Regulation of sexual reproduction in Gibberella zeae (Fusarium roseum 'Graminearum') by F-2 (Zearalenone)

Abstract

Zearalenone or F-2 [2,4-dihydroxy-6-(10-hydroxy-6-oxo-trans-1-undecenyl)-benzoic acid lactone] is an estrogenic mycotoxin synthesized by Fusarium roseum (Link emend.) Sny. & Hans. 'Graminearum.' In addition to its estrogenic activity in animals, it acts as a sex-regulating hormone in F. roseum, and this is the subject of this paper. When amounts of F-2 ranging from 0.1 ng to 10.0 ng were applied to a 1.0-cm diameter disk of Coons' synthetic medium in agar, perithecial formation was enhanced by as much as 100%. Amounts in excess of 10.0 μg inhibited perithecial formation. F-2 has a periodicity of action relative to both enhancement and inhibition of perithecial formation. The ability of F-2 to enhance was greatest up to 4 days of culture age when amounts optimum (0.1 ng and 1.0 ng) for enhancement were used. Optimum inhibition of perithecial formation with inhibitory amounts (10.0 μg and 100.0 μg) occurred when the culture was from 3 to 4 days old. Dichlorvos (2,2-dichlorovinyl dimethyl phosphate), also called VAPONA, inhibited F-2 biosynthesis as well as production of perithecia. Moreover, when F-2 was applied simultaneously with dichlorvos, the inhibition caused by dichlorvos was reduced. A limited study on structure activity relationships was done with the conclusion that the hydroxyl or ketone in the 6′ position of the undecenyl ring is necessary for activity. Further, unsaturation at the 1′,2′ position on the undecenyl ring of F-2 is associated with inhibitory activity at the higher concentrations.