Location: Mycotoxin Prevention and Applied Microbiology Research
2019 Annual Report
Accomplishments
1. Reliable markers for predicting wheat resistance to fusarium head blight. Fusarium head blight (FHB) is a devastating fungal disease of wheat which can reduce yield and contaminate grain with harmful mycotoxins. Because FHB outbreaks are strongly associated with weather, wheat varieties are evaluated for resistance to FHB under temperature and moisture conditions that favor disease spread. Although atmospheric carbon dioxide levels are rising, wheat varieties are not currently being screened under higher carbon dioxide levels. To determine if wheat resistance ratings are accurate under elevated carbon dioxide levels, ARS researchers in Peoria, Illinois, in collaboration with scientists at the National Research Council Canada, Ottawa, Canada, examined the amount of infection, mycotoxin contamination, and natural plant defense metabolites in susceptible and moderately resistance wheat grown under current or elevated amounts of carbon dioxide. Elevated carbon dioxide led to changes in plant defenses, disease severity, and mycotoxin contamination. Overall elevated carbon dioxide increased mycotoxin contamination. This research demonstrated that resistance ratings developed for wheat grown at current carbon dioxide levels may not apply under future conditions. Although the levels of several plant metabolites associated with disease resistance changed when the wheat cultivars were grown under elevated carbon dioxide, this research identified a set of metabolic markers that can be reliably used by breeders to select for FHB resistance even under increased atmospheric carbon dioxide.
2. Global and regional contributors to mycotoxin contamination of wheat and barley. Fusarium head blight (FHB) is a destructive disease of cereals crops worldwide and a major food safety concern because FHB pathogens can contaminate grain with vomitoxin and other fungal toxins (mycotoxins). FHB is caused by a diverse set of fungal species that make different mycotoxins. Understanding which FHB species and toxin types are present in an area is key to disease and mycotoxin control programs. In this study, ARS scientists in Peoria, Illinois, worked in collaboration with scientists in Uruguay and Brazil to identify and characterize FHB pathogens from their countries. The most common FHB pathogens of wheat and barley in Uruguay and Brazil, as well as the United States, are Fusarium graminearum with the ability to make a form of vomitoxin. However, a new species, Fusarium subtropicale, was found in Brazil that produces a related mycotoxin with greater toxicity for humans and animals. Analyses of genetic diversity revealed that wheat and barley share a common FHB pathogen population that moves back and forth between these two hosts. The FHB pathogens in this study exhibited different levels of aggressiveness toward barley and different levels of resistance to two commonly used fungicides. These results provide new information on FHB pathogen and mycotoxin prevalence, host distributions, aggressiveness, and fungicide sensitivity that can be used to develop globally applicable and regionally targeted disease and mycotoxin control programs that improve crop production and food safety.
3. Plant disease resistance is weakened by fungal enzyme. Fusarium graminearum is a fungal pathogen that causes Fusarium head blight (FHB) of wheat and other cereals and reduces crop yields and quality by producing mycotoxins. Salicylic acid is an important plant signaling molecule that regulates how the plant responds to fungal pathogens. To reduce the incidence of FHB and mycotoxin contamination of grain, we need to understand how Fusarium overcomes plant defenses to cause disease. ARS scientists in Peoria, Illinois, used genome sequence data to identify a F. graminearum protein that degrades salicylic acid and found that it weakens coordinated plant defenses against FHB. The protein is a new target for disease control and mycotoxin reduction programs that improve crop production and food safety.
4. Fungal protein helps disarm plant defenses to fungal disease. Fusarium head blight (FHB) caused by the fungus Fusarium graminearum is one of the most devastating diseases of wheat and other cereals. FHB results in contamination of grain with fungal toxins, known as mycotoxins, that can be a serious threat to food safety and animal health. A better understanding of how the fungus interacts with the plant and plant defenses is needed to reduce the incidence of FHB and mycotoxin contamination of grain. ARS scientists in Peoria, Illinois, discovered a Fusarium arabinanase, a protein that can degrade plant cell walls during infection in wheat. In addition, they demonstrated that arabinanase reduced the plant immune response to fungal invasion. This protein is a new target for improving resistance to FHB and mycotoxin contamination.
5. Genetic control of trichothecene toxins in a biocontrol fungus. Trichothecenes are a group of mycotoxins that when present in crops pose health risks to people, pets, and livestock. The fungus Fusarium graminearum causes head blight of cereal crops and produces the trichothecene vomitoxin, which is toxic to plants (phytotoxic) and contributes to the ability of the fungus to cause head blight. In contrast, the biocontrol fungus Trichoderma arundinaceum inhibits the growth of many plant disease-causing fungi and produces a trichothecene that is highly toxic to other fungi but harmless to plants. In collaboration with scientists at the University of León, Spain, ARS scientists in Peoria, Illinois, identified a group of genes in T. arundinaceum that control production of trichothecenes that are not phytotoxic. This study provided targets to aid development of methods to counteract the phytotoxic effects of trichothecenes and, thereby, the plant-disease-promoting effects of the toxins.
Review Publications
Whitaker, B.K., Bakker, M.G. 2018. Bacterial endophyte antagonism toward a fungal pathogen in vitro does not predict protection in live plant tissue. FEMS Microbiology Ecology. https://doi.org/10.1093/femsec/fiy237.
Garmendia, G., Pattarino, L., Negrin, C., Martinez-Silveira, A., Pereyra, S., Ward, T.J., Vero, S. 2018. Species composition, toxigenic potential and aggressiveness of Fusarium isolates causing Head Blight of barley in Uruguay. Food Microbiology. 76:426-433. https://doi.org/10.1016/j.fm.2018.07.005.
Cuperlovic-Culf, M., Vaughan, M., Vermillion, K., Surendra, A., Teresi, J., McCormick, S. 2018. Effects of atmospheric CO2 level on the metabolic response of resistant and susceptible wheat to Fusarium graminearum infection. Molecular Plant-Microbe Interactions. https://doi.org/10.1094/MPMI-06-18-0161-R.
Pereira, C.B., Ward, T.J., Tessmann, D.J., Del Ponte, E.M., Laraba, I., Vaughan, M.M., McCormick, S.P., Busman, M., Kelly, A., Proctor, R.H., O'Donnell, K. 2018. Fusarium subtropicale sp. nov., a novel nivalenol mycotoxin-producing species isolated from barley (Hordeum vulgare) in Brazil and sister to F. praegraminearum. Mycologia. 110(5):860-871. https://doi.org/10.1080/00275514.2018.1512296.
O'Donnell, K., McCormick, S.P., Busman, M., Proctor, R.H., Ward, T.J., Doehring, G., Geiser, D.M., Alberts, J.F., Rheeder, J.P. 2018. Marasas et al. 1984 "toxigenic Fusarium species: identity and mycotoxicology" revisited. Mycologia. 110(6):1058-1080. https://doi.org/10.1080/00275514.2018.1519773.
Lindo, L., McCormick, S.P., Cardoza, R.E., Kim, H.-S., Brown, D.W., Alexander, N.J., Proctor, R.H., Gutierrez, S. 2018. Role of Trichoderma arundinaceum tri10 in regulation of terpene biosynthetic genes and in control of metabolic flux. Applied and Environmental Microbiology. 122:31-46. https://doi.org/10.1016/j.fgb.2018.11.001.
Lindo, L., McCormick, S.P., Cardoza, R.E., Busman, M., Alexander, N.J., Proctor, R.H., Gutierrez, S. 2018. Requirement of two acyltransferases for 4-O-acylation during biosynthesis of Harzianum A, an antifungal trichothecene produced by Trichoderma arundinaceum. Journal of Agricultural and Food Chemistry. 67(2):723-734. http://dx.doi.org/10.1021/acs.jafc.8b05564.
Bakker, M.G., McCormick, S.P. 2019. Microbial correlates of Fusarium load and deoxynivalenol content in individual wheat kernels. Phytopathology. https://doi.org/10.1094/PHYTO-08-18-0310-R.
Jacobs-Venter, A., Laraba, I., Geiser, D.M., Busman, M., Vaughan, M.M., Proctor, R.H., McCormick, S.P., O'Donnell, K. 2018. Molecular systematics of two sister clades, the Fusarium concolor and F. babinda species complexes, and the discovery of a novel microcycle macroconidium–producing species from South Africa. Mycologia. 110:1189-1204. https://doi.org/10.1080/00275514.2018.1526619.
Hao, G., McCormick, S., Vaughan, M.M., Naumann, T.A, Kim, H.-S., Proctor, R., Kelly, A., Ward, T.J. 2019. Fusarium graminearum arabinanase (Arb93B) enhances wheat head blight susceptibility by suppressing plant immunity. Molecular Plant-Microbe Interactions. https://doi.org/10.1094/MPMI-06-18-0170-R.
Hao, G., Naumann, T.A., Vaughan, M.M., McCormick, S.P., Usgaard, T., Kelly, A., Ward, T.J. 2019. Characterization of a Fusarium graminearum salicylate hydroxylase. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2018.03219.
Hartman, G.L., McCormick, S.P., O'Donnell, K. 2019. Trichothecene production and pathogenicity of Fusaria isolated from symptomatic soybean roots in Ethiopia and Ghana. Plant Disease. https://doi.org/10.1094/PDIS-12-18-2286-RE.
Cardoza, R.E., McCormick, S.P., Lindo, L., Kim, H.-S., Olivera, E.R., Nelson, D.R., Proctor, R.H., Gutierrez, S. 2019. A cytochrome P450 monooxygenase gene required for biosynthesis of the trichothecene toxin harzianum A in Trichoderma. Applied Microbiology and Biotechnology. 103(19):8087-8103. https://doi.org/10.1007/s00253-019-10047-2.
Lippolis, V., Porricelli, A.C.R., Mancini, E., Ciasca, B., Lattanzio, V.M.T., De Girolamo, A., Maragos, C.M., McCormick, S., Li, P., Logrieco, A.F., Pascale, M. 2019. Fluorescence polarization immunoassay for the determination of T-2 and HT-2 toxins and their glucosides in wheat. Toxins. 11(7):380. https://doi.org/10.3390/toxins11070380.
