Effect of dioxygenase inhibitors on the resistance-related flavonoid metabolism of apple and pears: Chemical, biochemical and molecular biological aspects

The plant growth regulator prohexadione-Ca, which is an inhibitor of 2-oxoglutarate dependent dioxygenases, acts as an anti-gibberellin and also reduces fire blight and scab of apple and pear. This beneficial side effect is related to a transient alteration of the flavonoid metabolism in apple and pear target tissues. This paper reviews the changes of the composition of flavonoids and phenylpropanoids occurring in leaves treated with prohexadione-Ca. An alternative flavonoid pathway is described leading to the formation of 3-deoxycatechins, which are uncommon in apple and pear. As biochemical prerequisites for this change in metabolism the substrate specificity of key enzymes is demonstrated.