Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2014
Publication Date: 10/1/2014
Citation: Bai, J., Baldwin, E.A., Hearn, J., Driggers, R.E., Stover, E.W. 2014. Volatile Profile Comparison of USDA Sweet Orange-like Hybrids versus ‘Hamlin’ and ‘Ambersweet’. HortScience. 49(10):1262-1267. Interpretive Summary: Six early season hybrids that are sweet-orange-like in fruit size, color, and taste were analyzed for volatile profiles by using a combination of headspace solid phase microextraction (SPME) sampling technology and gas chromatography–mass spectrometry (GC-MS) analytical methods. Cluster and principle component analysis (PCA) analysis based on 135 volatile compounds support the classification of the hybrids as sweet orange - the hybrids are similar to commercial sweet orange in the juice flavor.
Technical Abstract: Six orange hybrids, formed by crossing ‘Ambersweet’, a hybrid classified as sweet orange, with one of three different hybrids, were selected for fruit size, color, and taste as potential new sweet orange cultivars. The objective of this research was to analyze the volatile profiles of these hybrids for comparison with ‘Ambersweet’, one of the parents, and ‘Hamlin’, the most widely grown early sweet orange in Florida. All hybrids are at least ½ sweet orange and varying amounts of mandarin, grapefruit, Poncirus trifoliata, and sour orange in each pedigree. In total, 135 volatiles were detected in the 8 hybrid lines/commercial cultivars over two harvests, and 20 compounds were detected in all samples, including terpenes (limonene, ß-myrcene, a-pinene, a-terpinene, a-terpineol and linalool), esters (ethyl butanote, ethyl pentanoate and ethyl acetate), aldehydes (acetaldehyde, hexanal, and nonanal) and alcohols (ethanol and hexanol). Total abundance of volatiles in January-harvested fruits averaged 30% higher than for fruits of the same trees harvested in November. ‘Ambersweet’ contained the highest total amount of volatiles (mainly due to very high levels of monoterpenes), and of them, nootkatone, and six other compounds were not detected in any of the hybrids, and some of them were also not detected in ‘Hamlin’. On the other hand, 12 compounds, including pentanal, ethyl 2-butenoate, and ethyl nonanoate were not detected in ‘Ambersweet’, but were found in ‘Hamlin’ and some of the hybrids. Cluster analysis separated the cultivar/hybrid and harvest time combinations to three clusters. FF-1-76-50, FF-1-76-52 and January FF-1-75-55, all with the same parents (‘Ambersweet’ x FF-1-30-52) were close to FF-1-65-55, but they were separated from ‘Hamlin’ and further separated from ‘Ambersweet’. The cluster containing ‘Hamlin’ has three subclusters: January ‘Hamlin’ and November FF-1-74-14, a hybrid with 1/8 P. trifoliata, which includes a slight off-flavor frequently found in P. trifoliata hybrids, independent to each other and both were separated from a group of November ‘Hamlin’, FF-1-64-97 and FF-1-75-55. The cluster containing ‘Ambersweet’ included January FF-1-64-97. A principle component analysis (PCA) separated ‘Ambersweet’ from all hybrids and ‘Hamlin’ along the PC 1 axis and separated November harvests from January harvests along PC 2. This volatile analysis supports the classification of the hybrids as sweet orange.