The interaction of some phytopathogenic fungi with plant tissue

The phytoalexin test of Müller was applied to various host/parasite combinations. The highest production was obtained when spores ofSclerotinia fructicola were on slices of potato tuber, and spores ofColletotrichum lindemuthianum in contact with bean pod tissue. During the period of incubation of the fungus on the host plant tissue substances were formed or excreted by the plant tissue. Several amino acids and carbohydrates (saccharose, glucose and fructose) could be demonstrated by paper chromatography. Most of these substances were found at much higher concentrations in the controls (i.e. drops of double distilled water incubated upon host tissue), than in the supernatant of the spore suspension after the incubation period. Drops of spore suspension and drops of double distilled water on glass cavity slides never contained these substances, or they were in such low concentrations as to be undetectable by paper chromatography. Inhibition of spore germination by a phenolic compound was not confirmed in the used test objects and host/parasite combinations.