Toxicity and Metabolism of Exogenous α,β-Unsaturated Carbonyls in Potato (Solanum tuberosum L.) Tubers

A group of aliphatic alpha,beta-unsaturated carbonyl compounds was evaluated for their utility as inhibitors of sprout growth in stored potato tubers ( Solanum tuberosum L.). Nondormant tubers were treated with vapors of six 8-10-carbon compounds of this chemistry. Subsequent sprout growth at 16 degrees C (95% relative humidity) over ca. 3 months in storage was suppressed by all compounds in a concentration-dependent manner. The volatile metabolites produced by sprout and associated tuber tissues following treatment with 3-octen-2-one, 3-nonen-2-one, and 3-decen-2-one were the corresponding alkyl ketones and alkyl secondary alcohols. In contrast, (E)-2-octenal, (E)-2-nonenal, and (E)-2-decenal were metabolized by two pathways: (1) parent compound to the corresponding alkyl aldehyde and then to the alkyl primary alcohol and (2) parent compound to the alkenyl primary alcohol. Residues of 3-nonen-2-one and (E)-2-nonenal and their metabolites were analyzed in whole tubers over a 28 day post-treatment period. The concentrations of the parent ketone and aldehyde declined rapidly following application, and the most persistent metabolites were 2-nonanol and (E)-2-nonen-1-ol, respectively. The sequence of reactions leading from the alpha,beta-unsaturated carbonyls to the alcohols was determined by application of each of the 9-carbon compounds individually to tubers. In long-term efficacy studies, a single application of (E)-2-nonenal and 3-nonen-2-one to nondormant tubers terminated sprout growth and prevented regrowth for 2-3 months. A second application suppressed sprouting for at least 4-5 additional months. This efficacy, combined with rapid metabolism and low residue levels, makes the 8-10-carbon alpha,beta-unsaturated ketones and aldehydes worth consideration for use as sprout inhibitors.