Ionones and βIonylideneacetic Acids: Their Influence on Abscisic Acid Biosynthesis by Cercospora rosicola

Abstract

Several ionones and β-ionylideneacetic acids inhibited absicisic acid (ABA) biosynthesis in Cercospora rosicola at 100 μm. At lower concentrations, α-ionone, 1′,2′-dihydroxy-l′,2′-dihydro-β-ionone and 4′-keto-α-ionone enhanced ABA biosynthesis. Conversions of ionones by C. rosicola were identified by GC-MS as: α-ionone to 4′-keto-α-ionone, 4′-keto-α-ionol and dehydrovomifoliol; and 1′-hydroxy-α-ionone to dehydrovomifoliol. The oxidations of α-ionone and its analogs parallel those of the α-ionylideneacetic acids. The β-ionylideneacetic acids were generally oxidized to more polar forms. Metabolites identified by GC-MS were 3′-hydroxy-, 3′-keto- and 1′,2′-epoxy-1′,2′-dihydro-β-ionylideneacetic acids. The fungus rapidly metabolized most exogenous materials to more polar forms.