Of seven phenolic compounds, flavone(25ppm) showed the most suppressive effect on mycelial growth of Botryosphaeria dothidea followed by catechol (100ppm), and the other phenolic compounds did not inhibit the mycelial growth of the fungus.
The infected fruits gave higher contents of total phenols compared with the healthy fruit in Fuji cultivar, suggesting that phenols involve in disease resistance.
The contents of phenolic compounds of flavone, catechol, and cinnamic acid in fruit skin of Jonathan were higher than those of Fuji. However, coumaric acid, chlorogenic acid, and epicatechin did not give any differences in their contents in two apple cultivars. The contents of all the six phenolic compounds decreased rapidly at the end of the growing season.
Flavone injection with 100ppm to the Fuji apple trunk repeating four times from June to September, brought about an increment of flavone content in the fruit skin and resulted in reduction of rot infection compared with the fruit on non-treated trees, without giving any detrimental effect to the fruit quality.
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