Hypersensitive response in potato tuber: elicitation by combination of non-eliciting components from Phytophthora infestans

Abstract

Insoluble cell wall material and a lipid fraction from mycelia of Phytophthora infestans were found to be inactive, separately, as elicitors of the hypersensitive response in potato tuber discs. Recombination of the two materials, however, resulted in a mixture which was able to cause rishitin accumulation as well as necrosis in tuber tissue. The insoluble cell wall material was found to consist of predominately carbohydrate; hydrolysis yielded glucose as the major monosaccharide. Significant levels of protein were also found in the cell wall fraction which indicates that this material was not entirely glucan. The active component(s) of the P. infestans lipid material was found in the non-saponifiable fraction and was located by thin-layer chromatography. We suggest that eliciting material from P. infestans mycelial extracts requires components other than fungal glucans for activity on potato tuber tissue and describe a system which allows for further investigation of these components.