Monocerin, a Phytotoxin from Exserohilum turcicum (≡ Drechslera turcica)

Abstract

Infected leaves of the noxious weed johnsongrass were collected in a field with a view to the isolation of toxigenic phytopathogens. Exserohilum turcicum (Pass.) Leonard et Suggs [≡ Drechslera turcica (Pass.) Subramanian et Jain] was isolated from leaf lesions and grown in a liquid culture to yield the known fungal metabolite monocerin (1). This compound was shown to possess (non-specific) phytotoxic activity. Monocerin inhibited seedling growth both of johnsongrass and, to a lesser extent, cucumber. The phytotoxic nature of this compound has not been described previously. Its activity against leaf tissue of two other species, from different plant families, was also demonstrated.