Submitted to: Acta Horticulture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: July 17, 1996
Publication Date: N/A
Apples of high (Granny Smith; GS), moderate (Red Delicious; RD), and low (Gala; GA) susceptibility to superficial scald were stored for up to 4 months at 0C under high (100 percent) or low (1.5 percent) oxygen or in air. Hexane extracts of peel samples were analyzed for farnesene and its major oxidation product, a conjugated trienol, using an HPLC method which allows simultaneous detection at 232 and 269 nm, respectively. Their identity was confirmed by UV spectrometry, HPLC with diode array detection, and GC-MS. In general, farnesene and trienol content correlated with susceptibility to scald. Levels of both isoprenoids were over 20-fold higher in GS compared with GA, the latter having only trace amounts. Farnesene content peaked in both GS and RD at 2 months, whereas trienol continued to rise. Production of farnesene and trienol increased at higher oxygen levels in all three cultivars. The amount of trienol was more closely correlated with oxygen concentration. GS fruit stored under 100 percent oxygen were completely "bronzed" after 3 months and had a high level of ethanol. Two lots of RD fruit harvested 1 week apart differed markedly in their rate and extent of farnesene and trienol production, those from the earlier harvest having higher levels of both compounds at all times. Overall these results support the contention that susceptibility to scald in a given cultivar is a function of farnesene production and conjugated trienols are produced via autoxidation of farnesene.