Production of Fusarium-mycotoxins by dispersal ascospores of Gibberella zeae

To examine the producibility of Fusarium-mycotoxins such as trichothecenes and zearalenone, dispersal Gibberella zeae were collected in barley fields using the agar plates containing Komada medium, known to be a selective one for Fusarium species, and G. zeae ascospores were also isolated from perithecia found on rice stubbles in crop fields. After cultivation of these fungi on polished rice media, the mycotoxins produced were determined by GLC, HPLC and TLC. Of 32 isolates of dispersal ascospores, zearalenone was found in all cases, and 20 isolates (62.5%) produced the following trichothecenes: nivalenol and fusarenon X (15 isolates), deoxynivalenol and 3-acetyldeoxynivalenol (4 isolates), and T-2 toxin and neosolaniol (1 isolate). As for the trichothecene producibility of ascospores (14 isolates) from rice stubbles, only nivalenol and fusarenon X were produced by 13 isolates (92.9%), and none of other trichotheceneproducers was observed. Thus, dispersal toxigenic ascospores in fields could be efficiently trapped by the simple agar plate method. This fact suggests that it may be possible to assess the incidence of dispersal toxigenic ascospores in crop fields.