APS Abstract of Presentation

Association between post-anthesis infection and deoxynivalenol accumulation in grain from spikes without visual symptoms of Fusarium head blight
K. J. ODENBACH (1), M. J. Guttieri (1), C. H. Sneller (1), L. V. Madden (1), P. A. Paul (1)
(1) Ohio State University - OARDC, Wooster, OH, USA
Phytopathology 99:S96

Deoxynivalenol (DON) is a mycotoxin that accumulates in wheat spikes infected by Fusarium graminearum, the causal agent of Fusarium head blight (FHB). In general, DON levels are positively correlated with symptoms of FHB, but DON can also exceed the critical threshold of 2 ppm when no symptoms of FHB are visible. Wheat is most susceptible to infection at anthesis; however, late-season infections do occur and can result in DON contamination. This study examined the association between post-anthesis infection and DON in grain from asymptomatic wheat spikes. Three soft red winter wheat cultivars (Cooper, susceptible; Hopewell, moderately susceptible; and Truman, moderately resistant) were inoculated 1, 2 and 3 wk after anthesis with different spore concentrations. Milled grain from asymptomatic spikes was tested for DON. F. graminearum biomass was quantified by amplifying Tri5 DNA from grain samples using quantitative RT-PCR. DON values ranged from not detectable (<0.05 ppm) to 3.1 ppm. The amount of Tri5 DNA ranged from 0.02 to 2.53 ng/g of grain. There was a significant positive correlation between fungal biomass and DON across cultivar and infection timing (r = 0.69). The infection time with the strongest correlation was 1 wk post-anthesis, with r = 0.86. The strongest correlation for cultivar was for Hopewell (r = 0.62), the cultivar that accumulated the most DON and contained the greatest amount of fungal biomass.

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