Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 9, 2010
Publication Date: December 9, 2010
Citation: Gale, L.R., Ward, T.J., Kistler, H.C. 2010. A subset of the newly discovered Northland population of Fusarium graminearum from the U.S. does not produce the B-type trichothecenes DON, 15ADON, 3ADON or NIV. Meeting Abstract. Technical Abstract: Between 2003 and 2006, large-scale population surveys of Fusarium graminearum from North Dakota (ND), South Dakota (SD) and Minnesota (MN) were conducted to determine the spatial and temporal dynamics of the emergent population of F. graminearum that has been determined to be more toxigenic than the pre-existing and widespread Midwestern (MW) 15ADON population. To efficiently determine population membership, we developed three VNTR markers with alleles that are specific to the known populations. After genotyping and determination of trichothecene type of more than 6,000 isolates, and after identifying and excluding species other than F. graminearum (e.g. F. culmorum, F. poae) and clones from repeat isolations from the same wheat head, we identified roughly 400 F. graminearum isolates that did not display population specific VNTR patterns. Further genotyping these with PCR-RFLPs, together with members from known populations for comparison, and subsequent analysis with STRUCTURE, a Bayesian model-based clustering software that assigns multilocus genotypes probabilistically to K populations, revealed the presence of three populations, the MW15ADON population, the emergent population (including 3ADON and 15ADON types) and a newly identified population that we named the Northland population. We currently have identified 176 isolates in our collection that belong to this population, whereby the majority originated from MN (77%), followed by ND (19%), and SD and WI (2% each). Isolates were not only recovered from wheat, but also from grasses in non-agricultural regions such as the Arrowhead region of MN (extreme Northeast MN). About 2/3 of these isolates were typed as 15ADON and 1/3 as 3ADON. Twelve isolates of each trichothecene type were then examined for aggressiveness and mycotoxin potential on the susceptible wheat cultivar Norm in the greenhouse. While all spikelets inoculated with the 15ADON types of the Northland population contained as excepted DON>15ADON>3ADON, spikelets inoculated with eleven of the twelve 3ADON isolates of the Northland population did not contain detectable levels of any of the common trichothecenes. These 3ADON type isolates all had different PCR-RFLP genotypes, and were therefore not clonally related; they were also geographically widespread. These observations lead us to hypothesize that this phenotype is heritable and that there may not be a selective disadvantage against this phenotype. After point-inoculation into a central spikelet, these isolates also spread in the spike and symptoms caused by these isolates could visually not be distinguished from isolates that produce the common trichothecene toxins. Inoculations with only one of the 3ADON Northland isolates yielded plant material with the expected trichothecenes.