PROHEXADIONE-CALCIUM INDUCES IN APPLE THE BIOSYNTHESIS OF LUTEOFOROL, A NOVEL FLAVAN 4-OL, WHICH IS ACTIVE AGAINST ERWINIA AMYLOVORA

Treatments with prohexadione-calcium lead to lower incidence of fire blight, scab and other diseases in pome fruit trees and other crop plants.
In addition to acting as a growth regulator, prohexadione-calcium interferes with flavonoid metabolism and induces the accumulation of the 3-deoxycatechin luteoliflavan, in shoots of pome fruit trees.
Luteoliflavan does not possess any remarkable antimicrobial activity.
Therefore, luteoforol, its unstable and highly reactive precursor, has been tested in vitro for its bactericidal and fungicidal activity.
Luteoforol was found to be highly active against different strains of Erwinia amylovora, the causal agent of fire blight, and all other bacterial and fungal organisms tested.
Its activity was more than 10-times higher than that of the structurally related phytoalexins luteolinidin and apigeninidin.
Phytotoxic effects were observed in pear plantlets.
These results indicate that prohexadione-calcium induces luteoforol as an active principle with non-specific biocidal properties.
It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue.

X International Workshop on Fire Blight

F. Spinelli, G. Costa, J.B. Speakman, W. Rademacher, H. Halbwirth, K. Stich

Acylcyclohexanediones, fire blight, induced resistance, Pantoea agglomerans, Pseudomonas fluorescens, Venturia inaequalis

https://doi.org/10.17660/ActaHortic.2006.704.32