PRODUCTION OF TOXIN IN ANNUAL RYEGRASS, LOLIUM-RIGIDUM, INFECTED WITH A NEMATODE, ANGUINA SP, AND CORYNEBACTERIUM-RATHAYI

Experiments confirmed that galls induced by nematodes (Anguina sp.), which develop in the place of seeds on ryegrass plants, become toxic to animals when colonized by Corynebacterium rathayi. The distribution of the toxin within the galls was determined by measuring the levels in extracts from the plant and from the parasite components. Bioassays showed that the toxicity of the plant component was considerably greater than that of the bacterial component. An amount of toxin constituting a dose lethal to nursling rats was extracted from between 0.15 and 0.25 mg of plant component compared with between 5.52 and 5.75 mg of bacterial component. These results suggest that the toxin is produced in the plant tissues in response to the presence of the bacterium. Furthermore, the extracts inhibited the growth of C. rathayi in vitro, which suggests that the toxin behaves in a general sense like a phytoalexin. © 1979 CSIRO.