A bacterial inhibition assay for corynetoxins from parasitized annual ryegrass

Abstract

A rapid and sensitive method is described to detect and measure corynetoxins in extracts of ryegrass seed galls colonized by Corynebacterium rathayi, as well as in crude extracts of pasture samples containing such galls. The assay is done in microtitre plates by incorporating a test organism, C. tntrci, with a series of dilutions of plant extracts. The presence of at least 125 ng ml-1 of toxin inhibits the growth of C. tritici, which can be detected by optical density measurements. There is evidence that growth inhibition is due to the presence of corynetoxins. It is likely the test could also be used to detect the closely related tunicamycin compounds.