Phyllostictine A, a potential natural herbicide produced by Phyllosticta cirsii: In vitro production and toxicity.

Phyllostictine A is a powerful toxin produced by Phyllosticta cirsii, a potential mycoherbicide of Cirsium arvense. To support its potential use as a natural herbicide, toxin production has been studied using different media and cultural conditions. The toxin content in the crude extracts has been determined by using a HPLC method set up for this purpose. Furthermore, its phytotoxicity has been evaluated on tobacco protoplasts by flow cytometric analysis, and on C. arvense protoplasts, by fluorescence microscopy. The best cultural conditions found allowed to produce more than 28 mg ml-1 of toxin in culture filtrate. The pure metabolite proved to have rapid dose-dependant toxic effects on host and no-host plant protoplasts.