PHYTOTOXICITY AND PATHOGENICITY OF FUSARIUM-ROSEUM TO RED-CLOVER

Extracts of culture filtrates from Fusarium roseum are phytotoxic to germinating red clover (Trifolium pratense) seeds. All isolates tested yielded phytotoxic extracts composed of several phytotoxic components. Extracts from the most pathogenic isolate showed only slight host specificity for susceptible red clover seedlings; cucumber (Cucumis sativus) and timothy (Phleum pratense) were most resistant at the lowest concentrations tested. Phytotoxic fractions contain primary amino acids and secondary N-substituted amino acids. Preparative thin-layer chromatography yielded two major phytotoxic fractions: a crude crystalline material containing valine residues and an oil containing valine, isovaleric acid, and aromatic phenyl moieties. These phytotoxins resemble the cyclodepsipeptide antibiotics produced by other pathogenic fungi and by other F. roseum isolates.