|O Donnell, Kerry|
Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/2/2007
Publication Date: 12/2/2007
Citation: Gale, L.R., Harrison, S.A., Milus, G.A., Ochocki, G.E., O Donnell, K., Ward, T.J., Kistler, H.C. 2007. Spore Development and Trichothecene Mutants of Fusarium graminearum [abstract]. Proceedings of the National Fusarium Head Blight Forum. p. 26.
Technical Abstract: Efforts are ongoing to understand the population structure of Fusarium graminearum sensu stricto (Fg) in the U.S., its dynamics and its significance for small grain production. At previous FHB forums, we described the existence of genetically divergent populations of Fg in some regions of Minnesota and North Dakota (emergent populations) that were in the process of displacing the pre-existing population of Fg and that were also found to be more toxigenic, i.e. produced more deoxynivalenol (DON) on the susceptible variety Norm in greenhouse experiments. Recent population genetic analyses of 1,132 Fg strains from our 2006 collection indicated that the emergent populations are moving further south, as they were found to be present for the first time in South Dakota, at 3.5% of the total Fg population. Greenhouse experiments were conducted that assessed the toxigenic potential of these emergent populations on the commercially important cultivars Alsen, Knudson, Briggs, Freyr, Oklee and Granite that also represent various degrees of FHB susceptibility. Results from these experiments mirrored those from the initial experiments on Norm, i.e. substantially higher DON levels were obtained for all cultivars when inoculated with members of the emergent populations compared to when inoculated with member of the pre-existing Fg population. A second region that we also closely monitor is the southern United States. Previously, we reported that almost all Fg strains from Louisiana were nivalenol producers. Our 2007 collection from Louisiana originated from 17 farmers’ field in three parishes. This collection was established to supplement Fg population information from nurseries. Very similar to population data from nurseries, nivalenol producers of Fg were predominant (79% of isolates). DON producers were mainly of a 3ADON trichothecene type (17% of total). Nivalenol producers also have been identified from Arkansas. From a limited sampling, 12% of isolates from Arkansas were nivalenol producers; among the DON producers the 15ADON trichothecene type was predominant (68% of total). Initial analyses of isolate genotypes established by using a PCR-RFLP marker system determined that overall the Fg population from Louisiana is genetically distinct from the Fg population that is commonly found in the Midwest.