acknowledge Constellation Brands for supporting the project and providing the grapes used in this study. Figure 4: Free monoterpenes at harvest in field-grown ...
Irrigation Management for Improving the Ripening and Aromatic Contents in White Grapes in the Okanagan Valley Yevgen KOVALENKO, Marie NOSTEN, Simone CASTELLARIN Wine Research Centre, University of British Columbia, Vancouver, BC
Results
Nerol
Linalool
*** * **
* *
C
D
Cluster Weight (kg cluster-1)
Primary Leaf Area Index (m2 m-2)
*
*
a b
*
b
0.10
1.0
D
b
2.0
* 1.0
Conclusions
Free Monoterpenes at Harvest α-Farnesene
β-citronellol
α-Pinene
β-linalool
β-trans-Ocimene
β-myrcene
Total Terpene Content
3 Carene
60 500 40
ab 20
b
a
b
b
b
a
b
a
b
ab
400
b
0
300 Neric Acid
L-Limonene
Citronellyl Formate
Nerol
300
60
a ab ab
b
200
200
40 20
Methyl Geranate
Geraniol
Cis-Rose-Oxide
b
a
b
b
a b ab
b
a a ab
b
100
a ab
0
0
100
b
c 0
Berry Sugars ( OBrix)
*
Bound Monoterpenes at Harvest
* *
Figure 3: Evolution of (A) photosynthesis, (B) transpiration, (C) primary leaf area, and (D) secondary leaf area in CN, ED, LD, and PD vines. (E and F) Mean cluster weight at harvest and mean pruning weights. The dotted line indicates the beginning of deficit irrigation application (18 DAA). The dashed line indicates the onset of ripening, the initiation of late deficit irrigation application, and the end of early deficit irrigation (66 DAA). The solid line indicates harvest (98 DAA). Bars represent ± SE. Asterisks denote statistical significance between treatments (One-way ANOVA, p < 0.05). The lowercase letters denote statistical significance between treatments (One-way ANOVA and post-hoc Tukey’s HSD, , p < 0.05).
F
Figure 4: Free monoterpenes at harvest in field-grown Gewürztraminer, semi-quantified by HS-SPMEGC-MS with d3-linalool as internal standard. The lower-case letters denote statistical significance between treatments (One-way ANOVA and post-hoc Tukey’s HSD, p < 0.05).
E Titratable Acids (g L-1)
* * * *
*
Figure 1: Principle Gewürztraminer-specific Monoteperene Flavour Compounds
Experiments were conducted on 7-year old field-grown Vitis vinifera L. cv. Gewürztraminer Clone 47 grafted on 3309 rootstock planted in N-S rows at an approximate density of 3,333 vines hec-1 in the southern Okanagan Valley, near Oliver, British Columbia (49°14'N, 119°33'W, 420 m a.s.l.). Four irrigation treatments were replicated on four plots arranged in a randomized block design. Sampling occurred every 7 – 14 days starting 18 DAA (June 22, 2016 to September 10, 2016), collecting 40 to 80 berries for sugar, acid, and monoterpene analysis. In order to characterize the impact of the treatments on vine physiology, leaf water potential was monitored using the Scholander pressure chamber at ± 1 h from solar noon. Gas exchange parameters were monitored using a LI-COR 6400 gas exchange system at + 1 – 3 h from sunrise. Leaf area was also assessed throughout the season. Yield was measured at harvest and pruning weights were measured in the winter following the growing season. Free and bound volatiles were quantified through HSSPME and LI GC-MS.
* * *
E
*
Rose Oxide
Methods
* *
B
**
0.20
C
Pruning Weight (kg vine-1)
*
Transpiration Rate (mmol H2O m-2 s-1)
**
**
A
Photosynthesis (µmol CO2 m-2 s-1)
Rainfall Volume (L vine-1)
Temperature (OC) Ψleaf ( MPa)
*
D3-Linalool Equivalents (ng g-1 berry)
Citronellol
B
D3-Linalool Equivalents (ng g-1 berry)
Geraniol
Figure 2: (A) Rainfall and mean temperature in 2016. Evolution of (B) Ψleaf , (C) berry weight, (D) berry sugars, and (E) berry acids in CN, ED, LD, and PD vines. The dotted line indicates the beginning of deficit irrigation application (18 DAA). The dashed line indicates the onset of ripening, the initiation of late deficit irrigation application, and the end of early deficit irrigation (66 DAA). The solid line indicates harvest (98 DAA). Bars represent ± SE. Asterisks denote statistical significance among treatments (One-way ANOVA, p < 0.05)
A
(in g berry WeightWeight Berry Berry (g) -1)
Gewürztraminer is the sixth most widely growth grape in the Okanagan and third most grown white grape. Gewürztraminer is considered an aromatic white-wine cultivar since it accumulates a remarkable amount of monoterpenes. Some of these compounds, such as geraniol, nerol, rose oxide, linalool, and citronellol (see Figure 1), are of particular interest because their presence or absence affects the cultivar-specific sensory profile of Gewürztraminer grapes and wines. These compounds are subject to modulation by the plant in response to biotic and abiotic stresses as well as viticultural practices. Deficit irrigation is a viticultural practice that applies a controlled stress to the vine and it is often used in red grape varieties to improve grape and wine quality; however, little work has been done with white grapes particularly in the Okanagan Valley. The timing of deficit irrigation application is also known to alter the effectiveness of the treatment. In this study, Gewürztraminer vines were grown under three irrigation treatments: wellwatered (Control, CN), water deficit applied pre-véraison (Early Deficit, ED); water deficit applied post-véraison (Late Deficit, LD), and water deficit applied from pre-véraison to harvest (Prolonged Deficit, PD). The hypothesis is that application of deficit irrigation can induce the synthesis of monoterpenes with pre-véraison and prolonged application of water deficit being most effective than later application. The goal of this project is optimize Gewürztraminer grape quality through targeted irrigation practices.
Secondary Leaf Area Index (m2 m-2)
Introduction
1. Deficit irrigation negatively impacted berry sugar accumulation, and berry and cluster weight. PD demonstrated most severe reduction, while ED and LD were similar in effect. 2. Total free terpene content was unaffected in response to deficit irrigation, however, significant changes were observed in the terpene profiles among treatments. LD appears to effect terpene profile more than other treatments. 3. Deficit irrigation positively impacted certain bound terpenes in the profile, despite total content being unaffected. PD was observed to have the largest effect size.
Total Terpene Content
a
a
ab
ab
ab
ab
b
b a
ab
ab
b
Figure 5: Bound monoterpenes at harvest in field-grown Gewürztraminer, semi-quantified by HSSPME-GC-MS with d3-linalool as internal standard. The lower-case letters denote statistical significance between treatments (One-way ANOVA and post-hoc Tukey’s HSD, p < 0.05).
Future Direction 1. Complete volatile analysis for the entire 2016 growing season. 2. Volatile-analysis informed gene expression analysis using qPCR. 3. Repetition of the experiment during the 2017 season in order to assess consistency of the treatment effects between seasons.
Acknowledgements: We are grateful to the funding support provided by BC Wine Grape Council, MITACS, NSERC, and BC Investment Agriculture Foundation. We also acknowledge Constellation Brands for supporting the project and providing the grapes used in this study.
