Purification and properties of suppressor glucan isolated from Phytophthora infestans.

Abstract

The glucan was isolated from fungal homogenates of the potato blight fungus and purified by HPLC. The active glucan fraction from both compatible and incompatible races consists of 2 components, Mr 4700 and 280. Suppressor activity was analysed by phytoalexin accumulation as a biochemical marker of the hypersensitive reaction of potato tuber cells. The partially purified preparations showed suppressor activity at 25-50 æg/disc (14 mm diam.), whereas the purified components (Mr 4700 and 280) from the 2 races showed little significant difference in inhibition of phytoalexin accumulation at the same concn. HPLC analysis of germination fluid of P. infestans demonstrated that the fungus produced suppressor glucan with Mr 280 and 30 000 at an early stage of infection. These results suggest that the 2 components of the purified suppressor had little race specific activity, and that the specific suppressor activity occurred when other components of the glucan existed. The component with Mr 280 had a close Rf value to that of glucose monomer in thin-layer chromatography assay.