Flow cytometry as a method for assaying the biological activity of phytotoxins

A flow cytometric method has been developed for the qualitative and quantitative evaluation of the biological activities of phytotoxins from plant pathogenic fungi. The method utilized fresh wheat ( Triticum aestivum L.) leaf protoplast preparations treated with purified phytotoxins, triticone A-B and triticone D. Subsequently, protoplasts were exposed to fluorescein diacetate, and analyzed by flow cytometry. Information acquired included fluorescence owing to esterase activity on fluorescein diacetate, and chlorophyll autofluorescence. Results indicate that triticone A-B has a rapid dose-dependent toxic effect on wheat protoplasts but triticone D has no toxic effect. This method can also yield information on the mechanism of action of phytotoxins that are relatively unstable or available only in small quantities.