Abstract: Fifteen mutant isolates were obtained by ultraviolet ray mutation from parent strain Botrytis cinerea BC-4 and 3 mutant isolates, i.e. BC4-1, BC4-2 and BC4-15, showed strong herbicidal activity, among them, BC4-1 was the best for inhibiting the germination and growth of Digitaria sanguinalis L. and Amaranthus retroflexus L. The results also showed that different pH of PD media had different influences on herbicidal activity and pH 4.0 was the best among the pH values tested. The crude toxin could be extracted using chloroform, petroleum ether and ethyl acetate, and the ethyl acetate extracts had a strongest inhibitory activity on the germination and growth of D. sanguinalis L .and A. retroflexus L. One component with an absorbent peak at 271 nm was separated and obtained from the crude toxin by HPLC. The component, at concentration of 100 mg·L-1, could strongly inhibit the growth of D. sanguinalis L. and could completely inhibit seed germination of D. sanguinalis L. and A. retroflexus L.at concentration of 50 mg·L-1.

Key words: Botrytis cinerea, Toxin, Ultraviolet ray mutation, Herbicide activity, Separation and purification