CHARACTERIZATION AND PURIFICATION OF A PHYTOTOXIN PRODUCED BY FUSARIUM-SOLANI, THE CAUSAL AGENT OF SOYBEAN SUDDEN-DEATH SYNDROME

A phytotoxic polypeptide identified in culture filtrates of Fusarium s olani, the causal agent of soybean sudden death syndrome, was heat uns table, negatively charged, absorbed by 10% charcoal, and destroyed by proteinase K. The toxicity of the culture filtrates and fractions obta ined during purification was bioassayed by measuring browning of soybe an calli. Purification of the phytotoxin was achieved by Sephadex G-50 gel filtration chromatography followed by ion exchange chromatography on a DE-52 column. The purified protein migrated as a single band on sodium dodecyl sulfate-polyacrylamide gels with an estimated molecular weight of 17,000. The sequence of the N-terminal 15 amino acids was d etermined and indicated that a peptide was present. Samples containing this single protein caused browning of soybean calli, necrosis on det ached soybean cotyledons and leaves, and yellowing, curling, and dryin g of attached soybean cotyledons and leaves.