Abstract
Quinic, prephenic, phenylpyruvic, trans-cinnamic, p-coumaric, and caffeic acids were identified by gas-liquid chromatography in the root extract of Japanese radish infected by Peronospora parasitica. Ferulic and sinapic acids were not detected. These phenolic acids detected did not originate from the infecting hyphae but from the host cells. These phenolic acids were not detected in the healthy root. Since the phenolic acids are considered to be precursors of lignin, the relationship between the phenolic acids detected and lignin formation in the infected plants was discussed.
