Fusarium pseudograminearum Isolates Show Enhanced Growth and Na+ Uptake but Suppressed Mycotoxin Production After Exposure to NaCl at Different Temperatures

Several <i>Fusarium</i> species have demonstrated the ability to thrive in saline soils and to tolerate or prefer high salt concentrations. In this context, the potential halophilic or halotolerant lifestyle of <i>Fusarium pseudograminearum</i> was investigated. Four isolates (3B, PVS-Fu 7, ColPat-1, and CBS 109956) were grown at different temperatures (10, 15, 20, 25, 30, and 35 °C) and NaCl concentrations (0, 7, 14, 21, and 28 g L^-1), and daily growth, mycotoxin production, and K⁺ and Na⁺ accumulation within hyphae were assessed. All <i>F. pseudograminearum</i> isolates exhibited strong adaptability to saline conditions, with significantly enhanced growth in the presence of NaCl. All isolates accumulated Na⁺ within their hyphae while retaining K⁺. The production of deoxynivalenol (DON) and zearalenone (ZEA) was generally suppressed following NaCl exposure, consistent with the known inhibitory effect of reduced water activity on mycotoxin biosynthesis. However, at 22 °C, two isolates, 3B and CBS 109956, showed no significant differences in ZEA production between the control (no salt) and the medium containing the lowest NaCl concentration tested (7 g L^-1). Notably, isolate 3B, obtained from the halophyte <i>Salicornia europaea</i>, retained the highest levels of both Na⁺ and K⁺ within hyphae and showed the greatest overall adaptation to salinity. These results confirm the hypothesis that the ability of <i>F. pseudograminearum</i> to colonize and infect a halophytic host is indicative of a halophilic lifestyle. In the context of increasing soil salinization, these findings help identify conditions that permit pathogen persistence without hazardous mycotoxin accumulation.