Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School



Of twenty Bacillus species tested, only five were capable of I vitro inhibition of several wheat pathogens. The mode of inhibition of these five Bacillus species was due to the production of an extra cellular peptide antibiotic which caused disruption of the plasma membrane. Various other physical and chemical characteristics of the antibiotics were also investigated. When applied as seed treatments on spring wheat, the five Bacillus species did not produce significant yield differences. Low soil temperatures at spring wheat planting may have been responsible for the failure of response. The five Bacillus species, B. subtilis var. niger (originally received as B. globigii), B. subtilis, B. polymyxa, B. thuringiensis subsp. Sotto and B. sibtilis (originally received as B. uniflaellatus) required a temperature of 14 C or higher to grow and a temperature of 16 C or higher to produce their antibiotic(s). Our results also indicated that six phytopathogentic organisms, used as test organisms, are capable of growth at temperatures of 10 and 12 C. Soil temperatures at spring wheat planting time are generally 7-10 C and may be too low to allow for Bacillus success as a biocontrol agent.

Library of Congress Subject Headings

Wheat -- Diseases and pests

Pests -- Biological control

Bacillus (Bacteria)

Soil microbiology



Number of Pages



South Dakota State University