EXPLORING FUSARIUM HEAD BLGHT DISEASE DEVELOPMENT AND BIOLOGICAL CONTROL
Open Access
- Author:
- Behari, Anita Leishma
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 03, 2018
- Committee Members:
- Gretchen Anna Kuldau, Dissertation Advisor/Co-Advisor
Gretchen Anna Kuldau, Committee Chair/Co-Chair
Maria Del Mar Jimenez Gasco, Committee Member
Timothy W Mcnellis, Committee Member
Maryann Victoria Bruns, Outside Member
Yinong Yang, Committee Member - Keywords:
- Deoxynivalenol
Mycotoxin
Fusarium
Biological Control
Fusarium Head Blight - Abstract:
- Fusarium head blight (FHB) is a fungal disease of wheat and other cereals caused by species of Fusarium, namely Fusarium graminearum. This disease is sporadic and highly weather dependent, and affects wheat production globally resulting in reduced grain quality and contamination with mycotoxins. The mycotoxin most commonly associated with FHB is deoxynivalenol (DON). DON is a virulence factor in disease, as well as toxic to plants, humans, and animals. Ultimately, reducing DON contamination in grain depends on preventing infection and subsequent disease. Current mitigation strategies for FHB include the use of moderately resistant cultivars and fungicides; however, when conditions are conducive to disease development even a combination of mitigation strategies offers limited control. Improving mitigation of FHB depends on an improved understanding of disease development, especially the effects of weather variables on facilitating infection, disease, and DON accumulation in cultivars with varying levels of resistance. Additionally, given that global wheat production is threatened by rust and wheat blast, identifying other mitigation strategies for FHB will support flexibility with disease control. The purpose of this dissertation was to examine the effects of temperature on disease development and DON accumulation in cultivars varying in resistance to FHB, and to explore biological control (biocontrol) as an additional tool for FHB mitigation. The first objective was to examine the effects of cultivar (moderately resistant: ‘Alsen’ and susceptible: ‘Wheaton’) and temperature (15°C and 22°C) on fungal spread, ergosterol accumulation, and DON accumulation in Fusarium head blight diseased wheat. Using the point inoculation technique, the florets of the central spikelet of wheat heads were inoculated with a macroconidia suspension. Wheat heads were harvested every two days over a period of thirty days, with one floret per spikelet used to collect data on incidence of F. graminearum, while the other floret was used for extraction of DON and ergosterol. The moderately resistant cultivar ‘Alsen’ was found to have the least fungal spread, DON, and ergosterol, while 15°C also reduced fungal spread, DON, and ergosterol. The combination of ‘Alsen’ 15°C had the lowest F. graminearum incidence, and the least DON and ergosterol. The second objective was to isolate, identify, and characterize microbes from environmental sources in Pennsylvania, with the abilities to inhibit F. graminearum and remove DON from liquid culture. Additionally, the third objective was to screen Bacillus isolates isolated from quinoa in Bolivia and Ecuador for the same abilities. Microbes (mostly bacteria) were isolated from soil and plant material using various media and selected based on morphology for co-culturing with F. graminearum, while samples of soil and plant material were incubated in mineral salt media with DON and tested individually using GC-ECD to monitor DON removal from liquid culture. A total of 151 microbes were screened for inhibition, 59 of which were isolated from mineral salt media containing DON. Of the 151 microbes, 12 were found to inhibit F. graminearum, of which 4 were also able to reduce DON levels in culture. Five other microbes from the mineral salt media incubations were found to significantly decrease DON in culture, but did not inhibit F. graminearum. The fourth objective was to field test spray treatments of two microbes, one able to inhibit F. graminearum and the other able to remove DON, separately and combined, for their effects on FHB disease incidence, head severity, Fusarium damaged kernels (FDK), and DON accumulation in a FHB moderately resistant and a FHB susceptible cultivar of wheat. Using non-parametric two-way ANOVA analyses between medians, we found that treatment, cultivar, and treatment*cultivar were significant for all measured variables. Additionally, for some of the measured variables, microbe treatments were found to exacerbate disease and DON accumulation. Future research can further elucidate the effects of weather variables on affecting disease and DON accumulation in cultivars with varying degrees and types of resistance. Biocontrol research can focus on supporting the establishment and antagonistic activities of biocontrol agents in field environments. This dissertation contributes to furthering the understanding of factors influencing disease and DON levels, as well as the use of F. graminearum inhibition and DON removal for FHB biocontrol.