Document Type

Thesis - University Access Only

Award Date

2006

Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

Abstract

This dissertation addresses important epidemiological questions pertaining to Fusarium head blight (FHB) of spring wheat in South Dakota. Controlled experiments and observational studies were used to investigate some of the underlying environmental and epidemiological factors influencing this disease. The purpose of this research was to better understand inoculum dynamics and disease development in relation to inoculum load within the FHB system. Several specific objectives were addressed: 1. Determine effects of local inoculum load on disease levels and my cotoxin accumulation in spring wheat in SD; 2. Determine how inoculum load and environment interact to affect disease and mycotoxin accumulation; 3. Determine the effects of environment and inoculum load on differentially susceptible wheat varieties; and 4. Develop a better understanding of the temporal dynamics of airborne FHB inoculum in South Dakota. Data presented herein illustrates that environment was the controlling factor affecting inoculum and disease within the experiments, outweighing inoculum load and cultural practices in determining disease pressure. In general, maize residue and inoculum load were not significant factors influencing FHB though there was more noticeable impact on mycotoxin in grain. Additional data suggests that even moderately resistant germplasm was useful in reducing disease and toxin levels in grain, especially under highly FHB favorable environments. Inoculum monitoring data from six location-years indicated that airborne inoculum was related to weather parameters from 1 to 4 days prior to inoculum capture, indicating a lag in response to environmental factors. Furthermore, both ascospores and conidia were shown to be ubiquitous during a large portion of the adult stage of the crop. Data presented also questioned number of common assumptions concerning the FHB system including: the factors triggering ascospore presence in the air; the temporal dynamics of inoculum; and the relative importance of conidia in the FHB system.

Library of Congress Subject Headings

Wheat -- Diseases and pests -- South Dakota

Fusarium diseases of plants -- Epidemiology

Fungal diseases of plants -- Epidemiology

Format

application/pdf

Number of Pages

142

Publisher

South Dakota State University

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