Date of Award
5-1-2026
Degree Name
Doctor of Philosophy
Department
Agricultural Sciences
First Advisor
Fakhoury, Ahmad
Second Advisor
Bond, Jason
Abstract
Soilborne microorganisms can affect soybeans in multiple ways and can potentially cause catastrophic production losses. Under certain conditions, colonization by the charcoal rot fungus, Macrophomina phaseolina, can be especially damaging because the pathogen is favored by hot and dry conditions. My study investigated whether the bacterium, Bacillus licheniformis SPP22, would be a suitable biocontrol agent to protect soybeans from the M. phaseolina. Different aspects of the suppression of M. phaseolina by B. licheniformis SPP22 were investigated in laboratory and greenhouse experiments. Suppression was achieved through direct inhibition of fungal growth and structural development of the pathogen, and by activating plant defense mechanisms. Further investigation was conducted at the molecular level to explore the interaction between the pathogen M. phaseolina and B. licheniformis SPP22. This study revealed some of the mechanisms by which the bacterium may control M. phaseolina. Our results suggest that B. licheniformis SPP22 may be a viable and inexpensive biocontrol agent for soybean charcoal rot. More generally, these findings could lead to broadly applicable solutions for controlling soilborne diseases, which will help increase agricultural sustainability.
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