Interference of selected fungicides, plant growth retardants as well as piperonyl butoxide and 1-aminobenzotriazole in trichothecene production of Fusarium graminearum (strain 4528) in vitro

Fusarium, head blight may cause significant quantitative and qualitative yi eld losses in cereals. In addition, the consumption of grains contaminated by Fusarium mycotoxins (e. g., trichothecenes) constitutes a health risk fo r animals and humans. In this study the effect of selected fungicides, plan t growth retardants as well as of piperonyl butoxide and aminobenzotriazole has been examined in Fusarium graminearum strain 4528 regarding the inhibi tion of trichothecene production relative to mycelium growth. An in vitro t est system for production of trichothecene toxins in liquid nutrient medium has been established. The strain of F. graminearum 4528 proved to be a rel iable producer of 3-acetyldeoxynivalenol (3-ADON) and deoxynivalenol (DON). Various fungicides (e. g., prochloraz, carbendazim) and plant growth retard ants (e. g., ancymidol, flurprimidol and BAS 111) retarded with increasing concentrations 3-ADON to a similar extent as mycelium growth. On the other hand, in the presence of a small range of sublethal concentrations of some compounds (e. g., fluquinconazole, thiabendazole, tebuconazole), 3-ADON pro duction was increased compared to mycelium growth. However, at higher dosag es, these compounds dimished 3-ADON production and mycelium growth either t o similar levels (e. g., tebuconazole) or mycotoxin production was more eff ectively inhibited than mycelium growth (e. g., thiabendazole). The guanidi ne-derivatives guazatine and iminoctadine induced a marked increase of 3-AD ON production in relation to the mycelium growth in the concentration range tested. Pyrimethanil over the concentration range studied retarded 3-ADON productio n more effectively than mycelium growth. Piperonyl butoxide (PBO), used as synergist of insecticides and herbicides by interfering in cytochrome P450 monooxygenases, inhibited selectively trichothecene production. While mycel ium growth was only slightly retarded over a concentration range (0,25-3 mm ol/l), 3-ADON production was severely inhibited even at the lowest PBO conc entration applied. 1-Aminobenzotriazole (ABT), an inhibitor of P450 mono-ox ygenases, impaired 3-ADON production more effectively than mycelium growth.