Abstract
Potato (Solanum tuberosum) is a crucial global food crop, yet its production is threatened by fungal pathogens such as Pythium ultimum and Colletotrichum coccodes, which cause significant yield losses and impact tuber quality. In this study, we investigated the antifungal properties of various Streptomyces and Bacillus isolates against these pathogens. The Streptomyces isolates, known for their prolific secondary metabolite production, were selected for their varying efficacy against these fungi. Despite the anticipated potential, Streptomyces isolates exhibited limited antifungal activity against Pythium ultimum and only moderate activity against Colletotrichum coccodes. In contrast, Bacillus isolates, particularly B1, demonstrated strong inhibition of C. coccodes, although this activity diminished after the removal of the live bacteria and after fractionation. The study has several potential factors influencing these outcomes, including the degradation of bioactive compounds during the fermentation, concentration, storage, and fractionation processes. The 10-day fermentation period was chosen based on the typical peak of secondary metabolite production in Streptomyces; however, the transition from solid to liquid media may have affected metabolite stability. Furthermore, the study suggests that repeated subculturing over six years may have led to genetic drift or loss of metabolite production in Streptomyces isolates. Additionally, the presence of Bacillus contaminants in an old DMSO stock added complexity to the results, particularly in early bioassay replicates. This study highlights the challenges of maintaining bioactive compound efficacy through various stages of microbial processing and suggests that alternative extraction and fractionation methods, as well as a focus on preserving synergistic compound interactions, may enhance the development of effective biocontrol agents for agricultural use.
Degree
MS
College and Department
Life Sciences; Plant and Wildlife Sciences
Rights
https://lib.byu.edu/about/copyright/
BYU ScholarsArchive Citation
Henrie, Jacob R., "Investigating Secondary Metabolites of Streptomyces and Bacillus Bacteria that Inhibit Colony Growth of Pathogenic Potato Fungi (Colletotrichum coccodes, Pythium ultimum)" (2024). Theses and Dissertations. 10584.
https://scholarsarchive.byu.edu/etd/10584
Date Submitted
2024-11-12
Document Type
Thesis
Handle
http://hdl.lib.byu.edu/1877/etd13421
Keywords
Streptomyces, Bacillus, secondary metabolites, Pythium leak, Black Dot
Language
english