|Breunig, Mikaela - Michigan State University|
|Byrne, Adam - Michigan State University|
|Jacobs, Janette - Michigan State University|
|Chilvers, Martin - Michigan State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2019
Publication Date: 10/16/2019
Citation: Breunig, M., Byrne, A.M., Jacobs, J.L., Ward, T.J., Chilvers, M.L. 2019. Characterization of species composition, chemotype, and in vivo and in vitro fungicide sensitivity of Fusarium from wheat and corn in Michigan, USA [abstract].
Technical Abstract: Fusarium species are a major concern due to mycotoxin contamination of wheat and corn grains in North America. To characterize the population of Fusarium in Michigan, over 500 isolates were collected and species composition, chemotype (15-ADON, 3-ADON, NIV, NX) and fungicide sensitivity are being determined. Thus far, F. graminearum was the major species associated with wheat, but members of the Fusarium tricinctum complex, F. culmorum, F. cerealis, and F. poae were found as well. Greater species diversity was found in corn, with a smaller proportion identified as F. graminearum and more identified from the Fusarium fujikuroi complex. In vitro sensitivity to triazole chemistries registered in the United States (metconazole, tebuconazole, and prothioconazole) were assessed with mycelial growth assays. Isolates were most sensitive to metconazole, and less sensitive to prothioconazole and tebuconazole. A small portion of isolates within F. graminearum had EC50 values 10-100 fold greater than sensitive isolates. In order to determine if this reduced sensitivity in vitro would lead to practical resistance, a field trial was established in 2019. A subset of F. graminearum isolates were chosen for investigation, four identified as sensitive in vitro (EC50 0.01 -0.1 ppm), and four with reduced sensitivity in vitro (atleast 10-fold greater). Plots were inoculated with spore suspensions of each isolate 48 hours prior to fungicide applications in a factorial manner in a randomized complete block design. No differences in the relative fungicide efficacy were found, signaling no practical resistance currently exists despite differences in vitro and widespread use in wheat throughout Michigan for the last 10 years. If isolates with EC50 values greater than 10ppm are found in the future, these would warrant further field testing. Interestingly, the isolates classified as sensitive in vitro were actually more pathogenic than those classified as resistant with an average 10% greater incidence, but only 5% on average greater severity. DON production was quantified and was slightly higher for sensitive isolates as well (mean 1.3ppm greater) but was not statistically significant. The efficacy of DON reduction by the fungicide was not significantly impacted by the sensitivity of the isolates. We have yet to explore in vivo sensitivity of species besides F. graminearum, and hope to further explore toxin production in these different species and isolates.