Activity of Host - deriyed Attractants and Their Related Com of Phytopathogenic Aphanomyces cochliOitles pounds toward the Zoospores

Eleven flayones, including cochliophi]in A and a chromone, were chemically prepared to determine the attracting activity for zoospores of Aphanoayees eochtioitles, a causative fungus ef spinach root rot. Analyses of the structure-activity relationship of each revea]ed a significant correlation between the zoospore attracting a ¢ tivity and the A-ring oxygenation at C-5 and C-7 in the fiavone skeleton. The relative attractancy ef four regio-isomers of IV-trans-feruloyl 4-O-methyldopamine, which was identified as a zoospore attractant specific to another host plant ( VIenopedium athum, was also examined.