INDUCTION OF RESISTANCE IN BARLEY AGAINST ERYSIPHE-GRAMINIS F-SP HORDEI BY FREE CUTIN MONOMERS

Enzymatic degradation of plant cuticles at sites of fungal attack may release free cutin monomers. The hypothesis that free cutin monomers a re signals for the activation of plant defence reactions was tested in the interaction of barley with the fungal pathogen Erysiphe graminis f.sp hordei. Topical spray application of cutin monomers partially pro tected leaves of a highly susceptible barley cultivar against E. grami nis, the plants being challenge-inoculated 1-3 days after the applicat ion. The degree of protection obtained by the C18 family of cutin mono mers equaled protection obtained by the biological inducer E. graminis f.sp. tritici. Microscopic inspection of infection sites indicated en hanced resistance in barley epidermal cells to fungal penetration. Alt hough the cutin monomers tested did not induce a number of defence-rel ated barley genes, protection was eliminated by inhibiting host transc ription with cordycepin, suggesting the involvement of inducible host reactions in the observed protection. Two-dimensional display of in vi tro translation products from barley mRNA revealed the accumulation of one cutin monomer-induced mRNA, the same mRNA also being induced by p athogen attack. The data are compatible with a model that includes cut in monomers as signal molecules for the induction of disease resistanc e in barley. (C) 1996 Academic Press Limited