Gómez-Alonso and García-Romero
Irrigation, variety and grape d18O and d13C values
283
Effect of irrigation and variety on oxygen (d18O) and carbon
(d13C) stable isotope composition of grapes cultivated
in a warm climate
S. GÓMEZ-ALONSO and E. GARCÍA-ROMERO
Instituto de la Vid y el Vino de Castilla-La Mancha, Ctra Toledo-Albacete s/n, CP 13700 Tomelloso,
(Ciudad Real) Spain
Corresponding author: Dr. Sergio Gómez-Alonso, fax + 34 926512610, email [email protected]
Abstract
Background and Aims: d13C values from Vitis vinifera leaves, whole grape, seed, pulp, skin and/or grape
must sugars have been investigated as an integrated marker of vine water status or intrinsic water-use
efficiency during berry growth and across region of origin, vintage and variety. The use of 18O/16O isotopic
ratio as a marker of water addition, vintage and geographical origin has also been studied. This paper
examines the effect of irrigation and grapevine variety on d18O and d13C of grape must from eight varieties,
all cultivated in the same vineyard to reduce the effects from other variables.
Methods and Results: Stable isotope compositions of grape must water and sugar were determined by
isotope ratio mass spectrometry. The result of the study showed statistically significant effects of irrigation
and vine variety on both d18O and d13C. The effect of vintage on d18O was only significant for non-irrigated
vines.
Conclusion: This research highlights the effect of variety and irrigation on d13C and d18O of grape.
Significance of the Study: This is the first report to demonstrate that the varietal effect on d13C and
d18O of grape is not due only to differences in the vegetative cycle of each variety. It further suggests that
water exhibits a lower isotopic discrimination in the indigenous Spanish varieties studied than in
non-indigenous varieties.
Abbreviations
DI drought index; IRMS isotope ratio mass spectrometry.
Keywords: carbon, grape, irrigation, oxygen, stable isotope, Vitis vinifera L.
Introduction
Light isotope forms of compounds containing elements
like carbon, hydrogen, nitrogen and oxygen are more
volatile, more reactive, are distributed faster and are
quicker to take part in natural biochemical reactions. As a
result, isotopic differentiation occurs during physical and
biological processes, making it possible to use certain isotopic ratios as authenticity markers for biological and
chemical samples (origin, identity, adulteration, drug
taking, etc.).
Because of photosynthetic differences, C3 plants like
vines contain less 13C than C4 plants like corn or sugarcane (Farquhar et al. 1989). Because of this, must sugar
or wine ethanol d13C values can be used to check for C4
sugar/ethanol addition to wine (International Organisation of Vine and Wine 2006). In addition, d13C from vine
leaves, whole grape, seed, pulp, skin and/or grape must
sugars has been investigated as an integrated marker of
vine water status or intrinsic water-use efficiency during
doi: 10.1111/j.1755-0238.2009.00089.x
© 2009 Australian Society of Viticulture and Oenology Inc.
berry growth (Gaudillere et al. 2002, de Souza et al. 2005,
Poni et al. 2009), or as an indicator of region of origin,
vintage (Day et al. 1995) and of Vitis vinifera variety
(Yunianta et al. 1995, Van Leeuwen et al. 2001).
The isotopic ratio 18O/16O of water in wine is used to
determine water addition (International Organisation of
Vine and Wine 2006). The uptake of water by the roots of
the vine and the subsequent transport of water to the
leaves are not associated with any significant isotope fractionation, and can therefore be neglected (White 1989,
Ziegler 1989). d18O is higher in grape water than in soil
water as isotopic enrichment takes place mainly in the
leaves and also in the grape skin because of evaporation
and or exchange with atmospheric vapour (Martin et al.
1988, Tardaguila et al. 1997, Roßmann et al. 1999). The
isotopic ratio of grape water is controlled by the isotopic
composition of available soil water, relative humidity,
interacting time and isotopic ratio of atmospheric vapour.
All these variables mean that isotopic ratio changes are
284
Irrigation, variety and grape d18O and d13C values
dependent on seasonal climatic conditions, and therefore
annual databases are required (Roßmann et al. 1999).
The 18O/16O isotopic ratio has also been studied as a
marker of vintage and geographical origin (Roßmann
et al. 1999, West et al. 2007). More recently, a model has
been published for estimating d18O from meteorological
data (Hermann and Voerkelius 2008). In warm, dry
regions, vine irrigation is a key factor both for vegetative
and fruitful growth, and for physiological and biochemical functioning. However, there have been fewer studies
dealing with the oxygen than with the carbon stable
isotope ratio of grape. Little is known about how the d18O
isotopic ratio is affected by irrigation and whether this can
compromise its use as an indicator of water addition, or if
this parameter could be used alone or along with d13C as
a variety marker.
This paper examines the effect of irrigation and grapevine variety on d18O and d13C values of grape must from
eight different varieties, four foreign and four indigenous
to Spain, all cultivated in the same vineyard in an attempt
to limit the variables between treatments to irrigation.
The assay was conducted over two successive vintages.
Materials and methods
Reagents
CO2 (99.995) used as reference gas, 0.3% CO2 molar in He
used as equilibrium gas and He used as inert carrier gas
were from Carburos Metálicos (Barcelona, Spain). Vienna
Standard Mean Ocean Water (VSMOW) from the International Atomic Energy Agency (Vienna, Austria) and
Ethanol BCR 656 from the Institute for Reference Materials and Measurements (Geel, Belgium) were used for
d18O and d13C calibration, respectively.
Plant material and sample preparation
The trial was conducted on 2007 and 2008 vintages in the
same vineyard, where various grapevine varieties were
grafted on to Fercal rootstock in a plot representative of
the La Mancha growing region. The soil is a petrocalcic
soil horizon situated 35 cm below the surface, consisting
of petric calcisol that has developed on the alluvial part of
the River Guadiana (Elena et al. 1997). The experimental
design consisted of 64 vineyard blocks: eight grapevine
varieties, two treatments each (irrigated/non-irrigated)
and four replicates each one containing 20 vines. Irrigation ground water from a well located in the same vineyard was applied with drip emitters (4 L/h), two per vine.
The vines, grown on trellises and arranged on rectangular
frames measuring 3 ¥ 1.2 m, were trained to a double
Cordon de Royat system, with three to four spurs of two
buds on each arm.
The study was carried out on four Spanish indigenous
grapevines: Airén, Macabeo (white grapes), Tempranillo
and Garnacha (red grapes), and four foreign: Chardonnay, Sauvignon Blanc (white grapes), Cabernet Sauvignon and Merlot (red grapes). In the case of the 2007
vintage, 61 grape samples were taken, 31 from irrigated
vines and 30 from non-irrigated vines. In the case of the
Australian Journal of Grape and Wine Research 16, 283–289, 2010
2008 vintage, 63 samples were taken, 32 from irrigated
vines and 31 from non-irrigated vines.
The sampling was carried out randomly at technological maturity by picking 10–12 berries from the top,
middle and bottom of the cluster. We tried to sample
berries from both exposed and shaded clusters by
picking berries from four to five clusters per vine. The
size of the sample was around 2 kg. Grape juice was
obtained by pressing grapes in a manual spindle press;
SO2 (500 mg/L) was added to the juice and stored at 4°C
until analysis.
18
O/16O ratio measurement
An on-line gas equilibration and headspace introduction
system model GasBench II (ThermoQuest, Bremen,
Germany) was used, equipped with a gas chromatography column (PoraPlot Q, 25 m, 0.25 mm; Varian, Palo
Alto, California, USA) operating at 70°C and adapted to
an autosampler CombiPAL (CTC-Analytics, Zwingen,
Switzerland). Must samples were transferred (500 mL) to
10 mL vials with silicone septa, placed in the GasBench II,
flushed with 0.3% CO2 in He for 10 min and then left for
24 h at 27°C before analysis. During this equilibration
time, an exchange reaction took place between oxygen in
CO2 and H2O (Eqn 1). CO2 was then isolated from the vial
headspace and introduced in the isotope ratio mass spectrometry (IRMS) system:
12
C16O2 + H 218O ↔ 12C16O18O + H 216O
(1)
The GasBench II was coupled to a Delta-Plus IRMS (ThermoQuest) equipped with three Faraday cup detectors to
simultaneously and continuously monitor the [CO2]+
signals for the three major ions at m/z 44 (12CO2), m/z 45
(13CO2 and 12C17O16O) and m/z 46 (12C18O16O). Oxygen
isotope composition was expressed as:
δ18Osample = [( Rs Rst ) − 1] × 1000
where Rs is the 18O/16O ratio in the sample, and Rst is the
ratio of the international standard used, VSMOW.
13
C/12C ratio measurement
Determination of the carbon isotope ratios of grape must
was carried out by on-line analysis using a ThermoQuest
Flash 1112 elemental analyser equipped with an
autosampler and coupled to a Delta-Plus IRMS (ThermoQuest) through a ConFlo III interface (ThermoQuest).
One microlitre of grape must was carefully placed in a tin
capsule, and sealed. All of the carbon from the sample
was oxidized to CO2 in the reactors of the elemental
analyser, passed through a GC column to separate CO2
from the other gas generated and then brought into the
mass spectrometer by a helium flow (International
Organisation of Vine and Wine 2006). Carbon isotope
composition was expressed as:
δ13Csample = [( Rs Rst ) − 1] × 1000
© 2009 Australian Society of Viticulture and Oenology Inc.
Irrigation, variety and grape d18O and d13C values
Gómez-Alonso and García-Romero
where Rs is the 13C/12C ratio in the sample, and Rst is the
ratio of the international standard used, Vienna-Pee Dee
Belemnite.
All samples were analysed at least in duplicate.
Statistical analysis
The data from the must samples were subjected to analysis of variance (ANOVA) and the Student–Newman–Keuls
test to identify any statistically significant differences
between varieties and irrigation treatment. All statistical
tests were performed using SPSS software, version 12.0
(Chicago, Illinois, USA).
Results
18
O/16O isotope ratio of grape must water
The La Mancha region, where the study was conducted,
has a continental climate, characterized by long, dry
summers. Table 1 shows the rainfall recorded in the
2006/2007 and 2008/2009 hydrological years (RY) was
477 and 352 mm, respectively. According to the drought
index (DI) established by Tonietto (1999), this vinegrowing area was considered as a moderate drought
region in the period 1961–1990 (DI = -86). However,
because of climate change, this area is currently included
in the severe drought group with DI = -135 and -127
(mm) in 2007 and 2008, respectively (meteorological
data for DI determination from Centro Regional de Estudios del Agua 2009). Because of this climate trend, irrigation is becoming increasingly necessary in this region,
as in other Mediterranean areas (Laget et al. 2008), for
adequate vine management. Table 1 also shows rainfall
registered in the vineyard during the irrigation period,
and the irrigation volume during the summers: 312, 272
and 72 L/grapevine in the 2007 summer, and 312, 272
and 56 L/grapevine in 2008 in July, August and September, respectively. No statistically significant differences
were found between mean d18O value of groundwater
used for irrigation (-7.9 ⫾ 0.1‰) and rainfall weighted
mean d18O value (-7.7 ⫾ 0.9‰) from the region where
the study was conducted (Global Network of Isotopes in
Precipitation 2009).
285
The last two columns of Table 1 show the mean value
and standard deviation for d18O when samples are grouped
by year and irrigation regime. Statistically significant differences (P ⱕ 0.001) between d18O grape water values of
watered and non-watered vines were found for both years;
this difference between treatments was higher in the 2008
vintage. When d18O values from the same watering treatment were compared for the two years, no differences
were found for irrigated vines, while d18O water from
non-irrigated vines differed by 2‰ (P ⱕ 0.001).
When samples were grouped by vine variety, the differences between water treatments observed previously
in the 18O/16O ratio persisted in both harvests (Table 2).
The 2007 crop of Tempranillo was the only case in which
the difference was not statistically significant, although
the trend was the same as in the other varieties, with a
higher d18O value for non-irrigated vines. The lowest
irrigation-dependent variation observed in d18O grape
water was 0.692‰ for Merlot in 2007, and the highest
was for Macabeo in the 2008 crop season. The mean
differences observed in d18O between the treatments were
1.065 in 2007, and 2.965 in 2008.
Table 2. d 18O (‰) values of grape must water classified
according to irrigation regime and variety for 2007 and
2008 harvests.
d 18O (‰) Harvest 2007
Grape Variety
Non-irrigated
Airén
Macabeo
Tempranillo
Garnacha
Sauvignon Blanc
Chardonnay
Merlot
Cabernet Sauvignon
Irrigated
Difference
n
Mean
SD
n
Mean
SD
4
4
3
4
4
4
4
4
10.7a
10.4a
10.5a
10.8a
11.6b
12.1b,c
12.2b,c
12.6c
0.2
0.3
1.0
0.3
0.6
0.9
0.5
0.6
4
4
3
4
4
3
4
4
9.5a
9.1a
9.8a
9.8a
10.7b
11.1b,c
11.5c
10.9b
0.3
0.2
0.2
0.6
0.2
0.1
0.2
0.6
1.1***
1.2***
0.7
1.0**
1.0**
1.0**
0.7**
1.7***
d 18O (‰) Harvest 2008
Grape Variety
18
Table 1. Mean irrigation volumes, rainfall and d O (‰)
of grape must water.
Harvest
2007
2007
2008
2008
Treatment
NI (n = 31)
I (n = 30)
NI (n = 31)
I (n = 32)
Irrigation
(L/vine)
RY
(mm)
RDIP
(mm)
0
656
0
640
477
477
352
352
37
37
22
22
d 18O (‰)
Mean
SD
11.4a*
10.3b
13.3a*
10.4b
1.0
0.9
1.5
1.7
NI, non-irrigated vines; I, irrigated vines; RY, rainfall in meteorological year;
RDIP rainfall during irrigation period (from 1st July to 20th September in 2007
and to 15th September in 2008). Different superscripts in the same column and
year denote statistically significant differences between irrigation treatments at
p ⱕ 0.001. * Denote statistically significant differences between data for different
year and the same irrigation treatment at p ⱕ 0.001.
© 2009 Australian Society of Viticulture and Oenology Inc.
Non-irrigated
Airén
Macabeo
Tempranillo
Garnacha
Sauvignon Blanc
Chardonnay
Merlot
Cabernet Sauvignon
Irrigated
Difference
n
Mean
SD
n
Mean
SD
4
4
3
4
4
4
4
4
10.7a
12.7b,c
13.5c,d
13.3c
14.3d,e
15.2e
14.7e
12.2b
0.6
0.1
0.6
0.6
0.6
0.4
0.1
1.1
4
4
4
4
4
4
4
4
8.8b
7.5a
11.2d
9.5c
11.6d,e
12.0e
12.4f
9.8c
0.1
0.2
0.3
0.4
0.3
0.1
0.2
0.6
2.0***
5.1***
2.3***
3.8***
2.7***
3.2***
2.3***
2.4***
Different superscripts in the same column and year denote statistically significant
differences between varieties (Student-Newman-Keuls, a = 0.01). ***, ** and
* denote statistically significant differences in the same line at p ⱕ 0.001, 0.01
and 0.05 respectively between irrigation treatments.
286
Irrigation, variety and grape d18O and d13C values
Australian Journal of Grape and Wine Research 16, 283–289, 2010
The effects of variety on d18O were determined by
one-way ANOVA, and the Student–Newman–Keuls post
hoc test results established three subsets in 2007: subset A,
which included the Airén, Macabeo, Tempranillo and Garnacha varieties, all considered indigenous Spanish grapes,
with the lowest 18O/16O ratios, while the foreign varieties
were classified in subsets B and C. The results for the
second year did not group varieties so clearly, but again the
indigenous varieties presented lower d18O values with the
only exception of Cabernet Sauvignon, which, in 2008,
showed d18O values lower than those for some Spanish
varieties. Table 3 shows that when varieties were grouped
into indigenous Spanish (Airén, Macabeo, Garnacha and
Tempranillo) and foreign (Sauvignon Blanc, Chardonnay,
Merlot and Cabernet Sauvignon), the 18O/16O ratio was
statistically significantly lower in the indigenous varieties
irrespective of the year or the irrigation regime. In order to
determine if differences on d18O between varieties were
caused by the date of sample collection or to a varietal
factor, Figure 1 shows the behaviour of the 18O/16O ratio
versus the date of sampling. Note that d18O was higher in
foreign varieties regardless of the sampling date in the
2007 harvest in both irrigated and non-irrigated grapevines. In 2008, d18O values tended to be lower in the
late-ripening varieties, possibly because of the cumulative
rainfall during this period, which was higher than in 2007;
however, in the foreign varieties, 18O/16O ratios were consistently higher for the same sampling dates.
Table 3. d18O (‰) values of grape must water classified according to irrigation regime and
geographical origin of varieties for 2007 and 2008 harvests.
Year/treatment
Spanish indigenous
2007 Non-irrigated
2007 Irrigated
2008 Non-irrigated
2008 Irrigated
Total
Foreign
Difference
n
Mean
SD
n
Mean
SD
15
15
15
16
61
10.6
9.5
12.4
9.2
10.4
0.5
0.5
1.2
1.4
1.6
16
15
16
16
63
12.1
11.0
14.1
11.5
12.2
0.7
0.5
1.3
1.1
1.5
1.6*
1.5*
1.7*
2.2*
1.8*
*Denote statistically significant differences in the same line at P ⱕ 0.001.
7
16
6
14
5
13
15
6
14
5
13
12
4
12
4
11
3
11
3
10
d18O (‰) VSMOW
7
16
2
9
8
1
(a)
0
7
10
8
16
15
15
14
14
13
13
12
12
11
11
10
10
9
1
(c)
0
7
16
8
2
9
Accumulated Rainfall (mm)
15
9
(b)
7
Aug 27
8
Sep 1
Sep 6
Sep 11
(d)
7
Aug 20
Aug 25
Aug 30
Sep 4
Sep 9
Sep 14
Sampling Date
Figure 1. A plot of the d18O of grape must water in the 2007 and 2008 harvests versus the date of sampling. Samples: 䊏, Airén; 䊉, Garnacha;
䉱, Macabeo; 夹, Tempranillo; 䊐, Cabernet Sauvignon; 䊊, Chardonnay; 䉭, Merlot; 夽, Sauvignon Blanc. (a) 2007 non-irrigated; (b) 2007
irrigated; (c) 2008 non-irrigated; (d) 2008 irrigated.
© 2009 Australian Society of Viticulture and Oenology Inc.
Irrigation, variety and grape d18O and d13C values
Gómez-Alonso and García-Romero
287
Table 4. Mean irrigation volumes, rainfall and d13C (‰) of grape must sugar.
Harvest
2008
2008
Treatment
d13C (‰)
Irrigation (L/vine)
Non-irrigated (n = 31)
Irrigated (n = 32)
0
640
Mean
SD
-21.0*
-22.5*
0.7
0.4
*Denote statistically significant differences between samples of different irrigation treatments at P ⱕ 0.001.
Table 5. d13C (‰) values of grape must sugar classified according to irrigation regime and variety
for 2008 harvest.
d13C (‰)
Grape variety
Difference
Non-irrigated
Airén
Macabeo
Tempranillo
Garnacha
Sauvignon blanc
Chardonnay
Merlot
Cabernet sauvignon
Irrigated
n
Mean
SD
n
Mean
SD
4
4
4
4
4
4
4
4
-20.5c,d
-20.7b,c,d
-21.2a,b,c
-20.9a,b,c,d
-21.6a
-21.4a,b
-21.4a,b
-20.1d
0.6
0.5
0.4
0.4
0.2
0.3
0.4
0.6
4
4
3
4
4
3
4
4
-22.1c
-22.5a,b,c
-22.6a,b
-22.5a,b,c
-22.8a
-22.9a
-22.6a,b
-22.3b,c
0.2
0.2
0.3
0.2
0.2
0.5
0.2
0.3
1.6*
1.8*
1.4*
1.6*
1.2*
1.5*
1.3*
2.1*
*Denote statistically significant differences in the same line at P ⱕ 0.001 between irrigation treatments. Different superscripts in the same
column denote statistically significant differences between varieties (Student–Newman–Keuls, a = 0.01).
13
C/12C isotope ratio of grape must sugar
Analysis of d13C of grape sugars during 2008 harvest confirmed the effect of water availability on this isotope ratio.
Irrigated grapes showed significantly (P ⱕ 0.001) lower
13
C/12C ratios than non-irrigated grapes (Table 4).
When grapevine variety was considered as a variable,
the effect of irrigation on d13C was observed in all cases,
with differences ranging from 1.196 for Sauvignon Blanc
to 2.117 for Cabernet Sauvignon (Table 5). This table also
shows that d13C was lower in the foreign than in the
indigenous varieties in both irrigated and non-irrigated
vines. As it was also observed for d18O in 2008, the only
exception to this general trend was Cabernet Sauvignon,
which showed higher d13C values than some Spanish
varieties under both irrigation treatments. When varieties
were grouped in this way irrespective of the watering
treatment, a 1.583‰ variation was found in the 13C/12C
ratio (P ⱕ 0.001).
Discussion
The 18O/16O isotopic ratios observed in this work were
much higher than those found in the relevant literature
for Italian, French and German wines of different vintages. d18O values have been found to range from -3.3‰
in some German wines to 7‰ in Italian wines, while
French wines present intermediate values (Roßmann
et al. 1999, Hermann and Voerkelius 2008). 18O/16O isotopic ratios for La Mancha grape juices are also higher
© 2009 Australian Society of Viticulture and Oenology Inc.
than those for Korean grape juices, which consistently
show negative d18O (Bong et al. 2008). This can be
explained because precipitation and groundwater show
higher d18O in southern Europe than in northern Europe
(Global Network of Isotopes in Precipitation 2009), and
also because the weather in La Mancha during grape
growing is warmer and dryer than in most of the areas of
Germany, France or Italy, which increases transpiration
through leaves and grape skin, and consequently 18O/16O
isotopic ratio of grape water (Roßmann et al. 1999).
The data presented in Table 1 show the effect of irrigation on d18O of grape juice. The fact that the isotopic
enrichment is lower for this isotopic ratio in irrigated
vines means that the ratio between the water absorbed by
roots and the water evaporated is higher. However, the
effect of irrigation on d18O (around 2‰ in the 2007 and
3‰ in the 2008 vintages) was comparable to or smaller
than the effect of varietal differences: up to 2.4 and 4.8‰
in 2007 and 2008 vintages, respectively. Roßmann et al.
(1999) asserted that the influence of the variety on d18O
values is an indirect one because those differences are
caused by the date of harvest, because of the strong
impact of climate during the ripening and harvesting of
grapes. Consequently, water in grape varieties that
mature early has higher d18O values than water in late
ripening varieties. As Figure 1 shows, the differences
between varieties are not due only to the date of harvest,
because grapes of different varieties sampled at the same
288
Irrigation, variety and grape d18O and d13C values
time and taken from the same vineyard showed different
18
O/16O isotopic ratios. It was observed that d18O values
were usually higher in foreign than in indigenous
Spanish varieties. This suggests some physiological differences that lead to a lower water isotopic discrimination in
the indigenous Spanish varieties studied than in nonindigenous varieties.
The statistically significant effect (P ⱕ 0.001) of
vintage on d18O observed for non-irrigated vines (Table 1)
can be explained by the rainfall registered in 2007 crop
season during the berry development period, mainly July
and August, which was much higher than in the 2008
vintage (19 and 1.2 mm, respectively). The effect of other
climatic factors apart from rainfall on 18O/16O isotopic
ratio seems to have been negligible in the vintages studied
because no differences were found between irrigated
vines, which received practically the same water input in
both years.
The d13C values found in this work are comparable to
those reported by Gaudillere et al. (2002), although the
range was smaller in our samples. 13C is 1.1% of atmospheric CO2, but in C3 plants ribulose-1,5-bisphosphate
carboxilase/oxygenase uses preferentially 12C for sugar
synthesis during photosynthesis (Farquhar et al. 1989).
When soil water availability decreases, leaf stomata close
partially and atmospheric CO2 interchange is reduced,
leading to a smaller isotopic discrimination. For that
reason, d13C values reflect water status during photosynthesis and grape ripening (Farquhar and Richards
1984), and make it possible to differentiate between irrigation regimes. d13C values close to -20‰ as found in
non-irrigated vines (Table 4) indicate considerable water
restriction (Gaudillere et al. 2002), while d13C values for
the irrigated ones are consistent with a lower water
restriction but far from those found by Gaudillere et al.
(2002) for less stressed vines.
The decrease in the 13C/12C isotope ratio (-1.583‰) of
grape must from irrigated vines with respect to nonirrigated vines was consistent with that reported in the
literature by similar studies. de Souza et al. (2005)
observed higher d13C values of solid parts of grape and leaf
in non-irrigated vines. These differences were significant
in the case of fully irrigated and non-irrigated vines, while
they found intermediate values for partial root zone
drying and deficit irrigation. That study reported differences of up to 3‰ in the 13C/12C isotope ratio of grape
pulp, and a good correlation between d13C and water
stress integral. A similar relationship between carbon isotopic ratio of sugars of grape must and pre-dawn leaf
water potential was found by Gaudillere et al. (2002).
However, more recent studies have reported no differences in d13C determined by irrigation treatments (Poni
et al. 2009).
Several researchers who have investigated the genetic
variability of carbon isotope composition have concluded
that it could serve as an indicator of stomata control in V.
vinifera species, and hence as an indicator of resistance to
water stress (Gaudillere et al. 2002). Different varieties
subjected to the same irrigation treatment showed differences of up to 1.49 and 0.826‰ in d13C for non-irrigated
Australian Journal of Grape and Wine Research 16, 283–289, 2010
and irrigated vines, respectively; these differences are
smaller than those reported in the literature: up to 2.6‰
(Gaudillere et al. 2002). In Table 5, we can see how, as
expected, these differences in carbon isotope composition
are greater in non-irrigated than irrigated vines, because
it is in such stressful conditions that stomata control is
most important.
These observations regarding the effect of variety on
d13C corroborate the observations for d18O and previous
studies found in literature. Grape water isotopic enrichment with respect to ground water is mainly caused by
isotope fractionation at leaf sites produced by evapotranspiration (Bong et al. 2008, Hermann and Voerkelius
2008) controlled mainly by stomata closure (Loveys et al.
2000). Then, part of the isotopically modified water is
transported into the grapes where its isotopic signature is
assumed to be more or less preserved and a time average
of individual isotopic ratios of different climatology
during grape growing (Hermann and Voerkelius 2008). In
general, d18O values were higher in the foreign than in
the indigenous Spanish varieties, and hence there was
more transpiration; this corresponds to lower d13C values,
indicating less stomata control/closure under water stress
conditions. The only exception to this pattern was Cabernet Sauvignon, which in 2008 showed similar isotopic
ratios to those for Spanish varieties in both elements. In
fact, a statistically significant correlation (P ⱕ 0.05) was
observed between d13C and d18O values for both nonirrigatied (r2 = 0.702) and irrigated (r2 = 0.443) vines.
Conclusions
Irrigation had a statistically significant effect in both d18O
of grape water and d13C of berry sugar. This research,
using grape samples from the same vineyard, shows that
the variations in d18O of grape water and d13C of berry
sugar caused by the effect of V. vinifera varieties were not
because only of differences in the vegetative cycle of each
variety. It further suggests that water suffers a lower isotopic discrimination in the indigenous Spanish varieties
studied than in non-indigenous varieties.
Acknowledgements
Dr Sergio Gómez Alonso wishes to thank the European
Social Fund and the INIA for co-funding his contract at
the IVICAM.
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Manuscript received: 24 March 2009
Revised manuscript received: 22 July 2009
Accepted: 27 August 2009