. However, significant regional differences in the rate and direction of gene flow between genetic populations were also documented. Expanding these analyses to a global collection of more than 2,700 F. graminearum isolates revealed that the invasive population in North America was likely introduced from eastern Asia and is most closely related to populations in East Asia. The introduced population has signatures of a recent genetic bottleneck, consistent with recent transcontinental migration and is far less diverse than its source populations in Asia and the native population in North America. Overall, genetic diversity within F. graminearum is very high and is partitioned into three genetic subgroups that appear to have originated in Asia, Europe, and North America. The native population in North America represents a genetic outlier that is largely distinct from populations found throughout much of the rest of the world. This suggests that cereals in North America have been exposed to a relatively small and distinct segment of F. graminearum diversity found globally, such that introductions of non-native pathogens have the potential to further exacerbate problems associated with FHB and related cereal diseases. These results and the molecular methods developed to differentiate, identify, and track pathogen populations from around the world should inform plant breeding efforts and the development of other disease control measures aimed at improving crop production and preventing mycotoxin contamination of grain. Molecular surveillance and characterization of FHB pathogen composition and toxin diversity beyond F. graminearum was also conducted by developing a broad international collaboration. Although species and toxin diversity was biogeographically structured, the results provided evidence of significant host specialization among FHB pathogen and toxin types. F. graminearum with the 15ADON toxin type often predominated on wheat collected from around the world, whereas species such as F. asiaticum and F. meridionale with the nivalenol toxin type appeared to be adapted to corn and rice agroecosystems. These results document the potential for significant differences in toxin exposure risks based on the relative prevalence of different cereals in local diets, and inform testing programs and public health officials about the need for monitoring of specific toxins in different regions and in different commodities. Differences in species and toxin type composition among FHB isolates were also significantly associated with ecological factors such as temperature, indicating that changes in climate may be expected to result in changes in the composition of FHB pathogens and toxin types in a particular region. Molecular surveillance and toxin analyses conducted in collaboration with ARS scientists in St. Paul, Minnesota, resulted in the identification of strains of F. graminearum from the Upper Midwest of the United States that produce two previously unknown trichothecene toxins, termed NX toxins. The chemical structure of these novel toxins was determined and methods for identifying these previously masked mycotoxins were developed. Accomplishments 01 Discovery and characterization of a novel nivalenol toxin-producing Fusarium head blight (FHB) pathogen. Fungal pathogens within the B group of trichothecene toxin-producing fusaria are the primary causal agents of FHB world-wide. In a collaborative study with scientists in Canada and New Zealand, ARS scientists in Peoria, Illinois, discovered and characterized a novel FHB pathogen from New Zealand. Toxin analyses revealed that this novel pathogen could produce nivalenol toxin in wheat and in solid and liquid cultures, and induce head blight on wheat. This pathogen was also able to produce zearalenone, which is an estrogenic reproductive toxin. A multilocus genotyping assay for species determination and trichothecene toxin potential was expanded to include probes for the rapid and accurate identification of this novel toxin-producing pathogen. Through improved molecular diagnostic detection and identification of this novel nivalenol toxin-producing FHB pathogen, results of this study help promote food safety and food security. In addition, knowledge of FHB pathogen diversity advances plant quarantine efforts directed at preventing exotic pathogens from entering the U.S. 02 A simple how-to guide to efficiently use three web-accessible reference databases to identify pathogenic and toxin-producing Fusarium isolates. Fusarium ranks as one of the world�s most economically destructive and species-rich groups of toxigenic plant pathogens. In most cases, isolates can only be accurately identified to the species level by using DNA sequence data from one or more informative genes to query a reference database. Thus, ARS scientists in Peoria, Illinois, together with colleagues in the Netherlands prepared this mini-review which provides a contemporary guide to the following three web-accessible resources for DNA sequence-based identification of Fusarium: FUSARIUM- ID (http://isolate.fusariumdb.org/), Fusarium MLST (http://www.cbs.knaw. nl/fusarium/), and NCBI GenBank (http://www.ncbi.nlm.nih.gov/). To help orient end-users who are unfamiliar with this genus, the systematics and genetic diversity of the group are reviewed briefly together with how genealogically distinct species are delimited using multilocus DNA sequence data. The review provides a detailed flowchart outlining 10 steps that are recommended to increase the likelihood of obtaining an accurate DNA sequence-based species- or species complex-level identification of an unknown Fusarium. These databases are continuously populated with new sequences as novel toxigenic Fusarium pathogens are discovered and characterized genetically, thereby increasing their utility to the scientific community. Information provided in this review promotes agricultural food security, food safety, and supports plant quarantine efforts to prevent exotic Fusarium pathogens from entering the U.S. 03 The risk from invasive or novel Fusarium head blight pathogens and toxin types varies by region and host. Fusarium graminearum is a fungus that causes Fusarium head blight (FHB) in cereal crops and contaminates grain with mycotoxins such as deoxynivalenol (DON) that pose a significant threat to food safety and animal health. ARS scientists in Peoria, Illinois, and St. Paul, Minnesota, demonstrated that an introduced FHB population has largely replaced the native pathogen populations in parts of the Upper Midwest, central Canada, and the Canadian Maritime provinces, but has enjoyed limited success in wheat fields from other regions, such as Quebec and Ontario. The invasive population has also had a limited influence on FHB pathogen composition and mycotoxin contamination in wheat fields sampled from Indiana and Kentucky, and was more prevalent on wheat than on barley in the Upper Midwest. Significant regional differences in the rate and nature of genetic exchange between the introduced and native pathogen populations were also documented. In addition, F. graminearum strains that produce the novel trichothecene toxin NX-2 were identified for the first time in Canadian wheat, representing a significant expansion of the known range of NX-2 producing strains in North America. The results demonstrate that FHB pathogen and toxin diversity in North America is shaped by regional differences and does not reflect a simple model of dispersal and integration following the introduction of an invasive pathogen population. In addition, these findings provide the information needed to account for population-level variation in disease management and toxin control programs, and emphasize the need for a regional approach to FHB and mycotoxin management. 04 The risk of nivalenol contamination is shaped by host preference. Fungi within the Fusarium graminearum species complex (FGSC) are responsible for Fusarium head blight (FHB) of wheat, Fusarium ear rot (FER) of corn, and economically destructive diseases of other cereals world-wide. These fungi also contaminate grain with trichothecene mycotoxins that pose a significant threat to food safety and animal health. ARS scientists in Peoria, Illinois, in collaboration with scientists in Brazil determined the prevalence of FGSC species and toxin types associated with corn in Brazil. F. meridionale with the nivalenol (NIV) toxin type predominated among isolates from corn in Brazil, whereas previous studies in this same region demonstrated that F. graminearum with the deoxynivalenol (DON) toxin type and F. asiaticum with the NIV toxin type were dominant on wheat and rice, respectively. These results indicate that despite being able to incite disease on a wide variety of cereals, differences in host preference shape pathogen composition and the risk of exposure to different mycotoxins. This information provides regulatory agencies, food producers and processors, and mycotoxin scientists with information needed to develop and implement more effective mycotoxin control strategies that will ensure a safe food supply. 05 The distribution of epidemic potential among Listeria monocytogenes strains is widespread. Listeria monocytogenes (Lm) is a food-borne bacterium that can cause serious illness in humans and animals (listeriosis). Historically, strains of serotype 4b have caused most of the major listeriosis outbreaks. However in 2011, two other common serotypes, 1/2a and 1/2b, were involved in one of the largest foodborne outbreaks in United States history. ARS scientists in Peoria, Illinois, in collaboration with scientists from the Centers for Disease Control, Cornell University, and North Dakota State University used whole genome sequences to reconstruct the evolutionary relationships among Lm strains responsible for recent and historical outbreaks. Results of these analyses indicated that epidemic potential may be more widespread in Lm than previously understood. In addition, the results indicate that levels of genetic variation within individual epidemic clones can vary widely and may not be consistent with estimates of similarity derived from typing methods that are commonly employed in outbreak investigations. These findings highlight the need for increased sampling of isolates from patients and potential sources to ensure the entire diversity of strains involved in listeriosis outbreaks are identified in outbreak investigations.
Impacts
(N/A)
Publications
- Bec, S., Ward, T.J., Farman, M., O'Donnell, K., Hershman, D., Van Sanford, D., Vaillancourt, L.J. 2015. Characterization of Fusarium strains recovered from wheat with symptoms of head blight in Kentucky. Plant Disease. 99(11):1622-1632.
- Liang, J., Lofgren, L., Ma, Z., Ward, T.J., Kistler, H.C. 2015. Population subdivision of Fusarium graminearum from barley and wheat in the upper Midwestern United States at the turn of the century. Phytopathology. 105(11):1466-1474.
- Kelly, A.C., Clear, R.M., O'Donnell, K., McCormick, S., Turkington, T.K., Tekauz, A., Gilbert, J., Kistler, H.C., Busman, M., Ward, T.J. 2015. Diversity of Fusarium head blight populations and trichothecene toxin types reveals regional differences in pathogen composition and temporal dynamics. Fungal Genetics and Biology. 82:22-31.
- Kuhnem, P.R., Ward, T.J., Silva, C.N., Spolti, P., Ciliato, M.L., Tessman, D.J., Del Ponte, E.M. 2016. Composition and toxigenic potential of the Fusarium graminearum species complex from maize ears, stalks and stubble in Brazil. Plant Pathology. 65(7):1185-1191. doi: 10.1111/PPA.12497.
- O'Donnell, K., Ward, T.J., Robert, V.A.R.G., Crous, P.W., Geiser, D.M., Kang, S. 2015. DNA sequence-based identification of Fusarium: Current status and future directions. Phytoparasitica. 43(5):583-595.
- Bergholz, T.M., den Bakker, H.C., Katz, L.S., Silk, B.J., Jackson, K.A., Kucerova, Z., Joseph, L.A., Turnsek, M., Gladney, L.M., Halpin, J.L., Xavier, K., Gossack, J., Ward, T.J., Frace, M., Tarr, C.L. 2016. Determination of evolutionary relationships of outbreak-associated Listeria monocytogenes strains of serotypes 1/2a and 1/2b by whole-genome sequencing. Applied and Environmental Microbiology. 82(3):928-938.
- Pritchard, J.C., Jacob, M.E., Ward, T.J., Parsons, C.T., Kathariou, S., Wood, M.W. 2016. Listeria monocytogenes septicemia in an immunocompromised dog. Veterinary Clinical Pathology. 45(2):254-259.
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Progress 10/01/14 to 09/30/15
Outputs
Progress Report Objectives (from AD-416): The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416): Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet, 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance, and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). The origin, distribution, and evolution of a novel type A trichothecene toxin (NX toxin) was determined. Probes targeting the genetic variation responsible for the NX toxin type were developed and integrated into a published multilocus genotyping assay for rapid identification of strains with the ability to produce NX toxin. A combination of molecular surveillance and population genetic analyses were used to demonstrate significant regional differences in the composition and toxin production capacity of Fusarium head blight (FHB) pathogen populations in North America. Significant regional differences in the rate and nature of genetic exchange between introduced and native pathogen populations were demonstrated. Molecular characterization of FHB species and toxin diversity provided additional evidence of host specialization among FHB pathogen and toxin types, with different species and toxins predominating on wheat, corn, and rice. These analyses also demonstrated that the major FHB pathogen of wheat in Mexico is different than in the United States. In joint research with agricultural scientists in Japan, New Zealand, and collaborators at the Pennsylvania State University, we conducted a detailed genetic analysis of a novel FHB pathogen that we discovered within the U.S. infecting Dactylis glomerata (orchard grass), one of the world�s most important forage grasses. Mycotoxin analyses established that this novel FHB pathogen could produce the trichothecene mycotoxin nivalenol in planta as well as detectable amounts of the estrogenic mycotoxin zearalenone in vitro. Pathogenicity tests also revealed that the orchard grass isolates could induce head blight symptoms on wheat. Given the economic importance of FHB pathogens and their toxins to U.S. and global agriculture, we formally described the orchard grass pathogen as F. dactylidis to foster accurate communication of it within the scientific community. In collaborative research with fungal biologists at the Centraalbureau voor Schimmelcultures Biodiversity Center, Utrecht, The Netherlands and collaborators at the Pennsylvania State University, Pennsylvania, we increased the utility of two web-accessible sites (Fusarium multilocus sequence typing (MLST), http://www.cbs.knaw.nl/Fusarium; and Fusarium-ID, http://isolate.fusariumdb.org) by depositing multilocus DNA sequence data from our pathogen genetic diversity studies in both databases. These dedicated web-accessible sites were developed to facilitate rapid and accurate identification of toxigenic and pathogenic fusaria via the Internet. In addition, the Fusarium MLST website was updated to provide detailed instructions on how to query the database with a DNA sequence from an unknown. These two dedicated sites facilitate global epidemiological studies and contribute to improved disease surveillance and global monitoring via the Internet. In addition, the multilocus DNA sequence data deposited in Fusarium MLST and Fusarium-ID has proven to be extraordinarily useful in developing molecular surveillance technologies for monitoring the global movement of FHB and other fusarial pathogens and their toxins. The overarching goal of this research is to develop potential control and intervention strategies so that fusaria and their toxins do not enter the food chain. Accomplishments 01 The distribution of Fusarium head blight (FHB) pathogens and toxin contamination of cereals are influenced by host preference. Fungi within the Fusarium graminearum species complex (FGSC) are responsible for FHB of cereal crops world-wide. FHB significantly reduces crop yield and results in contamination of grain with trichothecene mycotoxins, such as deoxynivalenol (DON) and nivalenol (NIV), which pose a significant threat to food safety and animal health. In collaboration with scientists in Brazil, ARS scientists in Peoria, Illinois, demonstrated significant regional and crop-specific differences in FHB pathogen and toxin diversity. The results suggest that wheat is most susceptible to F. graminearum and the DON toxin type, whereas Fusarium species with the NIV toxin type predominated on rice. In addition, we demonstrated that pathogen and toxin composition was influenced by field elevation above sea level. The results indicate that rice could serve as a reservoir for FHB pathogens with the NIV toxin type, enabling these pathogens to cause disease and NIV contamination of wheat in regions where rice production is significant. These results are critical to promoting food safety through improved understanding of ecological and host-specific factors that shape FHB pathogen diversity and toxin exposure potential. 02 Detection and characterization of a novel trichothecene mycotoxin produced by Fusarium head blight (FHB) pathogens. Fusarium graminearum and related fungi are responsible for FHB and other economically destructive diseases of cereal crops world-wide. In addition, these fungi contaminate grain with mycotoxins that pose a significant threat to food safety and animal health and represent enormous losses of food and feed worldwide as well as to high costs for monitoring and mycotoxin management to protect consumers. ARS scientists in St. Paul, Minnesota, and Peoria, Illinois, in collaboration with scientists in Austria identified strains of F. graminearum from the Upper Midwest of the United States that produce a previously unknown trichothecene toxin, termed NX toxin. We determined the chemical structure of this novel toxin and described why it is not detectable by analytical methods that are widely used for mycotoxin monitoring. In addition, we demonstrated that NX toxin has nearly the same toxicity to plants and animals as deoxynivalenol (DON), which is regulated in many countries. Finally, the gene responsible for the ability to produce NX toxin was identified and a genetic test was developed to rapidly identify fungi capable of producing the novel NX toxin. These results are critical to promoting food safety and cereal production through improved mycotoxin monitoring and improved understanding of fungal diversity that can inform efforts to breed cereals with broad resistance to FHB. 03 etection of significant changes in Fusarium head blight (FHB) pathogen populations and toxin types in the Upper Midwest. Fusarium graminearum causes FHB in wheat and barley, and contaminates grains with trichothecene mycotoxins that are a significant threat to food safety and crop production. In collaboration with ARS scientists in St. Paul, Minnesota and in Peoria, Illinois, documented significant changes in the composition of FHB pathogen populations and toxin types in the Upper Midwest. Strains from a new pathogen population increased by approximately 4 fold between 1999 and 2013 and their range expanded southward toward the border between Minnesota and South Dakota. This change is a significant concern for cereal production and food safety as strains from the new population have previously been shown to grow more quickly, to be more aggressive on some lines of wheat, and to accumulate more trichothecene toxin in grain than strains from the traditional FHB population in the Upper Midwest. These results are critical to promoting food safety and cereal production through improved detection of novel FHB pathogens and toxin types, and through plant quarantine and variety improvement efforts that account for the entire spectrum of FHB pathogen and toxin type diversity. 04 Detection and characterization of a novel nivalenol toxin-producing head blight pathogen. Fungi within the B lineage of trichothecene toxin-producing fusaria are responsible for Fusarium head blight (FHB) of cereal crops world-wide. ARS scientists in Peoria, Illinois, in collaboration with scientists in Japan and New Zealand, discovered and characterized a novel FHB pathogen from Dactylis glomerata (orchard grass), one of the world�s most important forage grasses. Formally described as F. dactylidis, isolates of this novel FHB pathogen produced nivalenol mycotoxin in planta as well as low but detectable amounts of the estrogenic mycotoxin zearalenone in vitro. Results of a pathogenicity test revealed that F. dactylidis induced mild head blight on wheat. Results of this study help promote cereal production and food safety through improved detection of novel FHB pathogens and toxin types, and through plant quarantine and variety improvement efforts that account for the entire spectrum of FHB pathogen and toxin type diversity. 05 Evolution of resistance to cyanate fungicides by fungi that cause vascular wilts. Fungi within the Fusarium oxysporum species complex (FOSC) are responsible for scores of economically destructive vascular wilt diseases of vegetable and horticultural plants world-wide. The general purpose fungicide cyanate has been widely used in agriculture to control plant diseases, however some pathogens are resistant to cyanate fungicides. As part of a project to characterize the evolution of cyanate resistance, ARS scientists in Peoria, Illinois, in collaboration with scientists at Vanderbilt University and the Ohio State University, discovered a cluster of two genes responsible for cyanate degradation by vascular wilt pathogens within the FOSC. Analyses of 163 FOSC strains from a wide variety of hosts suggest that the gene cluster has been transferred between isolates, possibly in response to cyanates produced by plants and\or the use of cyanate fungicides in agriculture. These results are critical to promoting agricultural biosecurity, food safety, and informed plant breeding programs through improved understanding of the genetics of FOSC resistance to the widely used fungicide cyanate.
Impacts
(N/A)
Publications
- Liang, J., Xayamongkhon, H., Broz, K.L., Dong, Y., McCormick, S.P., Abramova, S., Ward, T.J., Ma, Z.H., Kistler, H.C. 2014. Temporal dynamics and population genetic structure of Fusarium graminearum in the upper Midwestern United States. Fungal Genetics and Biology. 73:83-92.
- Gomes, L.B., Ward, T.J., Badiale-Furlong, E., Del Ponte, E.M. 2015. Species composition, toxigenic potential and pathogenicity of Fusarium graminearum species complex isolates from southern Brazilian rice. Plant Pathology. 64(4):980-987.
- Varga, E., Wiesenberger, G., Hametner, C., Ward, T.J., Dong, Y., Schofbeck, D., McCormick, S.P., Broz, K.L., Stuckler, R., Schuhmacher, R., Krska, R., Kistler, H.C., Berthiller, F., Adam, G. 2015. New tricks of an old enemy: isolates of Fusarium graminearum produce a type A trichothecene mycotoxin. Environmental Microbiology. 17(8):2588-2600.
- Aamot, H.U., Ward, T.J., Brodal, G., Vralstad, T., Larsen, G., Klemsdal, S. S., Elameen, A., Uhlig, S., Hofgaard, I.S. 2015. Genetic and phenotypic diversity within the Fusarium graminearum species complex in Norway. European Journal of Plant Pathology. 142(3):501-519.
- Scandiani, M.M., Luque, A.G., Razori, M.V., Ciancio Casalini, L., Aoki, T., O'Donnell, K., Cervigni, G.L., Spampinato, C.P. 2015. Metabolic profiles of soybean roots during early stages of Fusarium tucumaniae infection. Journal of Experimental Botany. DOI:10.1093/jxb/eru432.
- Del Ponte, E.M., Spolti, P., Ward, T.J., Gomes, L.B., Nicolli, C.P., Kuhnem, P.R., Silva, C.N., Tessmann, D.J. 2015. Regional and field- specific factors affect the composition of Fusarium head blight pathogens in subtropical no-till wheat agroecosystem of Brazil. Phytopathology. 105(2):246-254.
- Elmore, M., McGary, K.L., Wisecaver, J.H., Slot, J.C., Geiser, D.M., Sink, S.L., O'Donnell, K., Rokas, A. 2015. Clustering of two genes involved in cyanate detoxification evolved recently and independently in multiple fungal lineages. Genome Biology and Evolution. 7(3):789-800.
- Aoki, T., Vaughan, M.M., McCormick, S.P., Busman, M., Ward, T.J., Kelly, A. C., O'Donnell, K., Johnston, P.R., Geiser, D.M. 2015. Fusarium dactylidis sp. nov., a novel nivalenol toxin-producing species sister to F. pseudograminearum isolated from orchard grass (Dactylis glomerata) in Oregon and New Zealand. Mycologia. 107(2):409-418.
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Progress 10/01/13 to 09/30/14
Outputs
Progress Report Objectives (from AD-416): The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416): Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet, 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance, and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). Fungi within the Fusarium graminearum species complex (FGSC) are responsible for Fusarium head blight (FHB) of wheat and economically destructive diseases of other cereals world-wide. These fungi also contaminate grain with trichothecene mycotoxins that pose a significant threat to food safety and animal health. As part of a project to establish a global picture of FHB pathogen diversity, ARS extended a previous analyses of population structure and diversity among F. graminearum from North America. In collaboration with scientists at the ARS Cereal Disease Laboratory, St. Paul, Minnesota, ARS completed an analysis of the temporal dynamics and population genetic structure of F. graminearum in the upper midwestern United States. FHB isolates with a novel trichothecene toxin type were characterized and comparative analyses of deoxyribonucleic acid (DNA) sequences from the gene responsible for this difference in toxin type revealed 14 conserved differences in the predicted amino acid sequences. A polymerase chain reaction (PCR) based assay for identification of strains with the novel toxin type was developed and validated, and has been used to assess the frequency and distribution of the novel toxin type across major wheat growing regions of North America and among F. graminearum isolates from Europe and Asia. Analyses of genetic and toxin type diversity were also conducted using FHB isolates from Kentucky and Indiana wheat. In addition, we further characterized the prevalence of FGSC species and toxins associated with FHB infected wheat in Brazil, and also characterized the influence of ecological factors and cropping practices on FHB pathogen and toxin composition in different regions and within individual fields. A panel of more than 50 loci were selected for phylogenetic and population genetic analyses among the FGSC, and methods were developed for high throughput determination of genetic variation at these loci using next generation sequencing platforms. These data have been collected and analyzed for all members of the FGSC as well as for multiple populations of F. graminearum from North America. Accomplishments 01 Identification of regional differences in mycotoxin prevalence among FHB pathogens. Fungi within the Fusarium graminearum species complex (FGSC) are responsible for economically destructive diseases of wheat, barley, and other cereals world-wide. In addition, these fungi contaminate grain with trichothecene mycotoxins that pose a significant threat to food safety and animal health. As part of a project to establish a global picture of FGSC diversity, ARS scientists in the Bacterial Foodborne Pathogens and Mycology Research Unit, National Center for Agricultural Utilization Research, Peoria, Illinois, determined the prevalence of FGSC species and toxins associated with diseased cereals in France. Significant regional differences in the frequencies of toxin types were observed, and F. graminearum with the nivalenol (NIV) toxin type were a significant component of the population from the south of France. This is a significant concern for food safety and animal health, because NIV is considered more toxic than the more common deoxynivalenol (DON) toxin type. In addition, a small percentage of the isolates from France were identified as species originating in the Southern hemisphere and may represent recent introductions of non-native pathogens. These results are critical to promoting food safety and cereal production through improved understanding of the distribution of Fusarium head blight (FHB) pathogen and toxin diversity and through improved detection of novel FHB pathogens and toxin types that may bring with them additional difficulties for agricultural production and food safety. 02 Understanding the factors responsible for changes in FHB pathogen populations. As has been observed in several European countries, the frequency of Fusarium head blight (FHB) caused by members of the Fusarium graminearum species complex (FGSC) has increased in Norwegian cereals in recent years, resulting in elevated levels of deoxynivalenol (DON) in cereal grains. In collaboration with Norwegian scientists, ARS scientists in the Bacterial Foodborne Pathogens and Mycology Research Unit, National Center for Agricultural Utilization Research, Peoria, Illinois, demonstrated that the increased frequency of these FHB pathogens in Norway have not been associated with significant changes in FGSC species or trichothecene toxin types, but are likely due to changes in agricultural practices and weather conditions during cereal flowering in Norway. However, isolates with the 15-ADON toxin type were detected for the first time in Norway, and the analyses indicate these isolates were recently introduced from other parts of Europe. In addition, two distinct pathogen populations that differ in aggressiveness to spring wheat were identified. These results indicate the need for careful monitoring of FHB pathogen populations and advance food safety and cereal production through improved understanding of pathogen diversity and improved understanding of the factors responsible for changes in pathogen distributions and prevalence.
Impacts
(N/A)
Publications
- Lee, S., Ward, T.J., Graves, L.M., Tarr, C., Siletzky, R.M., Kathariou, S. 2014. Population structure of Listeria monocytogenes serotype 4b isolates from sporadic human Listeriosis in the United States, 2003-2008. Applied and Environmental Microbiology. 80(12):3632-3644.
- Boutigny, A., Ward, T.J., Ballois, N., Iancu, G., Ioos, R. 2014. Diversity of the Fusarium graminearum species complex on French cereals. European Journal of Plant Pathology. 138(1):133-148.
- Ma, L., Geiser, D.M., Proctor, R.H., Rooney, A.P., O'Donnell, K., Trail, F. , Gardiner, D.M., Manners, J.M., Kazan, K. 2013. Fusarium Pathogenomics. Annual Review of Microbiology. 67:399-416.
- Aoki, T., O'Donnell, K., Geiser, D.M. 2014. Systematics of key phytopathogenic Fusarium species: current status and future challenges. Journal of General Plant Pathology. 80(3):189-201.
- Umpierrez-Failache, M., Garmendia, G., Pereyra, S., Rodriquez-Haralambides, A., Ward, T.J., Vero, S. 2013. Regional differences in species composition and toxigenic potential among Fusarium head blight isolates from Uruguay indicate a risk of nivalenol contamination in new wheat production areas. International Journal of Food Microbiology. 166(2013) :135-140.
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Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416): Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet, 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance, and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). A pilot project to identify genomic regions that could be used to assess population diversity and evolutionary relationships within and between Fusarium head blight (FHB) populations from five continents was completed. More than forty large genomic regions were sequenced across a panel of isolates representing more than 30 geographic populations, and each of these regions was analyzed to assess single nucleotide polymorphism content and phylogenetic utility. A subset of 20 regions was selected for use in population diversity analysis. These data are being used to determine the recent and potential future movement of Fusarium head blight pathogen populations and to detect introductions of invasive pathogen populations. These data will also be used to identify regions of the genome that are responsible for observed differences in growth, toxin production, and aggressiveness in order to improve disease modeling, detection, and control strategies. In addition, we completed studies of diverse FHB populations in France, Uruguay, and Brazil in order to evaluate host-preference and assess the potential threat posed by Fusarium head blight species and populations from outside the United States. Our findings indicate an increasing risk of exposure to nivalenol outside of Asia. Finally, in collaboration with scientists at the ARS Cereal Disease Laboratory, St. Paul, Minnesota, we identified genetic variation in the TRI1 trichothecene biosynthetic gene that is linked to the production of a novel trichothecene mycotoxin by Fusarium graminearum isolates in the Upper Midwest. We completed a detailed analysis of genetic diversity within the mycotoxigenic plant pathogenic genus Fusarium in collaboration with agricultural scientists in the Netherlands, Norway, Denmark, Japan, and collaborators at the Pennsylvania State University and in USDA-ARS, Beltsville, Maryland. Portions of three genes were sequenced for more than 800 Fusarium isolates to assess evolutionary relationships and to develop a robust framework for predicting mycotoxin potential. These analyses identified 20 species complexes and nine single-species lineages within Fusarium. Molecular dating of the Fusarium phylogeny indicated that the trichothecene toxin-producing pathogens responsible for Fusarium head blight of cereals, the F. oxysporum vascular wilts of over 100 economically important crops (e.g., banana, cotton, tomato), and the fumonisin toxin-producing members of the F. fujikuroi species complex appear to have evolved relatively recently. Given the economic importance of Fusarium and its toxins to world agriculture and food safety, the well- supported evolutionary framework developed in the present study should help guide future comparative phylogenetic and genomic studies on this genus. Accomplishments 01 Identification of unexpected Fusarium head blight diversity in new wheat production areas. Fungi within the Fusarium graminearum species complex are responsible for economically destructive diseases of wheat, barley, and other cereals world-wide. In addition, these fungi contaminate grain with trichothecene mycotoxins that pose a significant threat to food safety and animal health. As part of a project to establish a global picture of F. graminearum species complex diversity, ARS, Bacterial Foodborne Pathogens and Mycology Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, determined the prevalence of F. graminearum complex species and toxins associated with diseased wheat in Uruguay. The results indicated that F. asiaticum and the nivalenol toxin type predominated in diseased wheat from areas where rice production is common. These results are similar to those we recently published indicating that F. asiaticum and the nivalenol toxin type may have been introduced into a major rice-producing region of the United States. This is a significant concern for food safety and animal health, because nivalenol is considered more toxic than the deoxynivalenol, which is the most common toxin type in much of the United States, Europe, and South America. Significant differences in aggressiveness and fungicide sensitivity were also observed between different species and toxin types indicating the need to consider this pathogen diversity in development of disease control programs. As such, the results are critical to promoting food safety and cereal production through improved detection of novel F. graminearum species complex pathogens and through plant quarantine and variety improvement efforts that account for the entire spectrum of F. graminearum species complex pathogens and toxin types. 02 Determination of the toxigenic and pathogenic diversity within Fusarium. Fusarium species comprise one of the most economically important groups of fungi. These fungi are responsible for diseases of a wide variety of agriculturally important plants and are an emerging group of human pathogens. In addition, the toxins produced by some species of Fusarium pose a constant threat to plant and animal health and food safety, causing multi-billion U.S. dollar losses to world agriculture annually. ARS, Bacterial Foodborne Pathogens and Mycology Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, used DNA sequence data to clarify the limits of diversity within Fusarium and to assess the distribution and evolution of toxigenic and pathogenic diversity within this group of fungi. In addition, we published an up-to-date review of the diversity, geographic distribution, host preferences, and trichothecene mycotoxin potential of Fusarium head blight pathogens that cause significant diseases of cereals and contaminate grain with deoxynivalenol (DON) and other toxins. These data will be of interest to plant pathologists, mycotoxicologists, plant breeders, and quarantine officials interested in the identification and differentiation of Fusarium, enable prediction of the toxigenic or pathogenic potential of poorly studied species within this group, and provide a robust framework for future comparative analyses of this agronomically and medically important group of fungi.
Impacts
(N/A)
Publications
- Aoki, T., Ward, T.J., Kistler, H.C., O'Donnell, K. 2012. Systematics, phylogeny and trichothecene mycotoxin potential of Fusarium head blight cereal pathogens. Mycotoxins. 62(2):91-102.
- Ratani, S.S., Siletzky, R.M., Dutta, V., Yildirim, S., Osborne, J.A., Lin, W., Hitchins, A.D., Ward, T.J., Kathariou, S. 2012. Heavy metal and disinfectant resistance of Listeria monocytogenes from foods and food processing plants. Applied and Environmental Microbiology. 78(19):6938- 6945.
- Short, D.P., O'Donnell, K., Thrane, U., Fog Nielsen, K., Zhang, N., Juba, J.H., Geiser, D.M. 2013. Phylogenetic relationships among members of the Fusarium solani species complex in human infections and the descriptions of F. keratoplasticum sp. nov. and F. petroliphilum stat. nov. Fungal Genetics and Biology. 53(2013):59-70.
- O'Donnell, K., Rooney, A.P., Proctor, R., Brown, D.W., McCormick, S.P., Ward, T.J., Frandsen, R.N., Lysoe, E., Rehner, S.A., Aoki, T., et al. 2013. Phylogenetic analyses of RPB1 and RPB2 support a middle Cretaceous origin for a clade comprising all agriculturally and medically important fusaria. Fungal Genetics and Biology. 52:20-31.
- Lee, S., Rakic-Martinez, M., Graves, L.M., Ward, T.J., Siletzky, R.M., Kathariou, S. 2013. Genetic determinants for cadmium and arsenic resistance among Listeria monocytogenes serotype 4b isolates from sporadic human listeriosis patients. Applied and Environmental Microbiology. 79(7) :2471-2476.
- Ward, T.J. 2013. Identification and subtyping of Listeria monocytogenes. In: de Fillipis, I., McKee, M.L., editors. Molecular Typing in Bacterial Infections. New York, NY: Springer Science and Business Media. p. 27-38.
- Short, D.G., O'Donnell, K., Zhang, N., Juba, J.H., Geiser, D.M. 2011. Widespread occurrence of diverse human pathogenic types of the fungus Fusarium detected in plumbing drains. Journal of Clinical Microbiology. 49(12):4264-4272.
- Kasson, M.T., O'Donnell, K., Rooney, A.P., Sink, S.L., Ploetz, R.C., Ploetz, J.N., Konkol, J.L., Carrillo, D., Freeman, S., Mendel, Z., et al. 2013. An inordinate fondness for Fusarium: Phylogenetic diversity of fusaria cultivated by ambrosia beetles in the genus Euwallacea on avocado and other plant hosts. Fungal Genetics and Biology. 56(2013):147-157.
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416): Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet, 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance, and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). This research is directed at developing robust Fusarium head blight cereal pathogen control strategies and enhanced methods for identification and characterization of species responsible for mycotoxin contamination of cereals and other food. In order to facilitate accurate identification of toxigenic and pathogenic fusaria via the Internet, we expanded the DNA sequence-based informational databases Fusarium-ID (http://isolate.fusariumdb.org) and Fusarium MLST (http://www.cbs.knaw. nl/fusarium) to include data on the phylogenetic spectrum of fusaria. In addition, genes responsible for the production of several toxins were identified in the unpublished whole genome sequences of two Fusarium species that cause diseases of plants, and the phylogenetic distribution of toxin genes and gene clusters was mapped on the first robust molecular phylogeny of Fusarium. This research provides a framework for determining toxin potential across the genus. In order to develop an understanding of agriculturally-significant variation within Fusarium head blight (FHB) pathogen populations in the United States and around the world, we produced an initial assessment of their diversity and evolutionary relationships within and between FHB populations from five continents. In order to generate a more complete picture of global FHB diversity, we sequenced large regions of the genomes of strains representing FHB populations from around the globe. These data are being used to identify recent and potential future movement of FHB pathogen populations and to detect introductions of invasive pathogen populations. These data will also be used to identify regions of the genome that are responsible for observed differences in growth, toxin production, and aggressiveness in order to improve disease modeling, detection, and control strategies. In addition, we completed an initial survey of FHB pathogens collected from wheat in the Midwestern United States, and initiated studies of diverse FHB populations in France and Brazil in order to evaluate host-preference and assess the potential threat posed by FHB species and populations from outside the United States. Finally, we conducted an analysis of the growth and toxin production characteristics for a series of FHB populations collected from across Canada in order to determine why an introduced FHB population has been so successful in western Canada. This information will be analyzed in order to provide novel insights into disease control strategies aimed at reducing the spread of an invasive, and highly toxigenic, FHB pathogen population in the United States and Canada. To improve our capacity to conduct comparative genomic analyses of Fusarium, we have established a next-generation sequencing facility at NCAUR. An Ion Proton semiconductor sequencing system has been acquired for sequencing fungal genomes and transcriptomes, and for resequencing large fragments of the Fusarium genome across populations. In order to facilitate analysis and storage of the data generated from this sequencer, we are installing a computational cluster, an 80 terabyte network attached storage server, and genome analysis software. Accomplishments 01 Enabling rapid identification of toxigenic and pathogenic Fusarium speci Fusarium species rank among the most economically destructive plant pathogens and mycotoxigenic fungi, posing a constant threat to plant and animal health, and food safety. ARS scientists in the Bacterial Foodborn Pathogens and Mycology Research Unit, National Center for Agricultural Utilization Research, Peoria, IL, in collaboration with agricultural scientists in Denmark, Israel, Japan, The Netherlands, and Norway, determined that DNA sequence data could be used to accurately type agriculturally important pathogens and help predict toxin potential. In addition, the researchers identified genes responsible for the productio of several toxins injurious to humans and plants in the whole genome sequence of two phytopathogenic Fusarium species. Lastly, the DNA sequen data have been incorporated into Fusarium-ID (http://isolate.fusariumdb. org, at the Pennsylvania State University, Philadelphia, PA, and Fusariu MLST (http://www.cbs.knaw.nl/fusarium) at the Centraalbureau voor Schimmelcultures (CBS-KNAW) Biodiversity Center, Utrecht, The Netherland two web-accessible sites dedicated to promoting DNA sequence-based identifications of pathogenic and toxigenic fusaria via the Internet. Th two websites promote agricultural biosecurity worldwide by facilitating global molecular surveillance of pathogenic fusaria and by enabling plan quarantine officials, plant breeders, and plant pathologists to accurate detect and identify these pathogens for the first time.
Impacts
(N/A)
Publications
- Sarver, B.A., Ward, T.J., Gale, L.R., Broz, K.L., Kistler, H.C., Aoki, T., Nicholson, P., Carter, J., O Donnell, K. 2011. Novel fusarium head blight pathogens from Nepal and Louisiana revealed by multilocus genealogical concordance. Fungal Genetics and Biology. 48(12):1077-1152.
- Lee, S., Ward, T.J., Siletzky, R.M., Kathariou, S. 2012. Two novel type II restriction-modification (RM) systems occupying genomically equivalent locations on the chromosomes of Listeria monocytogenes strains. Applied and Environmental Microbiology. 78(8):2623-2630.
- O Donnell, K., Humber, R.A., Geiser, D.M., Kang, S., Park, B., Robert, V.A. , Crous, P.W., Johnston, P.R., Aoki, T., Rooney, A.P., Rehner, S.A. 2011. Phylogenetic diversity of insecticolous fusaria inferred from multilocus DNA sequence data and their molecular identification via FUSARIUM-ID and Fusarium MLST. Mycologia. 104(2):427-445.
- Lee, S., Ward, T.J., Siletzky, R.M., Kathariou, S., Graves, L., Sperry, K., Wolf, L. 2012. Atypical Listeria monocytogenes Serotype 4b strains harboring a lineage II-specific gene cassette. Applied and Environmental Microbiology. 78(3):660-667.
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) The overall goal of this project is to contribute to the effective control of toxigenic Fusarium, especially those responsible for FHB of small grain cereals, in order to enhance food safety and crop production in the U.S. and around the world. The proposed project is designed to produce a robust evolutionary framework for understanding the genetic and phenotypic diversity, geographic distribution and population biology of toxigenic fusaria, and will result in novel technologies for the rapid detection, identification and control of toxigenic fusarial pathogens of critical importance to food safety and food security. This framework will also support and facilitate work by the global Fusarium research community. The specific objectives are: Objective 1: characterize the genetic diversity and mycotoxin potential of Fusarium head blight and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational database to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet. Objective 2: Determine the global population structure of F. graminearum and identify genetic variation associated with population-level difference in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance. Objective 3: Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. Approach (from AD-416) Toxins produced by plant-pathogenic Fusarium pose a significant threat to food safety and place a major burden on the world�s agricultural economy. The primary objectives of the proposed research are to: 1) Characterize the genetic diversity and mycotoxin potential of Fusarium head blight (FHB) and other fusarial pathogens, develop novel pathogen detection technologies, and expand web-accessible informational databases to facilitate the rapid and accurate identification of toxigenic fusaria via the Internet; 2) Determine the global population structure of F. graminearum and identify genetic variation associated with population- level differences in growth, reproduction, and toxin accumulation phenotypes as a means to improve pathogen modeling and surveillance; and 3) Characterize the mechanisms that drive the diversification and adaptive evolution of virulence genes in Fusarium genomes as well as host defense genes involved in immunogenicity and disease response. These complementary objectives are directed at developing robust pathogen control strategies through elucidating the evolution, population structure, phenotypic diversity, host range, geographic distribution, and adaptive potential of toxigenic fusaria. In addition, the planned research will produce enhanced methods for identification and characterization (e.g. toxin type, toxin accumulation potential, and host preference) of Fusarium responsible for mycotoxin contamination of cereals and other food. The information and molecular tools developed as a result of this project will address the needs of small grain cereal producers, food and feed processors, the United States Department of Agriculture (USDA), Federal Grain Inspection Service (FGIS), the USDA Animal and Plant Health Inspection Service (APHIS), and the Food and Drug Administration (FDA). This research is directed at developing robust Fusarium head blight cereal pathogen control strategies and enhanced methods for identification and characterization of species responsible for mycotoxin contamination of cereals and other food. The following two complementary approaches were employed. First, Fusarium pathogens were characterized genetically to develop novel pathogen detection technologies and to expand web-accessible informational databases to facilitate the rapid and accurate identification of toxin-producing pathogens via the Internet. Secondly, global population genetic studies were conducted to improve Fusarium head blight pathogen surveillance. Accomplishments 01 Some Fusarium pathogens prefer wheat, others prefer corn. Understanding the spectrum of pathogens that cause Fusarium head blight of wheat and barley and ear rot of corn, and the toxins they produce, are essential f developing robust disease control strategies and cultivars with broad based resistance to these economically devastating diseases. To assess possible host preferences and toxin potential, Agricultural Research Service (ARS) scientists from the Bacterial Foodborne Pathogens and Mycology Research Unit in Peoria, IL, DNA typed 560 Fusarium isolates fr wheat, barley and maize. Although F. graminearum was the dominant head blight pathogen of wheat and barley, ear rot of corn was caused exclusively by F. boothii, suggesting that the latter species is better adapted to infect corn. Because the exotic pathogen F. boothii was recently detected within the U.S., annual surveys are needed to monitor whether this new pathogen is spreading into major production areas and t guide selection of corn cultivars with the greatest resistance to this pathogen.
Impacts
(N/A)
Publications
- Boutigney, A., Ward, T.J., Van Coller, G.J., Flett, B., Lamprecht, S.C., O Donnell, K., Viljoen, A. 2011. Analysis of the Fusarium graminearum species complex from wheat, barley, and maize in South Africa provides evidence of species-specific differences in host preference. Fungal Genetics and Biology. 48(9):914-920.
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