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Title: Oxidation products of alpha-farnesene associated with superficial scald development in d'Anjou pear fruit are conjugated trienols

Author
item Whitaker, Bruce

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2007
Publication Date: 5/2/2007
Citation: Whitaker, B.D. 2007. Oxidation products of alpha-farnesene associated with superficial scald development in d'Anjou pear fruit are conjugated trienols. Journal of Agricultural and Food Chemistry. 55:3708-3712.

Interpretive Summary: A storage disorder called superficial scald occurs in a number of popular varieties of apples and pears. Scald appears as sunken brown patches on the skin that make the fruit unmarketable, resulting in large economic loss. This study was conducted to find if scald development in pears and apples involves the same biochemical mechanism. Toxic oxidation products of the natural compound alpha-farnesene called conjugated trienols (CTols) are thought to cause scald in apples, and it was found that high levels of CTols accumulate in the skin of scald-prone d’Anjou pears during cold storage. Further work will determine whether a specific enzyme is responsible for production of CTols in both apples and pears. If so, the enzyme could be a target for genetic manipulation to block CTol accumulation. This research provided information that can be used by plant scientists to develop new scald-resistant varieties of apple and pear fruits, which will no longer require a chemical drench treatment to control scald.

Technical Abstract: Conjugated triene (CT) oxidation products of the acyclic sesquiterpene alpha-farnesene are thought to induce development of the physiological storage disorder superficial scald in apple and pear fruits of susceptible cultivars. CTs that accumulate in peel tissue of Granny Smith and Delicious apples after several weeks of cold storage are known to be conjugated trienols (CTols) rather than the corresponding hydroperoxides produced by in vitro autoxidation of a-farnesene. Here it is shown that CTols are also the predominant in vivo oxidation products of a-farnesene in cold-stored pear fruit of the highly scald-susceptible d’Anjou cultivar. Analysis by C18-HPLC-DAD, GC-FID, GC-MS, and proton NMR identified 3,7,11-trimethyldodeca-1,3(E),5(E),10-tetraen-7-ol as the major CT in hexane extracts of peel tissue from d’Anjou pears stored 3–5 months in air at -1 C. The possible origins of CTols in apples and pears, and the hypothesized role of these oxidation products of a-farnesene in the induction of scald, are discussed.