Date of Graduation

12-2013

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Plant Pathology

Advisor

Eugene A. Milus

Committee Member

Burton H. Bluhm

Second Committee Member

Esten R. Mason

Abstract

Wheat grain affected by Fusarium head blight (FHB) contains the mycotoxin deoxynivalenol (DON) that is harmful to humans and animals. Reducing the amount of DON in grain is the goal of management practices for FHB so it is important to understand the factors affecting DON in grain. Some studies on the effects of late-season moisture found increases in DON while others found decreases due to leaching. The objectives of this study were to determine effects of late-season rain and misting on DON concentration in wheat spike tissues and to quantify the amount of DON leached from spikes. Field experiments were conducted on susceptible and moderately resistant wheat cultivars affected by FHB utilizing spike holders to catch water leaching through groups of spikes, rain shelters to protect plots from rain and misting, and a rainfall simulator to apply simulated rain. A critical component of these experiments was to have groups of spikes with similar levels of DON at the beginning of experiments, and methods were developed to make groups as similar as possible and to statistically test for similarity such that dissimilar groups could be eliminated to improve the accuracy of results. Groups of spikes were either not treated or treated with various amounts of rain/simulated rain, and water, grain and chaff were analyzed for DON concentrations. DON was detected in all water samples, indicating that leaching of DON is common. Similar percentages of DON leached from most spike samples that received a particular rain treatment, indicating that the amount leached is proportional to the amount in the sample. Chaff and scabby grain had the highest concentrations of DON and the greatest reductions with rain treatments. Compared to grain from plots protected with rain shelters, grain from comparable plots that were exposed to rain and misting had lower concentrations of DON, indicating that late-season rain reduces DON in grain. A common practice of drying wet samples in a grain dryer was found to degrade a portion of the DON. These results contribute to understanding the role of late-season moisture on DON concentrations in spike tissues and could be beneficial in identifying resistant cultivars to breeders.

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