BIOHERBICIDAL POTENTIAL OF FUSARIUM-MONILIFORME AND ITS PHYTOTOXIN, FUMONISIN

An isolate of Fusarium moniliforme (Sheldon) (JW #1) was discovered on greenhouse-grown jimsonweed in Mississippi, U.S.A., in 1990. Applications of aqueous suspensions of spores/mycelia (> 1 X 10(7) propagules ml-1) grown on potato-dextrose agar to the potted soil in which 2- to 4-wk-old jimsonweed plants were grown caused local lesions or mosaic-like patterns on the leaves and inhibited growth. Application of lesser doses to the leaves only produced no visual effects. When the fungal suspensions were applied at higher dosages, (> 1 X 10(7) propagules ml-1) either by soil drench or subirrigation, symptoms such as local lesions or a mosaic-like pattern on the leaves appeared and plant growth was inhibited. When the fungus was grown on an autoclaved rice medium and the ground mixture applied to jimsonweed plants, the plants wilted within 24 h and died after 48 h. Crude and cell-free filtrates of the fungal-rice culture also killed 1- to 2- and 3- to 4-week-old plants after 24 to 72 h. A major toxin identified was fumonisin B1, isolated from fermented rice at 400-mu-g g-1. Fumonisin B1 applied in water at 2.5-mu-g 100-mu-l-1 to excised jimsonweed leaves caused the same symptomology (i.e., soft rot diffusing along leaf veins) within 24 h as the cell-free extract or the crude culture filtrates. Similar damage occurred to intact plants treated with crude or cell-free filtrates or purified aqueous fumonisin B1 solutions.