Amanda Gill

Document Type

Thesis - University Access Only

Award Date

2006

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

Abstract

Scab or Head Blight is a fungal disease that infects primarily cereal crops, such as spring and winter wheat, barley, durum, and com. Head Blight is caused by a fungus called Fusarium graminearum. Controlling or eliminating the infection is a main concern to producers, and many measures are currently being taken to make this possible. Some areas of disease control include genetic resistance, chemical control, crop rotation, and staggered planting dates. Another area of disease control is biological control, which uses a microorganism to help control disease. This thesis studies a Bacillus strain, 1 BA, which has been shown to inhibit Fusarium graminearum on plate assays, as well as in field trials. The focus of this research was to further define the bacterial characteristics of the bacterial isolate Bacillus lBA. Biochemical tests were run on this Bacillus strain to help understand how it affects Fusarium. Amylase and chitinase plate assays were used to help determine if Bacillus IBA possessed these enzyme activities. Several different growth media were used to grow 1 BA to help determine which medium would provide the best growth conditions for Bacillus I BA. Endospore production as well as endospore survival were looked at using enriched media. The effect of one month of long term storage, at three different temperatures, was examined to help determine if cell numbers were decreasing. Bacillus I BA was grown at various low pH's, to help determine the extremes of growth. Physical and chemical stressors of high temperature and high NaCl concentration were used to select for I BA growth, while inhibiting natural wheat head microflora. The foliar fungicide, Folicur, was added to growth media used to grow Bacillus IBA, to see if any growth inhibition of IBA occurred due to Folicur. Bacillus 1B A was able to grow at high salt concentration ( 10%) and at high temperature (50°C). The high salt concentrations and the high temperatures were able to inhibit native wheat head microflora, while allowing for Bacillus growth. Evidence was found for the survival, persistence, and growth of IBA on wheat heads, with observed differences in the extent of survival and growth depending on how the cells were cultured and/or applied. When storing IBA for a long period of time (1 month), it was found that storage at room temperature (approximately 27°C) had less of an effect on cell number when compared to storage at 4°C and -20°C. Bacillus IBA was able to grow at a pH of 5.2 at a selected few temperatures. Amylase, but not chitinase activity was observed in IBA. Using selected media, sporulation was induced in 1 BA, and pasteurization did not seem to have an effect on the survival of endospores. The addition of calcium chloride to growth media induced clumping and filament formation in Bacillus 1 BA. The additions of various concentrations ofFolicur did not seem to have an effect on Bacillus IBA growth.

Library of Congress Subject Headings

Grain -- Diseases and pests -- Biological control

Fusarium diseases of plants

Fungal diseases of plants

Bacillus (Bacteria)

Format

application/pdf

Number of Pages

95

Publisher

South Dakota State University

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