POSSIBLE ASSOCIATION OF PHYTOALEXINS WITH RESISTANCE GENE-EXPRESSION IN FLAX TO MELAMPSORA-LINI

Two antifungal compounds, coniferyl alcohol and coniferyl aldehyde, were isolated from facilitated dilusates of flax leaves inoculated with incompatible races of Melampsora lini. The two phenylpropanoid compounds accumulated more rapidly in all incompatible reactions than in compatible. In addition, the compounds accumulated more rapidly in resistance genotypes typified by rapid restriction of fungus growth and smaller lesions than in resistance genotypes typified by later restriction of fungus growth and larger lesion areas. Phloroglucinol stained incompatible infection sites, but not those of compatible sites, thus indicating that coniferyl aldehyde accumulation and perhaps induced lignification occurred in the incompatible sites. Initial detection of phloroglucinol-staining was chronologically correlated with the cessation of fungus growth and inversely correlated with ultimate lesion size. The evidence indicated that de novo production of coniferyl alcohol and coniferyl aldehyde may be the mechanism for restriction of fungus growth in incompatible flax leaves and that the phenylpropanoid compounds may represent phytoalexins effective against M. lini. © 1979.