Location: Cereal Disease Lab
2019 Annual Report
Objectives
Objective 1: Discover specific factors involved in pathogenicity, sporulation and toxin synthesis for the FHB pathogen and related fungi by applying genomic and functional approaches.
Sub-objective 1.A. Functionally characterize cellular processes and structures that determine plant pathogenesis.
Sub-objective 1.B. Identify genes uniquely or differentially expressed during development that defines pathogen structure and function.
Objective 2: Relate fungal genotypes to mycotoxin production in fungal strains in field production environments to aid in developing enhanced methods of control.
Sub-objective 2.A. Monitor genetic changes in critical pathogen populations by pathogen surveys.
Sub-objective 2.B. Characterize populations of Fusarium from native North American grasses that may be sources of novel pathogen genotypes and/or host resistance.
Objective 3: Optimize metagenomic and functional approaches to define the phytobiome of healthy and diseased plants naturally infested with the FHB fungus.
Sub-objective 3.A. Characterize phytobiome and soil carbon composition.
Sub-objective 3.B. Determine the relative abundance of competitive phenotypes and impacts on plant productivity.
Objective 4: Identify novel sources of plant disease resistance to FHB and mycotoxins produced by FHB fungi to improve breeding for resistance.
Sub-objective 4.A. Characterize the epigenetic changes of FHB resistant durum cultivars produced by altering the DNA methylation pattern.
Sub-objective 4.B. Characterize durum lines missing a portion of chromosome 2A region that may contain the FHB suppressor locus.
Approach
Improved management strategies are needed to maintain adequate plant disease control. Specific approaches include: 1) Genetic information obtained from the fungal pathogen, Fusarium, will be used to identify genes factors responsible for fungal pathogenesis, possibly leading to novel approaches to control FHB disease and reduce toxin levels in grain; 2) FHB levels, strain diversity, and the nature of associated fungal communities, will be monitored by population genetic and metagenomic approaches improving the ability to forecast the economic impact and the design of effective management strategies; 3) Novel sources of FHB resistance and mycotoxin tolerance will be developed for plants.
Progress Report
In the second full year of the project, USDA-ARS scientists located in St. Paul, Minnesota have made substantial progress in the following Objectives:
Sub-objective 1.A. Functionally characterize cellular processes and structures that determine plant pathogenesis: Deletion mutants were created of Fusarium Tri14 gene and introduced into several genetic backgrounds that allow for fluorescent examination of fungal cells. Additionally, samples of toxin-induced fungi were submitted for proteomic study.
Sub-objective 1.B. Identify genes uniquely or differentially expressed during development that defines pathogen structure and function: RNAseq experiments were completed of Fusarium graminearum during toxin synthesis. Data has been analyzed and being prepared for publication.
Objective 2. Relate fungal genotypes to mycotoxin production in fungal strains in field production environments to aid in developing enhanced methods of control: Surveys for the FHB pathogen found in wheat and native grass species are in progress for the 2019 field season.
Objective 3. Optimize metagenomic and functional approaches to define the phytobiome of healthy and diseased plants naturally infested with the FHB fungus: Currently characterizing interactions of Fusarium and soil microbes for potential antagonistic interactions and tolerance of Fusarium to inhibitory chemicals.
Sub-objective 4.A. Characterize the epigenetic changes of FHB resistant durum cultivars produced by altering the DNA methylation pattern: Sequencing of transcriptome collected from various lines and different infection period has been completed and bioinformatics analysis is continuing.
Sub-objective 4.B. Characterize durum lines missing a portion of chromosome 2A region that may contain the FHB suppressor locus: Populations have been created and advanced and are awaiting genotyping for deletion breaks along the chromosome for further advancement and phenotyping.
Accomplishments
1. Halting fungal "toxin factories" may make small grains safer. Harmful byproducts of fungi, called mycotoxins, threaten food safety and cause losses in wheat and barley yield and grain quality. Little is known about structures within fungal cells that make high-level production of mycotoxins possible. ARS researchers located in St. Paul, Minnesota, have discovered that the fungal products vomitoxin and culmorin that contaminate wheat and barley grain, are produced within specialized portions of fungal cells called toxisomes. The formation of toxisomes converts normal fungal cells into virtual "toxin factories". Moreover, treatments that prevent toxisome formation greatly reduce the ability of the fungus to produce mycotoxins. Such treatments may supplement fungicide applications and be important for developing novel strategies for preventing the contamination of grain with vomitoxin and other mycotoxins.
2. Durum wheat resistance to mycotoxin is stable. Durum wheat is greatly impacted by the disease Fusarium head blight (FHB) which contaminates the grain with the harmful mycotoxin Deoxynivalenol (DON). Selected mutants of durum wheat plants generated by altering GC (Guanine-Cytosine pair) methylation patterns (i.e., 5-methyl-azacytidine treatment) were consistently, over multi-location and year testing, more resistant with less DON than parental lines and cultivar checks. To test the genetic stability of resistance, the most promising lines were crossed to parental lines and current durum cultivars and advanced several generations without selection. The BC1F3 families were tested in the field for disease resistance and several families displayed increased resistance similar to the mutant parent and are being deployed by the durum breeding programs for their cultivar enhancement objective. This new native source of FHB resistance in durum wheat will greatly benefit efforts in breeding for resistant cultivars.
Review Publications
Chen, Y., Kistler, H.C., Ma, Z. 2019. Fusarium graminearum trichothecene mycotoxins: Biosynthesis, regulation and management. Annual Review of Phytopathology. https://doi.org/10.1146/annurev-phyto-082718-100318.
Widinugraheni, S., Nino-Sanchez, J., van der Does, H.C., van Dam, P., Garcia-Bastidas, F.A., Subandiyah, S., Meijer, H.J.G., Kistler, H.C., Kema, G.H.J., Rep, M. 2018. A SIX1 homolog of Fusarium oxysporum f.sp. cubense tropical race 4 contributes to virulence towards Cavendish banana. PLoS One. https://doi.org/10.1371/journal.pone.0205896.
Pirseyedi, S.M., Kumar, A., Ghavami, F., Hegstad, J.B., Mergoum, M., Mazaheri, M., Kianian, S.F., Elias, E.M. 2018. Mapping QTL for Fusarium head blight resistance in a Tunisian-derived durum wheat population. Cereal Research Communications. 47(1):78-87.
Kumar, J., Gunapati, S., Kianian, S., Singh, S.P. 2018. Comparative analysis of transcriptome in two wheat genotypes with contrasting levels of drought tolerance. Protoplasma. 255(5):1487-1504. https://doi.org/10.1007/s00709-018-1237-x.
Liu, Z., Jian, Y., Chen, Y., Kistler, H.C., Ma, Z., Yin, Y. 2019. A phosphorylated transcription factor regulates sterol biosynthesis in Fusarium graminearum. Nature Communications. https://doi.org/10.1038/s41467-019-09145-6.
Boenisch, M.J., Blum, A., Broz, K.L., Gardiner, D.M., Kistler, H.C. 2019. Nanoscale enrichment of the cytosolic enzyme trichodiene synthase near reorganized endoplasmic reticulum in Fusarium graminearum. Fungal Genetics and Biology. 124:73-77. https://doi.org/10.1016/j.fgb.2018.12.008.
Flynn, C.M., Broz, K.L., Jonkers, W., Schmidt-Dannert, C., Kistler, H.C. 2019. Expression of the Fusarium graminearum terpenome and involvement of the endoplasmic reticulum-derived toxisome. Fungal Genetics and Biology. 124:78-87. https://doi.org/10.1016/j.fgb.2019.01.006.
