high grape stilbenoid concentration over time, similar to that achieved by postharvest
UV-C light treatment, but its maximal effects can be observed sooner, 24 h after each
daily treatment. The variability of this UVC preharvest treatment regarding grape
variety and season has not been studied yet, but it is expected to be highly variable.
2.3
Combination of Elicitors: Preharvest Treatment with MEJA
Plus Postharvest UVC Treatment
All the above stresses or their combinations can be used to target increases in healthpromoting stilbenes. A synergistic effect on phytoalexin production has been described
between MEJA and ethephon [59], CHIT and UVC [33, 60], MEJA and UVC [33, 61],
BTH and UVC [33], and MEJA and cyclodextrins [62, 63], among others [28].
Treatments with MEJA and UVC have been studied in Vitis vinifera L. cv.
suspension cultures of Cabernet Sauvignon cells [64]. Both treatments improved
both the production of stilbene within the cells and the accumulation of transresveratrol in the culture medium. UV-C irradiation for 20 min or MEJA at
100 μM was efficient in promoting stilbene accumulation. The combined treatment
of UV-C and MEJA highly induced the production of total intracellular stilbene
at the maximum of 2005.05 Æ 63.03 μg g
À1 dw and showed a synergistic effect on
the accumulation of extracellular trans-resveratrol at 3.96 Æ 0.2 mg l
À1 .
From the above combinations, the preharvest MEJA + postharvest UVC treatments can be proposed as a promising treatment to increase the stilbene content in
grapes [33]. Syrah grapevines were sprayed with MEJA (10 mM in ethanol) three
times (20, 16, and 13 days before harvesting). A control was also treated with
ethanol at the same time. Once ripeness was reached, grapes from both the treated
grapevine and its respective control were harvested and UVC treated (Fig. 5).
An increase in trans-resveratrol, piceatannol, and ε-and δ-viniferin content was
observed in all the treated grapes, especially in the MEJA+UVC ones. Although
the grape stilbene concentration reached with the MEJA-UVC combination did not
exceed that reached by UVC alone, the storage period required after treatment to
reach the maximum resveratrol concentration (Dm) was reduced by 3 days. This is
an important finding because it demonstrates that the combination of MEJA with
UVC accelerated stilbene biosynthesis, which is linked to the preservation of grape
quality. Therefore, the MEJA-UVC treatment is suggested as an interesting application for stilbene-enriched grape production [33].
3
Stilbene-Enriched Wines
Numerous epidemiological studies have shown that long-term moderate consumption of wine is linked to a lower level of cardiovascular illnesses. A study conducted
by Renaud and de Lorgeril [65] revealed that the incidence of coronary heart disease
in France is about 40% lower than in the rest of Europe; this was termed the “French
paradox,” which appeared to be related to regular consumption of red wine.
26 Preharvest Methyl Jasmonate and Postharvest UVC Treatments: Increasing. . .
633
UV-C light treatment, but its maximal effects can be observed sooner, 24 h after each
daily treatment. The variability of this UVC preharvest treatment regarding grape
variety and season has not been studied yet, but it is expected to be highly variable.
2.3
Combination of Elicitors: Preharvest Treatment with MEJA
Plus Postharvest UVC Treatment
All the above stresses or their combinations can be used to target increases in healthpromoting stilbenes. A synergistic effect on phytoalexin production has been described
between MEJA and ethephon [59], CHIT and UVC [33, 60], MEJA and UVC [33, 61],
BTH and UVC [33], and MEJA and cyclodextrins [62, 63], among others [28].
Treatments with MEJA and UVC have been studied in Vitis vinifera L. cv.
suspension cultures of Cabernet Sauvignon cells [64]. Both treatments improved
both the production of stilbene within the cells and the accumulation of transresveratrol in the culture medium. UV-C irradiation for 20 min or MEJA at
100 μM was efficient in promoting stilbene accumulation. The combined treatment
of UV-C and MEJA highly induced the production of total intracellular stilbene
at the maximum of 2005.05 Æ 63.03 μg g
À1 dw and showed a synergistic effect on
the accumulation of extracellular trans-resveratrol at 3.96 Æ 0.2 mg l
À1 .
From the above combinations, the preharvest MEJA + postharvest UVC treatments can be proposed as a promising treatment to increase the stilbene content in
grapes [33]. Syrah grapevines were sprayed with MEJA (10 mM in ethanol) three
times (20, 16, and 13 days before harvesting). A control was also treated with
ethanol at the same time. Once ripeness was reached, grapes from both the treated
grapevine and its respective control were harvested and UVC treated (Fig. 5).
An increase in trans-resveratrol, piceatannol, and ε-and δ-viniferin content was
observed in all the treated grapes, especially in the MEJA+UVC ones. Although
the grape stilbene concentration reached with the MEJA-UVC combination did not
exceed that reached by UVC alone, the storage period required after treatment to
reach the maximum resveratrol concentration (Dm) was reduced by 3 days. This is
an important finding because it demonstrates that the combination of MEJA with
UVC accelerated stilbene biosynthesis, which is linked to the preservation of grape
quality. Therefore, the MEJA-UVC treatment is suggested as an interesting application for stilbene-enriched grape production [33].
3
Stilbene-Enriched Wines
Numerous epidemiological studies have shown that long-term moderate consumption of wine is linked to a lower level of cardiovascular illnesses. A study conducted
by Renaud and de Lorgeril [65] revealed that the incidence of coronary heart disease
in France is about 40% lower than in the rest of Europe; this was termed the “French
paradox,” which appeared to be related to regular consumption of red wine.
26 Preharvest Methyl Jasmonate and Postharvest UVC Treatments: Increasing. . .
633