Plants generate protective molecules in response to ultraviolet (UV) light. In laboratory experiments, 48 h UV-B irradiation of peach fruits and leaves reduced the flavour-related monoterpene linalool by 60%. No isoprene was detected, but other terpenoids increased significantly, including a threefold accumulation of the sesquiterpene (E,E)-α-farnesene, which was also increased by jasmonic acid treatment. RNA sequencing revealed altered transcript levels for two terpene synthases (TPSs): PpTPS1, a TPS-g subfamily member, decreased by 86% and PpTPS2, a TPS-b subfamily member, increased 80-fold. Heterologous expression in Escherichia coli and transient overexpression in tobacco and peach fruits showed PpTPS1 was localized in plastids and associated with production of linalool, while PpTPS2 was responsible for (E,E)-α-farnesene biosynthesis in the cytoplasm. Candidate regulatory genes for these responses were identified. Commercial peach production in Asia involves fruit bagging to maintain marketable yield and quality. TPS gene expression and volatile terpenoid production in field experiments, using bags transmitting high UV-B radiation, showed similar effects on peach volatiles to those from laboratory experiments. Bags transmitting less UV-B light ameliorated the reduction in the flavour volatile linalool, indicating that flavour components of peach fruits can be modulated by selecting an appropriate source of environmental screening material.

First purchases of fruit are mainly dependent on aspects of appearance such as color. However, repeat buys of fruit are determined by internal quality traits such as flavor-related volatiles. Differences in volatile profiles in white- and red-fleshed peach fruit are not well understood. In the present study, peach cultivars with white- and red-fleshed fruit were subjected to sensory analysis using electronic nose (e-nose) to evaluate overview volatile profiles. Approximately 97.3% of the total variation in peach color-volatiles was explained by the first principle component 1 (PC1) and PC2. After analyzing sensory differences between peach fruit samples, 50 volatile compounds were characterized based on GC-MS. Multivariate analysis such as partial least squares discriminant analysis (PLS-DA) was applied to identify volatile compounds that contribute to difference in white- and red-fleshed peach fruit cultivars. A total of 18 volatiles that could separate peach fruit cultivars with different colors in flesh during ripening were identified based on variable importance in projection (VIP) score. Fruity note latone γ-hexalactone had higher contents in red-fleshed cultivars, while grassy note C6 compounds such as hexanal, 2-hexenal, (E)-2-hexenal, 1-hexanol, and (Z)-2-hexen-1-ol showed great accumulation in white-fleshed peach fruit.