Roˆle of antimicrobial substances (tuliposides) in tulips attacked by Botrytis spp.

Abstract

The function of preformed substances in tulips, so-called tuliposides, in disease resistance was examined. As an example, the host-parasite relationships between tulips and Botrytis cinerea and Botrytis tulipae, respectively, were studied. Botrytis tulipae and Botrytis cinerea caused a release of tuliposides from both attached and detached pistils by increasing the permeability of cell membranes. Botrytis cinerea caused an essentially higher increase in permeability. Under the influence of Botrytis cinerea the tuliposides were converted into lactones with a high biological activity. Botrytis tulipae, on the contrary, caused a cleavage of the tuliposides into the corresponding acids with a very low biological activity. Botrytis cinerea was more sensitive to the inhibitory substances than Botrytis tulipae. It is argued that for these reasons Botrytis cinerea could not infect tulips, but that Botrytis tulipae could overcome the barrier of the inhibitory substances.