Occurrence of zearalenols (diastereomeric mixture) in corn stalk rot and their production by associated fusarium species.

Zearalenol was extracted from Fusarium-infected stems of corn from southern Italy. The toxin, which appeared as a single compound in various thin-layer chromatography systems, was resolved by high-pressure liquid chromatography into two components. A gas chromatography-mass spectrometry examination of a purified fraction confirmed the natural occurrence of zearalenol as a diastereomeric mixture and led to the identification of alpha (56 ng/g) and beta (27 ng/g) isomers. Among nine Fusarium species found associated with stalk rot in corn, only Fusarium culmorum (F. roseum ;Culmorum') and F. equiseti (F. roseum ;Gibbosum') produced zearalenol and always produced it in a diastereomeric mixture of alpha and beta isomers.