PHYTOALEXIN ACCUMULATION IN SORGHUM - IDENTIFICATION OF AN APIGENINIDIN ACYL ESTER

The accumulation of a new 3-deoxyanthocyanidin phytoalexin in sorghum leaves and mesocotyls was demonstrated to occur following inoculation with an isolate of Colletotrichum graminicola pathogenic to sorghum, an isolate of C. graminicola pathogenic only to corn, and an isolate of Helminthosporum maydis (a nonpathogen of sorghum). The compound was found to be a caffeic acid ester of arabinosyl-5-O-apigeninidin and was never present in uninoculated tissues. Comparison of the fungitoxicity of the compound with that of two phytoalexins identified previously (apigeninidin and luteolinidin) showed that all three of the compounds exhibited toxicity to C. graminicola at concentrations of less than 10 μm. © 1990.