Characterization of Mycotoxin and Furanoterpenoid Production by <i>Fusarium</i> Species Infecting Sweetpotato

Sweetpotato (<i>Ipomoea batatas</i>) production is threatened by Fusarium root rot, which can lead to substantial yield losses and contamination with mycotoxins and phytotoxins. This study investigated the production of mycotoxins by different <i>Fusarium</i> species and isolates in vitro and in vivo, as well as furanoterpenoid compounds produced by sweetpotato in response to <i>Fusarium</i> infection and wounding. Among 37 <i>Fusarium</i> isolates tested, only four <i>F. proliferatum</i> isolates (AS050, AS116, JS603, and NM229) produced significant levels of fumonisins B1 and B2 in sweetpotato roots, with NM229 exhibiting the highest mycotoxin concentrations. Notably, fumonisin production differed between in vivo and in vitro conditions. In sweetpotato roots, fumonisin concentrations for NM229 decreased over time, whereas in liquid culture, concentrations increased. The other isolates produced minimal amounts of fumonisins, with no significant changes over time in either condition. An untargeted metabolomics analysis showed several putative furanoterpenoids, both wounding-induced and <i>Fusarium</i>-specific. Wounding alone triggered production of certain furanoterpenoids, whereas <i>Fusarium</i> infections, particularly <i>F. denticulatum</i> infections, resulted in the highest levels of phytotoxins, including ipomeamarone, 4-hydroxymyoporone, 1-ipomeanol, and 4-ipomeanol. <i>F. acuminatum</i>, <i>F. commune</i>, and <i>F. proliferatum</i> isolates induced some additional putative furanoterpenoids based on observed similar fragmentation patterns. These findings highlight the complex interaction between mechanical damage and <i>Fusarium</i> infection in stimulating phytotoxin production in sweetpotato and emphasize the importance of effective disease management strategies. The detection of high fumonisin levels, exceeding FDA guidelines for human food (2 to 4 ppm), underscores the need for monitoring and controlling <i>Fusarium</i> infections in sweetpotato production.