First, second, and fifth authors: School of Agriculture, Nagoya University, Nagoya 464-8601, Japan; third and fourth authors: Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan
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Accepted for publication 11 January 2000.
An infection-inhibiting factor (IIF) was isolated from strawberry leaves and identified as (+)-catechin. This compound inhibited the formation of infection hyphae from appressoria of Alternaria alternata, but allowed both spore germination and appressorial formation. It is a normal component of strawberry leaves, but further accumulates as the major IIF in response to inoculation with nonpathogenic spores of A. alternata. The accumulation of (+)-catechin on a susceptible host was not induced, however, by inoculation with pathogenic spores of the strawberry pathotype or by inoculation with nonpathogenic spores supplemented with host-specific toxin (AF-toxin I). These results imply that (+)-catechin acts as a protective agent during induced resistance and that AF-toxin I acts as a fungal suppressor of induced resistance.
Alternaria black spot of strawberry.
© 2000 The American Phytopathological Society