2018 ASHS Annual Conference

Tree position, especially in larger canopies, can impact fruit maturity, ripeness, and quality potentially influencing every management decision throughout the cold chain. Our earlier reports reveal the extent to which metabolism is altered including areas as diverse as those directly associated with fruit quality, aroma, appearance, and cellular integrity at harvest and throughout storage. The current report focuses on a relatively novel group of freely extractable metabolites including hydroxycinnamoyl triterpenes (coumaryl triterpenes) as well as fatty acyl esters of hydroxyfarnesene (hydroxyfarnesene esters), hydroxycinnamoyl alcohols (p-coumaryl esters), and ursolic acid (ursolic esters). (7E,9E)-2,6,10-Trimethyl-2,7,9,11-dodecatetraen-6-ol (CTOL) and detected 16:0, 18:0, 18:1, and 18:2 CTOL esters were composed of 3 different hydroxyfarnesene head groups. Fatty acyl moieties p-coumaryl, ursolic, and amyrin esters ranged from 16:0 to 22:0. CTOL, hydroxyfarnesene esters, p-coumaryl, and ursolic esters were elevated in peel of external fruit. CTOL and 2 hydroxyfarnesene esters were only detectable beyond 3 months in storage and p-coumaryl and ursolic esters were detectable at harvest. Both classes increased with storage duration. Coumaryl triterpenes were higher in peel from internal fruit at harvest and did not increase with storage duration. The function of these metabolites is largely unknown but are thought to be primarily structural or functional as specialized monomers of cutin with potential antioxidative functions or even providing polar paths through the cuticle. However, the outcome of these differences may be as evident as fruit appearance where superficial scald only developed on external fruit and CTOL and hydroxyfarnesene ester levels were highest. These results warrant further study of conditions leading to metabolic differences and the impacts they may have on fruit quality.