Free Water Can Leach Mycotoxins from Fusarium-infected Wheat Heads

The objective of this study was to examine the impact of free environmental moisture, such as from rainfall, on disease development and mycotoxin production and accumulation in planta. In greenhouse experiments in 2009, two single Fusarium graminearum isolates were used to inoculate spikes of three wheat cultivars: Alsen, 2375 and Wheaton at anthesis. On each wetting event/sampling day (7, 14, 21 or 28 days after inoculation), FHB severity was assessed and five pots of each of the two cultivar/isolate treatments were subjected to a wetting event. At the end of the wetting event, the spikes were sampled both from the plants that received the wetting treatment and those that did not and analysed for mycotoxins. Run-off water samples were also taken 3 h after the start of irrigation and immediately after the wetting treatment concluded and analysed for mycotoxins. The results showed despite statistically similar FHB severity, the levels of DON and other mycotoxins detected were significantly lower in the plants receiving a single wetting event compared to the control. The levels of DON in wetted plants were lower up to 36% in Alsen, 52% in 2375 and 41% in Wheaton compared to that of corresponding controls. DON and 15-ADON were also detected in run-off water from the inoculated heads of all cultivars examined. Based on the results of this study, it can be concluded that DON and its derivatives produced in planta can be leached out from the host tissues by free water on contact with plant surfaces.