Flavor composition of transgenic raspberry bushy dwarf virus-resistant 'Meeker' raspberries

Graduation date: 2008Raspberries have been popular since the time of the ancient Greeks. Red raspberries are cultivated throughout the world, particularly in the Pacific Northwest region of the United States and Canada. The raspberry bushy dwarf virus (RBDV) causes significant reduction in yield and crumbly fruit in raspberries, blackberries and raspberry-blackberry hybrids. There is no effective treatment once a plant is infected and the only effective prevention is using resistant varieties. Resistance is difficult to attain using traditional cultivation techniques. Through transgenic modification, five lines of resistant red raspberries have been developed from the 'Meeker' cultivar. To investigate trueness to type, flavor characteristics for raspberries grown in Oregon and Washington during 2004 and 2005 were compared. Aroma volatiles important to the raspberry aroma profile were quantified, as well as the sugar and organic acid profiles, to compare the five transgenic 'Meeker' lines with the wild\ud type 'Meeker', 'Chilliwack', 'Tulameen', 'Willamette' and 'Yellow Meeker'.\ud Thirty aroma compounds ((Z)-3-hexenol, 4-isopropylbenzyl alcohol, 6-\ud methyl-5-hepten-2-ol, 2-nonanol, hexanal, (E)-2-hexenal, (Z)-3-hexenyl acetate,\ud ethyl hexanoate, methyl nonanoate, 2-heptanone, 2-nonanone, raspberry ketone,\ud zingerone, δ-octalactone, δ-decalactone, para-cymene, geraniol, α-ionone, β-ionone,\ud limonene, linalool, myrcene, nerol, α-phellandrene, α-pinene, sabinene, α-terpinene, γ-terpinene, α-terpineol, terpinen-4-ol and terpinolene) were selected and quantified using stir bar sorptive extraction (SBSE) paired with gas chromatography-mass spectrometry (GC-MS) in all raspberry samples. The chiral stereoisomers of some volatile compounds in these raspberries were also studied using a cyclosilB GC column. Different raspberry cultivars varied widely in titratable acidity, sugar and acid concentration, and volatile composition, particularly α-ionone, linalool and (Z)-3-hexenol. Chiral compositions were also quite different among the cultivars studied. For the wild type 'Meeker' and RBDV-resistant varieties, flavor variations were observed from sites to sites and year to year. However, overall volatile profile had much less variations compared with sugar and organic acid profiles. None of the analyses separated the transgenic 'Meeker' raspberries from the wild type 'Meeker', and result was consistent for both of the locations and years studied. The results suggested that the transgenic RBDV-resistant 'Meeker' varieties were not different from the wild type 'Meeker' raspberry