Doctor of Philosophy (PhD)


Plant Pathology and Crop Physiology

Document Type



Rhizopus soft rot (RSR), caused by Rhizopus stolonifer, is a costly postharvest disease of sweetpotato that causes losses after harvested and cured sweetpotatoes are washed and packed. RSR has been effectively managed using synthetic fungicides, but there is a long-standing need for effective non-chemical options. The influence of several host, environmental and/or cultural variables on susceptibility results in year and/or location variations that limit the use of host resistance or predictive systems for management. Further, no alternative methods are consistently effective despite some being toxic to the pathogen. While the role of wound healing after harvest in preventing RSR is well established, the effects of variables that influence storage root susceptibility to RSR or postharvest disease treatments on wound healing processes are unknown. The effects on wound healing processes caused by some of these susceptibility variables and postharvest disease treatments and their relation to RSR incidence suggested that wound healing is among the mechanisms for resistance to RSR. Sodium hypochlorite treatment had less efficacy in RSR control than expected and increased desiccation and slowed lignification on sweetpotato storage roots. Genes involved in phenylpropanoid metabolism, lignin biosynthesis, starch synthesis, starch degradation, and cell wall modification, affecting steps in wound healing were expressed earlier and/or at greater levels in curing conditions than storage conditions. Additionally, the increased expression of an extensin gene by treatments that resulted in reduced RSR incidence warrants the need to further investigate its role in RSR resistance. Collectively, the results demonstrate that, despite the complex interplay of host, environmental and/or cultural variables affecting storage root susceptibility to RSR, wound healing may be a common denominator that could be exploited to identify resistance-associated markers and/or resistance inducers. This research lays the foundation for further exploration into wound healing and the specific pathways affected by host, pathogen, and environmental factors, as well as the different postharvest disease treatments. The overall goal is the development of an effective integrated management program for RSR.



Committee Chair

Clark, Christopher A.

Available for download on Saturday, October 31, 2026