Volatile compounds in the peel and flesh of cucumber (Cucumis sativus L.) grafted onto bottle gourd (Lagenaria siceraria) rootstocks

The objective of this study was to investigate the distribution of volatile organic compounds (VOCs) in the peel and flesh of the cucumber (Cucumis sativus L.) cultivar 'Cengelkoy' grafted onto different bottle gourd rootstocks, as VOCs play an essential role in fruit quality. Three genotypes of bottle gourd (Lagenaria siceraria; '33-35', '33-41' and '46-03') were chosen as being representative of Turkish bottle gourd germplasm. The VOCs in each rootstock-scion combination were analysed using carboxen-divinylbenzene-polydimethylsiloxane fibres for solid-phase micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The VOCs (Z)-6-nonenol (21.4 - 28.6%), (E,Z)-2,6-nonadienol (3.2 - 13.0%), (E,Z)-3,6-nonadienol (1.9 - 7.1%), 1-nonanol (4.9 - 7.2%), (E)-2-nonenal (3.9 - 6.6%), (E,Z)-2,4-heptadienal (5.7 - 6.9%), (Z)-6-nonenal (3.6 - 5.4%), (E)-2-hexenal (0.9 - 4.4%), (E,E)-3,5-octadien-2-one (3.2 - 3.5%), and hexanal (1.9 - 3.6%) were the most abundant compounds found in cucumber peel. Grafting had a significant (P <= 0.05) effect on the percentage composition of the major VOCs in peel. (E,Z)-2,6-Nonadienal (34.3 - 41.5%), (E)-2-nonenal (15.5 - 19.9%), (Z)-6-nonenal (5.9 - 8.0%), (Z,Z)-3,6-nonadienol (2.6 - 8.4%), (Z)-6-nonenol (2.7 - 7.9%), 3-decyne (2.1 - 3.4%), and (E,Z)-2,6-nonadienol (1.9 - 5.7%) were the most significant volatiles in cucumber flesh. Of these compounds, (E,Z)-2,4-heptadienal, (E,E)-3,5-octadien-2-one, and 3-decyne were identified as cucumber VOCs for the first time. The results showed that the percentage composition of VOCs in the peel and flesh of cucumbers grafted onto bottle gourd '33-41' were closest to those in ungrafted control cucumber, 'Cengelkoy'. Therefore, Turkish bottle gourd genotype '33-41' has high potential as a rootstock for cucumer grafting.