Studies on the resistance of Japanese pears to black spot disease fungus (Alternaria kikuchiana TANAKA). VI

Abstract

Phenoic compounds were separated with chromatographical and chemical techniques from extracts of Japanese pear tissue. And they were identified as arbutin, chlorogenic acid, chlorogenic acid isomers, caffeic acid, quinic acid, catechin and its isomer.The young leaf contained more amount of arbutin, caffeic acid and quinic acid than old one, but did not contain catechins. Much amount of chlorogenic acids were contained in the leaf without any distinction of its age.Infecting with host-specific toxin produce dby the fungus, the young leaf of susceptible variety (Nijusseiki) has been browned at a short time and decreased the content of arbutin and chlorogenic acid. On the other hand, the young leaf of resistant variety (Chojuro) remained green upon the same product treatment and no effect on the content of those phenolic compounds.Reacting the phenolic compounds with polyphenol oxidase extracted from the young leaf of susceptable variety, arbutin and chlorogenic acid were oxidized and browned immediately.So from above results, authors believed that arbutin and chlorogenic acid may have close contact with brown of the leaf infected with that metabolic product.