Ontogenetic variation of catechin biosynthesis as basis for infection and quiescence of Botrytis cinerea in developing strawberry fruits

The accumulation of catechin derived procyanidins is regarded as one fundamental factor inhibiting the growth of the pathogenic fungus Botrytis cinerea in immature strawberry fruits - a phenomenon referred to as quiescence after invasion at bloom usually ending during fruit ripening. For evaluation of that hypothesis an attempt was made to modify the concentration of flavanols in developing strawberry fruits by treatments with an inhibitor of 2-oxoglutarate-dependent dioxygenases which is known to affect the flavonoid pathway. The accumulation of novel flavonoids identified as luteoliflavan and eriodictyol 7-glucoside and enhanced levels of catechin were found when green fruits were treated. The effect of the bioregulator varies during fruit ontogenesis with a steady increase after flowering to the stage of small green fruits and a rapid decrease thereafter. It became obvious that young fruits just at flowering do not accumulate flavanols to a sufficient level for preventing primary receptacle infection.