IMPROVING SWEETPOTATO STORAGE CONDITIONS TO MINIMIZE POST-HARVEST FUNGAL DISEASE AND MYCOTOXIN PRODUCTION

Demand for U.S. grown sweetpotatoes, in both the domestic and export markets, has risen steadily in recent years and growers have kept pace by producing between 1.2 and 1.8 million metric tons from 2013 to 2018. Sweetpotato production is limited by a variety of factors, including postharvest diseases like Fusarium root rot. Recently, one of the causal organisms, Fusarium proliferatum was observed producing the carcinogenic mycotoxin fumonsin B1 in infected sweetpotatoes. Additionally, when infected by Fusarium spp. sweetpotatoes are known to produce a phytotoxin ipomeanol, which is acutely toxic to livestock. The factors surrounding production of ipomeanol, fumonsin B1, or other mycotoxins in the sweetpotato-Fusarium interaction are unknown. Thus, the overall goal of this research is to gain insight into the production of toxins in sweetpotatoes during the Fusarium infection cycle. The first objective aims to quantify mycotoxin production in several Fusarium species infecting sweetpotato at specific post-infection timepoints. The second objective seeks to characterize the mechanisms of mycotoxin production and conduct comparative analyses on sweetpotato-infecting isolates collected from different hosts. Finally, the third objective will identify the environmental and host factors that trigger mycotoxin and phytotoxin production in roots during the Fusarium-sweetpotato interaction. By completing objective 1, we will gain insight into which sweetpotato-infecting Fusarium species produce mycotoxins and the quantities that they produce. This knowledge directly impacts animal and human health by helping to identify the cause of mycotoxin contaminated sweetpotatoes. Upon completion of objective 2, we will better understand how the genes expressed by fumonisin B1 producing Fusarium species during infection on sweetpotato differ when infecting potential rotational crops. This will allow for the risk of fumonisin B1 contamination to be assessed based on the previous year's crop and the likelihood of infection. At the completion of objective 3, we will better understand the environmental conditions favoring fumonisin B1 and ipomeanol production and will have gained insight into managing toxin production through cultivar selection and environmental manipulation during storage.