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Am. J. Enol. Vitic. 61:3 (2010)
The 3-alkyl-2-methoxypyr azines (M Ps) are a class of
odorant s associated wit h “g reen,” herbac eous aroma s of
some Bo rd ea ux w inegr ap e (Viti s vin ifer a L.) culti va rs.
Qu antitatively, 3-isobut yl-2-methoxypyr azine (IBMP) is
the predominant MP in grapes and wine, typically an order
of magnitude h igher i n concentration t han 3-isopropyl-2-
methox ypyr az ine (I PMP) and 3-sec -butyl-2-met hoxypyr-
azine (sBM P) (Alberts et al. 2009). The sensory detection
threshold for IBMP is re por ted to range from 0.5 to 2 pg/g
in water ( Butter y et al. 1969, Kotseridis et al. 1998, Seifert
et al. 1970) and 10 to 15 pg/g in red wine (de Boubee et al.
1Graduate Student, Cornell University, Field of Horticulture, Plant Sciences
Building, Ithaca, NY 14853; 2Assistant Professor of Enology, 3Former Postdoc-
toral Scient ist, Cornell University, Depar tment of Food Science and Technol-
ogy, 630 W. North Street, Geneva, NY 14456; 4Former Postdoctoral Scientist,
Cornell University, Depart ment of Horticultural Sciences, Geneva, NY 14456;
5Research Technician, 6Viticultu rist, Cornell Cooperat ive Extension Suffolk
County, Long Island Horticultural Research and Extension Center, 3059 Sound
Avenue, Riverhead, NY 11901; 7Research Suppor t Specialist, Depa rtment of
Horticultural Sciences, Geneva, N Y 14456; and 8Assistant Professor of Viti-
culture, Cornell University, Depar tment of Hor ticultural Sciences, Geneva,
NY 14456, and Department of Hor ticulture, Ithaca, NY 14853.
*Corresponding aut hor (email: jjs365@cornell.edu)
Acknowledgments: The authors thank Sheldrake Point Vineyard and Pellegrini
Vineyard s for cooperation on this project, Imeld a Ryona for assistance with
sample preparation, and Terry Bates for assistance in editing this manuscript.
Manuscript submitted Nov 2009, revised Mar 2010, accepted Apr 2010
Copyright © 2010 by the American Society for Enology and Viticulture. All
rights reserved.
Impact of Severity and Timing of Basal Leaf Removal
on 3-Isobutyl-2-Methoxypyrazine Concentrations
in Red Winegrapes
Justin J. Scheiner,1* Gavin L. Sacks,2 Bruce Pan,3 Said Ennahli,4
Libby Tarlton,5 Alice Wise,6 Steven D. Lerch,7 and Justine E. Vanden Heuvel8
Abstract: Field st udies were condu cted on Vitis vinifera L. cvs. Cabernet fr anc and Merlot t o evaluate the ef-
fects of basal leaf removal timing and severity on 3-isobutyl-2-methoxypyrazi ne (IBMP) concent ration in g rape
ber ries. Treatments consisted of removing either 50% or 100% of leaves from t he f ru iting zone at eit her 10 days
after anthesis, 40 days after anthesis , or 60 d ays after anthesis. In the second year of the Cabe rnet franc st udy, a
15-day postveraison leaf removal treatme nt was also included. In both years of the Cabernet franc study, signifi-
cant reductions i n I BMP (range = 28 to 53%) were observed b efore veraison compared with the control in both
10 days aft er anthesis treat ments (50% and 100% leaf removal). In 2007, all leaf removal treatments significantly
reduced IBMP concentrations compared with the control (46 to 88%) i n Cabernet franc berr ies at har vest, w ith
the greatest reduction observed in the 100% leaf removal tre atments at 10 days aft er anthesis and 40 days after
ant hesis. In 2008, the 100% leaf removal t reatment at 10 days after anthesis and the 50 and 100% leaf removal
treatment s at 40 days after anthesis sig nificantly reduce d IBMP concentrations (34 t o 60%) in matur e Caber net
franc berries. In the Me rlot tr ial, all leaf removal treatments signif icantly reduced I BMP concentrations (38 to
52%) at ha rve st. In summary, early season (10 to 40 day af ter anthesis) basal leaf removal reduced I BMP accu-
mulation preveraison compared w ith the cont rol in both studies, suggesting that early leaf re moval is a mor e ef-
fective management strategy to reduce IBMP accu mulation i n grape berries than leaf removal later in the season.
Key words: IBMP, accumulation , cluster exposure, methoxypyra zine
2000, Kotseridis et al. 1998). When present at concentra-
tions near sensory threshold, MPs may contribute positively
to wine quality by adding complexity and , in some cases,
var ietal cha racter (Allen et al. 1991). At higher concent ra-
tions, MPs can result in excessive herbaceousness and sup-
pressed fruitiness in wines (Allen and Lacey 1999, Hein et
al. 2009, Pickering et al. 2005). MPs are efficiently ext ract-
ed by conventional red wine practices, and their concentra-
tions in wine are strongly correlated to their concentrations
in grapes (Ryona et al. 2009). Several studies have evalu-
ated the ef ficacy of vin if ication and cellar ing practices in
reducing MPs (Blake et al. 2009, de Boubee 2003, Marais
1998, Picker ing et al. 2006) and have generally concluded
th at remediation of M Ps is ineffec tive or else re su lt s i n
other nonselective changes to the wine. Vit icultural man-
age ment st rategies th at reduce MPs i n the vineyard have
thus been proposed to be the most effective way to control
MP concentration in wine (Boga rt and Bisson 2006).
In grape b er r ies, IBMP beg ins to a ccumulat e a roun d
10 d ays aft er anthesis with a pea k i n con ce nt ration oc-
cu rring approximately 0 to 14 days before veraiso n, fol-
lowed by a rapid decline during maturation (de Boubee et
al. 20 00, Hashizume and Samuta 1999, Ryona et al. 2008,
Sala et al. 20 04). IBMP concent rations in mature berries
are reported to be less than 10% of their preveraison peak
concent rations. A strong correlation (R2 = 0.936) between
IBMP concentrations in mature Cabernet franc berries and
preveraison peak concent rations has been reported ( Ryona
Am. J. Enol. Vitic. 61:3 (2010)
et al. 2008), suggesting that final IBMP concentrat ion is
primarily deter mined preveraison. Thus, management prac-
tices that affect initial accumulation of MPs in g rapes pre-
verai son ar e ex pected t o more d ramatically impact f in al
MP concentrations at har vest than inter ventions later in the
season, assuming similar maturities.
Fruit-zone leaf removal is a com mon viticultural prac-
tice and has be en de mo ns trated to y ield improved fru it
chem ist ry at harvest ( Percival et al. 1994, Poni et al. 2006,
Rey nolds et al. 1996, Zoecklei n et al. 1992, 1998) and to
improve fungal control (Chellemi and Marois 1992, Percival
et al. 1994, Wolf et al. 1986, Zoecklein et al. 1992). T hese
effects are generally hypothesized to be mediated through
an increase of sunlight reaching the f ruiting zone. Several
gr oups h ave observed t hat cluster light exposu re results
in lowe r MP concentration s in mature fru it (Allen et al.
1996, de Boubee et al. 2002, de Boubee 2003, Marais et al.
1999, Noble et al. 1995, Ryona et al. 2008). Rece nt work
suggests that sun- exposed clusters accumulate less IBMP
pr ever aison tha n sha de d cluste rs w it hin the same v ine
(Ryona et al. 2008) and that the propor tional differences
pe rsist until harvest, alt houg h the physiolog ical mecha -
nisms behind these effects are not understood. Most of the
aforementioned studies have observed differences between
shaded and exposed f ruit by using artificial shading or tak-
ing advantage of natural variation in light exposure within
the canopy, but little work has been published on the effec-
tiveness of specif ic vineyard practices (e.g., leaf removal)
to reduce M P a ccumulation preveraison and subs equent
levels at harvest. A 68% reduction in IBMP concentration
of Cabernet Sauvignon at harvest resulted from removal of
lateral shoots and basal leaves on the east side of the f ruit-
ing zone at fruit set compared to an unthinned control (de
Boubee 2003). A similar t reatment imposed postver aison
resulted in only a 10% reduction in IBMP at harvest. How-
ever, that repor t did not consider more than one preveraison
leaf removal timi ng, the period when the accumulation of
MPs is greatest (Ryona et al. 2008), nor did it i nvestigate
the effects of the severity of leaf removal. We are unaware
of a ny other literatu re that has quantif ied the i mpac t of
leaf removal on M Ps in grape berries. The objective of this
study was to investigate the impact of timing and severity
of leaf removal on IBMP concentration in Cabernet franc
in the Finger Lakes and Merlot on Long Island, New York.
Materials and Methods
Experimental design. Two commercial v ineyards lo-
cated in Ovid, New York (42.67°N, 76.82°W; Fi nger Lakes
AVA, Cay uga Lake) and Cutchogue, New York (40.99°N,
72.48°W; Long Island AVA, North Fork) were used in this
st udy. The soil ty pe s we re classified by t he U.S. D.A. as
Howard ser ies with a g ravelly loam structure, well drained,
an d a de pt h of >2 m a nd as Have n ser ie s with a loa my
st r uct ure, well d rai ne d, a nd a de pt h of >2 m at Fi ng er
Lakes and Long Island, respectively. Vines at the Finger
Lakes site were Vitis vinifera L. cv. Cab er net franc cl. 1
grafted on 3309C rootstock trained to a Scott Henry system
with four canes. The upper canes were at 1.3 m height and
shoots vertically positioned. The lower canes were at 1.0 m
height and shoots downward positioned. Vines at the Long
Isla nd site were Merlot cl. 181 grafted on 3309C rootstock
trained to a combination of low wire cordon and a f lat cane
system with either two cordons or two canes at 1.0 m height
and shoots vertically positioned. Vine spacing for both sites
was 2.0 m between vi nes and 2.5 m betwee n rows. Vine
management was performed according to the standard viti-
cult ural practices for vinifera in the Finger Lakes and Long
Island regions. The experimental design was a randomized
complete block with fou r re plications. The expe rime nt al
plot at each site consisted of fou r rows, and each exper i-
mental unit consisted of eight contiguous vines in each row.
Treatments consisted of a control (no leaf removal); re-
moving the first, third, and f ifth leaf from the base of each
shoot at 10 days af ter anthesis (10 DA A 50%), 4 0 d ay s
after ant hesis (40 DAA 50%), or 60 days after a nthesis (60
DAA 50%); and removing the first five leaves beginning
at the base of each shoot at 10 days after anthesis (10 DAA
100%), 40 d ays after anthesis (40 DAA 100%), or 60 days
after a nthesis (60 DAA 100%). Two additional treatments
were added at the Cabernet franc site in the second year of
the st udy: removi ng the first, thi rd, and f if th leaf from the
base of each shoot at 15 d ays after veraison (15 DAV 50%)
or removi ng the f i rs t five leaves from the base of e ach
shoot at 15 days after veraison (15 DAV 100%). All basal
leaf removal treatments were applied by hand on all f ruit-
ing and nonfruiting shoots of each vi ne. The beginning of
bloom was noted on 18 June 2007 and 19 June 2008 (Cab-
er net f ra nc), and 22 Ju ne 20 08 (Merlot). Time of anthesis
was determined as the date on which 50% capfall wa s vi-
sually estimated. In 2007, the calendar dates for the treat-
ments in Caber net franc were ant hesis (17 June), 40 d ays
after anthesis (27 July), 60 days after anthesis (16 Aug), and
harvest (21 Oct). In 2008, the calend ar dates for the treat-
ments i n Cabernet franc and Merlot were anthesis (18 June
and 21 Ju ne, respectively), 40 days after anthesis (28 July
and 31 July), 60 days after anthesis (17 Aug and 20 Aug),
and harvest (20 Oct and 16 Oct). The 15-day post veraison
treatment was performed on Cabernet franc on 6 Sept 2008.
Sampling and har vest. Five days after each basal leaf
remov al tr eatment was i mpos ed in 2007 (15, 45, and 65
days after a nthesis) a nd 5 to 15 d ays after ea ch basal leaf
re moval treat me nt wa s i mposed in 2008 (15, 50, 75, 85
days after a nthesis) in Cabernet f ranc, 50 -ber ry samples
were collected at random f rom each experiment al unit for
IBMP quantif ication. At har vest, 150 berries were collected
at random from each exper imental unit in Cabernet f ranc
and Merlot for IBMP qua ntification and chemical analysis.
The berr y samples were placed in plastic storage bags and
immed iat ely frozen followed by storage at -23°C for later
analysis.
Yield components wer e ass es sed in the 20 08 Ca ber-
net f ranc and Merlot studies. At har vest, yield (measured
with a hanging scale accurate to 0.01 kg; model SA3N340,
Salter Brecknell, Fairmont, MN) and cluster counts we re
Am. J. Enol. Vitic. 61:3 (2010)
deter mined for each vine and an average was recorded for
each replication. Crop weight and number of clusters were
used to calculate average cluster weight. Yield data was not
recorded in the 2007 Cabernet franc st udy as there was a
significant “green har vest” of fruit by the grower several
wee ks before harvest . In the 20 08 Cab er ne t franc study,
cluster thinning at veraison was performed by the grower in
all treatments to eliminate the least mature clusters.
Berry analysi s for Br ix , titrat able acid it y, and pH.
A subsample of 100 mat ure berries per experimental u nit
was removed f rom the -23°C freezer, placed in a 250-mL
beaker, and heated to 65°C for one hour in a water bath to
redissolve tartrates, pressed through cheesecloth with a pes-
tle, and the juice was collected for analyses. Soluble solids
(Br ix) were measured using a digital refractometer (model
300017; SPER Scientific, Scottsdale, AZ) with temperature
cor rection. Tit ratable acidity (TA) and pH were measured
with a n automat ic tit rate r (Titri no model 798, Metr ohm,
Riverview, FL), and TA wa s mea sured w ith a 5.0-m L ali-
quot of juice by tit ration against 0.1 N NaOH to pH 8.2.
Berry analysi s for IBMP. 3-Isobutyl-2-methoxypyr-
azine analysis was conducted using 50-berry samples. The
extraction method was head-space solid-phase microext rac-
tion (HS–SPME) and quantif ication was performed by com-
prehensive two-dimensional gas chromatography time-of-
flight mass spectromet ry (GCxGC–TOF–MS) as descr ibed
elsewhere (Ryona et al. 2009). In brief, HS–SPME was con-
ducted using a LEAP CombiPAL Autosample r (Carrboro,
NC) fitted with a th ree-phase fiber ( DVB/CA R/PDMS). A
10-min online incubation at 650 r pm agitation rate and an
incubation temperature of 80°C wa s applied before head-
space-fiber insertion and equ ilibrium. Following f iber in-
se rtion , the vi al wa s agit at ed at 100 r pm for 30 mi n at
80°C. Quantif ication was performed by GCxGC–TOF–MS
(Pegasus I V, Leco Cor p, St. Joseph, MI). SPME inject ions
were splitless with a desor ption temperature of 270°C. The
first capi llar y column (30 m × 0.25 mm × 0.50 μm) was
an RTX5 (Restek, Bellefonte, PA), and the second colu mn
(2.5 m × 0.10 mm × 0.10 μ m) was a VF-WAXms (Varian,
Palo Alto, CA). Helium was used as a car rier gas at a f low
rate of 1 m L/min. The temperatu re program was as fol-
lows: initial hold for 5 min at 40°C, followed by a 5°C/min
ramp to 120°C; then 2°C/min to 150°C, no hold; then 10°C/
min to 250°C, 15 mi n hold. The G CxGC modulation t ime
was 3 sec. The MS transfer line temperature was 230°C.
The TOF–MS was operated in EI mode with an ioni zation
energy of 70 eV. T he electron multiplier was set to 1680 V.
The TOF–MS data were st ored at an effective acquisition
rate of 12 0 Hz over a mass ra nge of m/z 20 to 40 0. The
qualifier ions were m/z = 124, 151, 166 for IBMP a nd m/z
= 126, 153, 168 for [2H2]-IBMP. The quantif ier ions were
m/z = 124 and 126, respectively.
Statistical analysis. Statistical analyses were conducted
with SAS statis tical sof tware (SAS Instit ut e, C ar y, NC ).
Data was subjected to the Proc GLM procedure and means
were separated using the Fisher’s protected least significant
difference (LSD) at the 5% sign if ica nce level. I BMP data
for harvested Cabernet franc berries in 2007 and 2008 were
not c ombined over yea rs due to significant yea r by t reat-
ment interaction.
Results
Leaf removal in Cabernet franc. Leaf removal timing
and severity impacted the concent rat ion of IBMP preverai-
son and at ha rvest in both 2007 and 2008. In 20 07, at 15
days after anthesis, IBMP was present at quantif iable con-
centrations (data not shown), but no significant difference
was observed in IBMP between the 10 DAA leaf removal
treatment and the untreated vines. At 45 days after anthe-
sis, both the 10 DAA 50% and 10 DA A 100% treatments
significantly reduced IBMP concentrations by 52 and 53%,
respect ively, compared to the control (Fig ure 1A). At 65
days after anthesis, t he concentration s of IBMP in the 10
DAA 50% and 10 DAA 100% treatments were 55 and 65%,
respectively, lower than the control (Figure 1B). The period
bet ween veraison (65 days af ter anthesis) and harvest (125
days after ant hesis) was marked by a decline in IBMP con-
cent rat ion. The IBMP concentration in mature fruit ranged
from 0.5 to 4.3 pg/g (Fig ure 1C) and averaged 1.1% of the
observed max im a (65 days aft er anthesis). Although the
only significa nt reduc tion in IBM P concentratio n at the
th ree preha rvest sample timings was observed for the 10
DAA 50%, 10 DAA 100%, and 40 DAA 100% treat ments,
all leaf removal t reatments significantly reduced IBM P in
mature berries with respect to the control (Figu re 1C). The
range in Bri x of t he C aber net fr an c be rries at harvest in
2007 was 19.4 to 22.3 (Table 1). The 10 DAA 50% and 10
DAA 100% t reatments signif icantly increased Bri x com-
pared to the control by 5 and 10%, respectively. TA ranged
from 6.4 to 8.6 g/L across treat me nts. Al l leaf removal
treatments except the 60 DAA 50% treatment significantly
reduced TA compared to the control.
In 2008, the 10 DAA 50% and 10 DAA 100% treatments
signif icantly reduced the concent ration of IBMP i n Caber-
net franc ber ries at 50 days after anthesis by 28% and 36%
(Figure 1D). At 75 days after anthesis the 10 DAA 100%
and 40 DAA 100% t reatments reduced I BMP concent ra-
tions by 25% and 48%, respectively (Figure 1E). At 85 days
after anthesis, there were no significant differences among
treatments (data not shown). At harvest (124 days after an-
thesis), the range in IBMP concent ration acros s all treat-
ments was 1.2 to 3.5 pg/g (Figu re 1F) and averaged 1.3% of
the obser ved preveraison (50 days after anthesis) maxima.
Although the 10 DAA 50% and 100% treat ments signif i-
ca nt ly reduced I BM P concent ra tion s at the preve raison
sample timing, t he 10 DA A 100%, 4 0 DAA 50%, and 40
DAA 100% leaf removal t reatments significantly reduced
IBM P concentrations (ra nge = 34 to 60%) at har vest. The
range in Brix was 21.1 to 22.5, with no significant differ-
ences among treatments (Table 1). TA ranged f rom 5.5 to
6.8 g/L among treatments. All treatments except 10 DAA
50% significantly reduced TA below the control. No dif-
ferences in juice pH were observed among the leaf removal
treatments. Yield, number of clusters, and average cluster
Am. J. Enol. Vitic. 61:3 (2010)
weight per vine in 2008 ranged from 3.4 to 4.1 kg, 21.6 to
26.1, a nd 145.7 to 181.8 g, respectively, with no significant
differences among t reatments (data not shown).
Leaf removal in Merlo t. At harves t (117 days after
ant hesis), the range in I BMP concentration i n Merlot ber-
ries across treatments was 3.2 to 6.7 pg/g (Figure 2). Leaf
removal at all timings and severities significantly reduced
IBMP by a r ange of 37 t o 52% compa re d to the cont rol.
Leaf removal timing and severity had no signif icant impact
on Brix, TA, and pH (Table 1). T he 10 DAA 50% t re at-
ment had sign if icantly lower yield (1.9 k g/vi ne) t han the
control and other t reatments (ra nge = 2.1 to 2.4 kg /vine).
No signif icant differences were observed among treatments
for nu mbe r of clusters pe r vine (12.8 to 14.8) and average
cluster weight (143.2 to 172.9 g).
Discussion
The highest concentrations of I BMP in Cabernet franc
were observed at the preveraison sample tim ings (65 days
after anthesis sa mpling in 2007, and at the 50 days aft er
anthesi s sampli ng i n 2008 (Figure 1). Differ ences in re -
por ted peaks between yea rs are likely a function of differ-
ent sample timings. In ag reement with our results, previous
research has demonstrated that IBMP reaches a maximum
in the 2 to 3 weeks before veraison (de Boubee et al. 2000,
Lacey et al. 1991, Ryona et al. 2008).
In both 2007 a nd 20 08, signif icantly lower IBM P con-
ce nt rations were observed in Caber net fr anc berries in
the 10 DAA 50% a nd 10 DAA 100% treatments compared
to the control at t he time poi nts ju st before or just aft er
veraison (65 days p osta nt he sis in 20 07, 50 days postan -
thesis in 20 08). No significant effe ct of leaf r emoval was
observed at these poi nts with the 40 DAA 50% or the two
60 DA A t reatments in either yea r, although the 40 DAA
100% treat ment had lower IBMP than the control in 2007.
These results are in concordance with a recent observation
that clu ster light exposu re preveraison reduces IBMP a c-
cumulation (Ryona et al. 2008). Because basal leaf removal
is widely shown to improve light penetration to the fruit-
in g z one ( Reyn olds et al. 1996, 20 06, Wolf et al. 1986,
Zoecklein et al. 1992), the reductions in IBMP concentra-
tion that we obse rved are likely due to incre ased cluste r
light exposure. Generally, we did not obser ve a significant
decrease in IBM P at the time point i mmediately following
the treatment application. We did not observe signif icantly
lower IBMP in the 40 DAA 50% treat ment at 45 d ays after
anthesis in 2007 or at 50 days after anthesis in 2008 nor did
we observe a significant effect for the 40 DAA 100% treat-
ment at 50 days after anthesis i n 20 08. We d id, however,
observe sign if icantly lower IBMP in the 40 DAA 100%
treatment at 75 days after anthesis in 2008, and at 65 days
after anthesis in 2007. Similarly, no significant difference
Figure 1 A
BCDEF
p
Am. J. Enol. Vitic. 61:3 (2010)
in IBMP was ob se rved between the 10 DAA treatments
and t he control at 15 days after anthesis in both years nor
was a difference observed at 75 days after anthesis between
the 60 DAA treatment s and the control. Thus, exce pt for
one case (40 DA A 100% in 2007), the impact of t he leaf
removal treat ment was not obser vable until >15 days after
the treatment was imposed.
Across all three stud ies, the largest and most consistent
dec reases for IBMP at har vest were observed in t he ea rly
leaf removal treatments. In the 2007 Cabernet franc study,
all t reatments had signif icantly lower IBMP than the con-
trol at harvest, with the g reatest reduction i n the 10 DAA
100% and 40 DAA 100% t reat ment s ( Fig ure 1C). I n the
2008 Cab er net f ranc st udy, the 10 DAA 100%, 4 0 DA A
50%, and 40 DAA 100% treatments contained significantly
lower IBMP at harvest compared to the control (Figure 1F).
In the 2008 Merlot study, all t reatments resulted in lower
IBMP than the control at har vest (Figure 2). These results
support t he previous hy pothesis t hat cluster light exposu re
pr ever ai so n inhibits ac cumulat ion p re vera ison, but has
lit tle effect postveraison, and that the relative differences
in I BMP established before f ruit mat urat ion per sist unti l
harvest (Ryona et al. 2008).
Althoug h preveraison leaf removal (10 or 40 days post-
anthesis) resulted in the largest decrease in I BMP levels
at har vest compared to the control i n the Cabernet f ranc
studies, we also observed a smaller but still sign ificant de-
crease in IBMP for the 60 DAA treatments in both the 2007
Cabernet franc and 2008 Merlot stud ies. Previou s wo rk
(Allen et al. 1996, Marais et al. 1999, Ryona et a l. 2008)
indicates t hat clu ster exposure reduc es IBM P accu mula-
tion preveraison, but does not increa se IBMP degradation
postveraison on a percentage basis. A p otent ial explana-
tion is that IBMP sy nthesis and degrad ation are occurring
simultaneously, at similar rates, in ber ries 40 to 60 days
Figure 3
Table 1
Treatment Brix TA (g/L) pH
2007 Cabernet franc
2008 Cabernet franc
2008 Merlot
p
Figure 2
p
Am. J. Enol. Vitic. 61:3 (2010)
postanthesis. Thus, IBMP synt hesis may still be occu rring
around ver aison although the berry IBMP concent rat ion is
unchanged. In s uppor t of this hypothesis, we observe d a
sizeable decrease (41%) in 2008 Cabernet franc for the 40
DAA 100% treatment at Day 75 compared to the control,
even though no significant decrease was observed at Day
50. However, IBMP synthesis li kely does not persist late
into the season. In the 15-day postveraison treatments (50%
and 100%) in the 2008 Caber net f ranc study, we observed
no signif icant change in IBMP levels at harvest compared
to the control (Figu re 1F). Sim ilarly, post veraison clust er
sha ding has been repor ted to have no impact on I BMP in
Cabernet Sauvignon (Sala et al. 2004).
Several st udies have reported that g rowing season tem-
peratu re a nd MP cont ent in mat ure ber ries are inversely
correlated (Allen et al. 1991, 1994, Falcao et al. 2007). The
total growing deg ree d ays (GDD, base 10°C) accumulated
at t he Finger La kes site i n 2007 and 20 08 from 1 Jan to
harvest (17 and 16 Oct) w as 1552 and 1410, r es pect ively
(Figure 3). Although there were 142 more tot al GDD accu-
mulated in 2007, there was less than 1% difference between
years in GDD accumulated f rom 10 days af ter anthesis to
veraison. The p er io d bet ween ver aiso n a nd harvest was
much warmer in 2007 (492 GDD during ripen ing) than in
2008 (349 GDD). Thus far, the relative importance of pre-
veraison versus postveraison growing season temperat ure
in deter mining IBMP cont ent in grapes has not been re -
ported. Althoug h we obser ved large diffe rences in GDD
between years, the average IBMP concentrations measured
at har vest in Cabernet franc (2.0 pg/g in 2007 and 2.3 pg/g
in 20 08) we re si milar, suggesti ng that the postveraison
GDD a ccumu la tion d id not have a strong inf luence on
final IBMP concentr ation. A st rong correlation has been
noted between IBMP concent rations at veraison and harvest
(Ryona et al. 2008), suggesting that final concentration is
dependent upon preveraison conditions.
Althoug h the harvest concentrations of IBMP observed
in this study are below repor ted sensory thresholds in red
wi ne (de Boubee et al. 20 00, Kotseridis et al. 1998), the
leaf removal t reatments in 2007 and 2008 reduced the final
IBMP concent ration in Cabernet franc by up to 88% and
60%, re spect ively, and in Merlot by up to 52% compared
to the control. In Caber net franc, IBMP accumulation was
reduced by up to 65% (2007) and up to 36% (2008) by the
10 DAA 50% and 10 DAA 100% treatments at the observed
maximum IBMP concentrations. Although we did not mea-
sure cluster light exposure for the various treatments in this
st udy, ou r f indi ngs may be consistent with oth er group s
that have evaluated t he effects of preveraison cluster light
exposu re on IBMP concent ration (Allen et al. 1996, de
Boubee 2003, Marais et al. 1999, Ryona et al. 2008).
Conclusion
Preveraison basal leaf removal treatments reduced IBMP
concent rat ion in Cabernet franc and Merlot berr ies at har-
vest. In Cabernet franc, accumulation of IBMP in the pre-
verai son pe riod was red uced by leaf removal, likely due
to improved lig ht intercept ion by the clusters. In a situa-
tion where IBMP is present in concentrations near sensory
threshold, leaf removal during the growing season could be
critical in reducing accumulation of I BMP. The earliest (10
days after anthesis and 40 days after anthesis) leaf removal
treatments yielded the greatest benef it in reducing IBMP.
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