Studies on ergot (Claviceps purpurea) of wheat

Ergot [Claviceps purpurea (fr.) Tul.] is an important disease of cereals and grasses in Australia, as grain contaminated with ergot is rejected or heavily discounted in value because of its toxicity to animals and man. Yield losses from the disease are small. The ergots most commonly detected in grain samples are from ryegrass and only rarely are the much larger cereal ergots present. Laboratory studies showed that C. purpurea can be cultured on several synthetic media, however, yeast malt dextrose agar was the best. On this medium the fungus grew well, sporulated abundantly and pathogenic isolates maintained their virulence. Pathogenicity tests on wheat showed there was a wide range in the virulence of individual isolates. Field studies suggested that direct infection of wheat by ascosporic inoculum was unlikely, but that primary infection of ryegrass by ascospores was possible. Surveys showed that ryegrass was often infected with ergot and glasshouse tests proved that these isolates were able to infect wheat. This suggests that ergot survives from year to year on infected ryegrass and can pass to wheat by conidial transfer when conditions are favourable. The level of ergot contamination of grain was reduced to a negligible level by controlling ryegrass within a crop. Victorian wheat cultivars vary in their reactions to C. purpurea, the cultivars Kewell and Olympic being very susceptible to ergot while the cultivars Halberd, Zenith and Kalkee are moderately resistant. No cultivars tested have shown immunity. The results of these studies show ergot infection of wheat can be avoided by planting seed free of ergot, burning and deep ploughing of ergot infested land, controlling ryegrass within crops and the sowing of resistant cultivars