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Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
doi:10.1016/j.envexpbot.2008.01.003
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Environmental and Experimental Botany xxx (2008) xxx–xxx
Chilling and heat requirements of sweet cherry cultivars and the relationship
between altitude and the probability of satisfying the chill requirements
Nuria Alburquerque a,∗, Federico Garc´
ıa-Montiel b, Antonio Carrillo c, Lorenzo Burgos a
aDpto. Mejora de Frutales, CEBAS-CSIC, Murcia, Spain
bCARM, Oficina Comarcal Agraria “Vega Alta”, Cieza-Murcia, Spain
cDpto. Cultivos Le˜nosos, Grupo de Fruticultura, IMIDA, La Alberca, Murcia, Spain
Received 13 August 2007; received in revised form 27 November 2007; accepted 16 January 2008
Abstract
Sweet cherry cultivars have different chilling and heat requirements for breaking rest and flowering. The knowledge of these requirements may
be valuable in the selection of the appropriate cultivars for producers and to avoid losses caused by an inadequate cultivar selection in a particular
area. Determination of chilling and heat requirements is also important within a breeding programme, when choosing parents to obtain early
flowering cultivars. Chilling requirements of seven cherry cultivars growing in south-eastern Spain were calculated using different methods (hours
below 7 ◦C, Utah and Dynamic model), which were compared. Recording hourly average temperatures at several locations during 2 years, the Utah
and Dynamic models performed better than hours below 7 ◦C. Different chilling requirements and slight differences in heat requirements were
observed in the studied cultivars. ‘Cristobalina’ and ‘Brooks’, the earlier-flowering cultivars, were those with the lowest chilling requirements.
‘Burlat’, ‘New Star’ and ‘Somerset’ had medium chilling and heat requirements for flowering, and ‘Marvin’ showed the highest values and also
the latest blooming date. All the studied cultivars may have their chilling requirements satisfied in the region of Murcia, if grown at least 650 m
above sea level. Some cultivars, such as ‘Cristobalina’ and ‘Brooks’, could successfully break dormancy already when grown at an altitude above
325 m.
© 2008 Elsevier B.V. All rights reserved.
Keywords: Dormancy; Dynamic model; Flowering; GDH; Hours below 7◦C model; Prunus avium L.; Utah model
1. Introduction
A specific knowledge of the influence of climatic conditions
on the phenology of cultivated temperate fruits allows farmers
to obtain an adequate productivity. Deciduous fruit trees and
other woody perennials of temperate climates require a certain
amount of winter chilling to overcome their dormancy. Once the
chilling requirements have been satisfied, heat is also required to
reach full bloom. The lack of chilling reduces vegetative growth
and yield (Erez and Couvillon, 1987; Erez, 2000). Temperate
fruits are grown in many different environmental conditions
and studies concerning chilling and heat requirements of dif-
ferent cultivars are valuable tools to avoid incomplete breaking
of dormancy or abnormal flowering.
Various models have been developed to measure the accu-
mulation of winter chilling in deciduous fruit-growing areas:
∗Corresponding author.
E-mail address: nalbur@cebas.csic.es (N. Alburquerque).
the Utah method (Richardson et al., 1974); low-requirements
method (Gilreath and Buchanan, 1981); Aron method (Aron,
1983); Dynamic method (Erez et al., 1979a,b), etc. However,
studies on heat requirements are fewer and the effects on flow-
ering are not well known (Couvillon and Erez, 1985; Citadin et
al., 2001; Gariglio et al., 2006).
Traditionally, hours below 7 ◦C or chilling hours (CH) have
been used as the measure of chilling for fruit trees (Weinberger,
1950). The Utah model, proposed by Richardson et al. (1974),
is used particularly in cooler areas of temperate zones (Dennis,
2003). This method quantifies the degree of accumulated chill-
ing in chill units (CU). Positive and negative hourly values
are accumulated at different rates for each temperature range.
Then, net values are added to obtain a specific CU accumulation
(Richardson et al., 1974). According to this method, the initial
date for CU calculation begins when chilling is consistent and
high temperatures are rare (Erez et al., 1979a).
The Dynamic model was proposed by Erez and Couvillon
(1987) and was developed for warmer areas than the Utah
model. Breakage of dormancy occurs in two steps, the first being
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Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
doi:10.1016/j.envexpbot.2008.01.003
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reversible and the second irreversible, and chilling requirements
are calculated as chilling portions (CP). As for the Utah model,
temperatures have different effects on dormancy. There is also a
negative influence of high temperatures, but temperature ranges
differ in the two models.
Like other temperate fruits, sweet cherry has chilling and heat
requirements for flowering. In recent years, many new sweet
cherry cultivars have been released and grown in different envi-
ronmental conditions. Some of them are early flowering, which
is a desirable character in Mediterranean areas to obtain early
yield. Although the south-east of Spain is an important fruit-
producing area, sweet cherry is not a traditional fruit crop in
the region of Murcia. However, nothing prevents this species
from being cultivated in different areas of Murcia with excellent
results, if appropriate varieties are chosen.
Little is known about the chilling requirements of sweet
cherry. Tabuenca (1983) determined the chilling requirements
of some sweet cherry cultivars growing in Zaragoza (Spain),
calculated as hours below 7 ◦C. Mahmood et al. (2000) studied
the chilling requirements of three medium-late-ripening sweet
cherry cultivars, estimating the chilling needs for each one. How-
ever, as far as we know, heat requirements have not been studied
in this species.
A consistent and predictable winter chilling accumulation in
a particular area is more desirable than year-to-year variability.
Knowledge of the chilling accumulation based on several years’
Table 1
Geographical characteristics and average chill units ±standard error, from data of 8–12 years in 42 weather stations in Murcia (south-eastern Spain)
No. Station County Latitude Longitude Altitude (m) Chill unit ±S.E.
1 AL31 Totana 37◦4359N1
◦3043W 296 1033 ±74
2 AL41 Alhama 37◦4812N1
◦40W 170 774 ±36
3 AL51 Librilla 37◦544N1
◦2013W 245 929 ±64
4 AL62 Mazarr´
on 37◦320N1
◦230W 15 335 ±48
5 CR12 Caravaca 38◦20N1
◦750W 880 1238 ±42
6 CR32 Cehegin 38◦30N1
◦400W 624 903 ±35
7 CR42 Moratalla 38◦1153N1
◦4843W 466 1158 ±41
8 CR52 Cehegin 38◦30N1
◦510W 527 1086 ±28
9 CA21 Murcia 37◦5013 N1
◦741W 120 904 ±74
10 CA42 Fuente Alamo 37◦450N1
◦741W 90 843 ±58
11 CA52 Cartagena 37◦4052N1
◦41W 120 765 ±74
12 CA72 Cartagena 37◦3748N0
◦5458W 70 794 ±67
13 CA91 Fuente Alamo 37◦4156N1
◦1417W 175 794 ±49
14 CI22 Abar´
an 38◦141N1
◦1821W 270 867 ±51
15 CI32 Ulea 38◦1128N1
◦1514W 306 995 ±72
16 CI42 Cieza 38◦1679N1
◦2779W 241 889 ±40
17 CI52 Calasparra 38◦1533N1
◦4347W 290 936 ±23
18 JU12 Jumilla 38◦2340N1
◦2530W 360 1223 ±34
19 JU42 Yecla 38◦3936 N1
◦1055W 661 1323 ±68
20 JU52 Yecla 38◦3345 N1
◦615W 690 1164 ±37
21 JU61 Jumilla 38◦280N1
◦190W 525 987 ±46
22 JU71 Jumilla 38◦340N1
◦140W 400 957 ±34
23 JU81 Jumilla 38◦200N1
◦190W 420 989 ±43
24 LO11 Lorca 37◦3611N1
◦371W 330 1061 ±72
25 LO21 Lorca 37◦3025N1
◦4142W 382 1172 ±69
26 LO31 Aguilas 37◦2512 N1
◦3528W 25 507 ±57
27 LO41 Lorca 37◦5140N1
◦4941W 697 1298 ±60
28 LO51 Aguilas 37◦2933 N1
◦3740W 180 723 ±60
29 LO61 Pto. Lumbreras 37◦355 N1
◦4244W 450 890 ±32
30 MO12 Torres de Cotillas 38◦050N1
◦1720W 169 830 ±77
31 MO22 Molina Segura 38◦72N1
◦1157W 150 765 ±54
32 MO31 Molina Segura 38◦40N1
◦140W 180 791 ±33
33 MO41 Abanilla 38◦105N0
◦256W 151 919 ±100
34 MO51 Fortuna 38◦958N1
◦853W 240 839 ±76
35 MO61 Ojos 38◦741N1
◦1952W 195 652 ±84
36 ML12 Yechar 38◦00N1
◦30W 320 876 ±55
37 ML21 Mula 38◦00N1
◦30W 320 697 ±81
38 MU21 Beniel 38◦27N1
◦028W 56 888 ±78
39 MU31 Murcia 37◦530N1
◦160W 150 573 ±78
40 MU52 Murcia 37◦5747N1
◦00W 210 675 ±52
41 MU62 Murcia 37◦5624N1
◦85O 140 853 ±90
42 TP81 Murcia 37◦4822N1
◦238O 153 973 ±87
Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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data would allow estimation of the probability of satisfying the
chilling requirements of sweet cherry cultivars in a given area.
The main goals of this work were to calculate the chilling
requirements for breaking the dormancy of seven sweet cherry
cultivars, using different methods (the hours below 7 ◦C, Utah
and Dynamic models), and to determine the heat requirements
for flowering in south-eastern Spain. With the estimated chill-
ing requirements and the knowledge of the chill accumulation
profile in this region during the last 8–12 years, the probability
of satisfying chill requirements in relation to the altitude was
determined for the sweet cherry cultivars studied in this work.
This information can be used to advise sweet cherry farmers
about which cultivars are best suited to their area and which
areas of our region are the most appropriate for sweet cherry
production.
2. Materials and methods
2.1. Plant material
The sweet cherry cultivars assayed were ‘Cristobalina’
(Spain), ‘Brooks’, ‘Ruby’ and ‘Marvin’ (California, USA),
‘Burlat’ (France), ‘New Star’ (Canada) and ‘Somerset’ (New
York, USA). The cultivars were chosen because they span the
range of flowering time in sweet cherry. All of them were cul-
tivated in Murcia (south-east Spain) under a Mediterranean
climate. Most of the cultivars were grown in an experimental
field located at Jumilla (see Table 1: station JU12 and Fig. 1),
with the exception of ‘Cristobalina’, which was grown in a pri-
vate orchard located at Abar´
an (see Table 1: station CI22 and
Fig. 1). All trees were grafted on ‘SL-64’ (Prunus mahaleb L.)
rootstock.
2.2. Determination of chilling and heat requirements
The chilling requirements necessary for breaking the dor-
mancy of each cultivar were calculated in the field as CH
(Weinberger, 1950), CU from the Utah method (Richardson et
al., 1974) or CP from the Dynamic model (Erez and Couvillon,
1987).
Heat requirements were calculated as growing degree hours
(GDH). GDHs are hourly average temperatures (◦C) minus
4.5 ◦C, accumulated daily (Richardson et al., 1974). For each
cultivar, heat requirements were calculated as the number of
GDHs accumulated between the end of dormancy and the date
when 50% of flowers were open (F50). Both chilling and heat
requirements were determined during two consecutive years
(2004–2006).
Hourly temperatures were provided by ‘Servicio de Infor-
maci´
on Agraria de Murcia’ (S.I.A.M.; http://www.carm.es/cagr/
cida/indexsiam.html). The meteorological stations were located
in the experimental field (Jumilla station, code JU12, see Table 1)
and very close to the private orchard (Abar´
an station, code CI22,
see Table 1). Table 2 shows maximum and minimum monthly
temperatures and rainfall during the autumn–winter season at
the sampling sites.
The geographical characteristics of 42 meteorological sta-
tions distributed throughout the region of Murcia and the average
CU (Utah method) for the data of 8–12 years ±standard error
are shown in Table 1.
Fig. 1. The location of Murcia in Spain (latitude 38◦45and 37◦23N; longitude 0◦41and 2◦21W) and the meteorological stations distributed in the region.
Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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Table 2
Temperatures, rainfall and chilling calculated by three models at Jumilla and Abar´
an (Murcia)
Date Temperature Rainfall (mm) Hours <7 ◦C Method chill units Portions
Mean Maximum Minimum
Jumilla
November/2004 10.0 13.4 5.5 1.9 162 138 11
December/2004 8.7 14.3 4.5 20.7 199 441 20
January/2005 6.1 12.9 −1.9 1.4 445 386 20
February/2005 6.6 14.9 2.6 13.6 370 223 26
March/2005 11.0 17.0 1.9 7.3 188 0 14
Total 1364 1188 91
November/2005 10.0 15.8 5.2 15.9 186 152 14
December/2005 7.7 13.0 4.1 5.5 319 448 26
January/2006 6.6 10.6 −2.3 46.7 367 525 21
February/2006 8.2 12.6 4.8 12.6 251 226 12
March/2006 13.5 19.3 7.6 0.3 74 0 19
Total 1197 1351 92
Abar´
an
November/2004 12.4 15.6 8.2 7.0 74 79 14
December/2004 10.5 15.8 5.8 41.8 104 373 21
January/2005 8.3 15.1 0.3 1.6 303 396 21
February/2005 8.6 18.2 3.8 20.9 262 206 19
March/2005 12.3 19.1 3.6 12.6 140 0 13
Total 883 1054 88
November/2005 12.0 18.8 7.9 26.6 79 138 14
December/2005 9.8 14.4 5.4 9.7 176 394 22
January/2006 8.3 11.8 0.7 46.0 225 496 18
February/2006 10.1 15.1 7.2 19.8 126 190 19
March/2006 15.3 20.5 8.8 0.8 26 0 11
Total 632 1218 84
Source: S.I.A.M. (http://siam.imida.es/).
With the data from all years, the probability that chilling
requirements would be satisfied was calculated as the percentage
of years with enough CU in each station to satisfy the chill-
ing requirements of every cultivar studied. This probability was
correlated with the altitude of each station.
2.3. Experimental design
During the 2 years of the study, four branches of each cul-
tivar (30cm length and 5 mm diameter, approximately) were
collected periodically from different trees. The first sample
was taken on December 15th and new branches were collected
when approximately 100 additional CU had accumulated. Sam-
ple collection was more frequent (approximately every 50CU
accumulated) when the accumulated chill became close to the
expected value (in most cases from the third collection) until the
middle of February.
In the laboratory, the bases of the branches were placed in
a 5% sucrose solution, in a growth chamber under controlled
conditions (24 ±1◦C, 55 mol m−2s−1, under cool white flu-
orescent tubes, and 70% relative humidity). After 10 days
in the growth chamber, the phenological stage of the flower
buds was tested using the methodology proposed by Baggiolini
(1952). The date for breaking of dormancy was established when
40–50% of flower buds were at the advanced Baggiolini stage B
(showing petals, Fig. 2) or at the phenological growth stage 55
according to the international BBCH scale (Meier et al., 1994).
Additionally, the weight of the flower buds was recorded after
10 days in the growth chamber. Rest was considered finished
when the weight of 20 flower buds increased by at least 20%
compared with the previous sampling (Guerriero et al., 2002).
2.4. Statistical analysis
Chilling and heat requirements data (CH, CU, CP and GDHs)
were subjected to analysis of variance (ANOVA), with culti-
var, year and model as sources of variation to estimate chilling
requirements. Means were separated by LSD (0.05). R2and the
linear regression functions were employed to determine the most
suitable model for chilling accumulation and the correlation
between average CU (Utah model), over 8–12 years, and the alti-
tude of the meteorological station. All analyses were performed
with the SPSS software package v. 11.0 for Windows.
3. Results
Weather data and CH, CU or CP accumulation during two
consecutive years at the experimental sites are presented in
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tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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Fig. 2. Phenological growth stages during flowering of sweet cherry according to Baggiolini (1952). Modified from Lichou et al. (1990).
Table 2. The chilling accumulation period in Murcia begins in
November, considering the first day of this period as the one after
the last negative accumulation (Richardson et al., 1974). The
Abar´
an station is at a lower altitude and is warmer than Jumilla,
with less average chill accumulation, calculated from at least 8
years data and by different methods (Table 1). In accordance
with this, the location had a strong influence on the accumulated
chill during 2005 and 2006 (P< 0.001) while the year did not
have any effect. Chilling values calculated by the three meth-
ods for the whole period studied differed (P< 0.001) (Table 2).
The interactions model–year and model–location were signif-
icant (P< 0.01 and P< 0.001, respectively). These differences
are mainly due to the results from the hours below 7 ◦C model,
which varied greatly between years and locations.
The increase in flower bud fresh weight recorded during the
first year of the experiment is shown in Fig. 3. The observed
increase coincided with the point when more than 50% of the
flower buds were at the advanced Baggiolini B stage, after 10
days at 24 ◦C for all cultivars with the exception of ‘Ruby’. For
this cultivar, an increase of flower bud weight was observed
between 700 and 800 CU; however, only after 800CU were
accumulated, had more than 50% of the flower buds reached
the B stage of Baggiolini.
Considering the increase in bud fresh weight and phenologi-
cal observations after 10 days in the laboratory, under controlled
conditions, differences in chilling requirements were not found
between years, but there were large differences among cultivars
(P< 0.001). The model and the interaction cultivar–model were
also significant (P< 0.001). In the climatic conditions of Murcia,
the chilling requirements ranged widely (Table 3). ‘Cristobalina’
was the first cultivar to break dormancy followed by ‘Brooks’,
Burlat’, ‘Ruby’ and ‘Somerset’ (with similar, medium chilling
requirements) whereas the highest chilling requirements were
observed for ‘New Star’ and ‘Marvin’.
Correlations between different methods were calculated with
the chilling requirement data. Statistical analysis indicated that
the Utah and Portions models are well related (Fig. 4A) and
differences between years were minor. However, the relationship
Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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Fig. 3. Fresh weight evolution of flower buds of the sweet cherry cultivars ‘Cristobalina’, ‘Brooks’, ‘Ruby’, ‘Marvin’, ‘Burlat’, ‘New Star’ and ‘Somerset’, as a
function of chilling accumulation (Utah model). Arrows indicate the break of dormancy. Bars represent the standard error.
between chilling requirements calculated as hours below 7 ◦C
and the Utah or Portions models depended on the year (Fig. 4B
and C).
Heat accumulation did not differ between years and a great
similarity was observed among cultivars, with values in a range
between 7326 and 9450 GDH (Table 3). Only ‘Ruby’ and ‘Mar-
vin’, with low and high heat requirements, respectively, differed
significantly from one another. Differences between years were
observed for some cultivars, such as ‘Cristobalina’.
There was a good correlation (R2= 0.629, linear regression
function: y= 700.29 + 0.71x) between CU, accumulated at the
42 stations within the region of Murcia, during several years,
and altitude for each station (Table 1).
Using the data for each cultivar, percentage of years with
enough CU to break rest was plotted against altitude of the sta-
tions (Fig. 5). The graphs were then divided vertically into 3
zones, I, II and III, representing a high, medium and low variabil-
ity of the probability to fulfil chilling requirements, respectively.
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tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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Table 3
Blooming dates, chilling and heat requirements of seven sweet cherry cultivars,
calculated at Abar´
an (Murcia) for ‘Cristobalina’ and at Jumilla (Murcia) for the
rest of the cultivars
Cultivar H < 7 ◦C Chill units Portions GDH Blooming
date
Cristobalina 176.0 a 397.0 a 30.4 a 9195.0 ab March 14th
Brooks 411.5 b 556.0 b 36.7 b 7863.2 ab March 27th
Ruby 618.0 c 806.0 c 48.0 c 7326.2 a March 29th
Somerset 618.0 c 806.0 c 48.0 c 8625.2 ab April 3rd
Burlat 618.0 c 806.0 c 48.0 c 8750.2 ab April 4th
New Star 709.5 cd 909.3 d 53.5 d 8257.0 ab April 4th
Marvin 788.0 d 1001.5 e 57.6 e 9449.7 b April 9th
Separation of cultivar means (lower-case letters) by the LSD test (P≤0.05).
Data are averages of two consecutive years.
Table 4
Land area as a function of altitude in Murcia
Altitude (m) Area (ha) Percentage Accumulated percentage
0–200 169,200 15 15
201–600 485,000 43 58
601–1000 364,100 32 90
1001–2000 113,000 10 100
>2000 0 0 100
Total: 1131,300
Source: Anuario Estad´
ıstico (http://www.carm.es/econet/publica/anuario/).
‘Cristobalina’ could be cultivated in almost every area of the
region with the exception of those close to the sea, because the
percentage of years in which its chilling requirements would be
satisfied is 100% at more than 175 m above sea level (Fig. 5).
With a very high probability, ‘Brooks’ would not have prob-
lems regarding the satisfaction of its chilling requirements above
325 m altitude. In our region, stations located above 450 m would
be appropriate for ‘Ruby’, ‘Somerset’ and ‘Burlat’. For ‘New
Star’ and ‘Marvin’, the limiting altitudes are 550 and 650 m,
respectively. The distribution of areas in Murcia according to
altitude is recorded in Table 4. All cultivars studied here could
be grown between 600 and 1000 m above sea level, where ful-
filment of their chilling requirements would be guaranteed. This
represents 32% of the total area of the region. Additionally, most
cultivars could be grown at much lower altitudes (up to 200 m),
representing 75% of the total area (Table 4).
4. Discussion
The Utah model has been used successfully in cool cli-
mates, whereas the Dynamic model seems to better indicate the
response of some fruit trees to chilling in warmer and/or sub-
tropical areas (Dennis, 2003). In this study, differences were not
found between these two models when estimating the chilling
requirements for seven sweet cherry cultivars in north-western
Murcia. They were used to calculate approximate flowering
dates, taking into account the cultivars’ heat requirements. Mean
temperatures during winter are moderate and negative chilling
values, generated with the Utah model, are not important, which
would explain the similarity to the results obtained with the
Fig. 4. Correlation between the chilling requirements of seven sweet cherry
cultivars, calculated as chill units (Utah model), CP and hours below 7◦C.
Dynamic model. However, the results obtained with the hours
below 7 ◦C model were not correlated with either the Dynamic
or the Utah model, suggesting that this model is not appropri-
ate for calculation of sweet cherry chilling requirements in our
Mediterranean climatic conditions.
Most work on the determination of chilling requirements in
sweet cherry has used the number of hours below 7 ◦C. It is
Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
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Fig. 5. Percentage of years that chilling requirement for sweet cherry cultivars
were satisfied in relation to the altitude where each meteorological station is
located, within the region of Murcia. The vertical, discontinuous lines separate
three different zones, I, II and III, representing a high, medium and low variability
of the probability to fulfil chilling requirements, respectively.
difficult to compare results obtained by different authors since
many factors need to be considered, such as the choice of plant
material, the criteria used to determine when rest is completed
or the environmental conditions during the previous growing
season (Dennis, 2003).
Tabuenca (1983) determined that the chilling requirements
of the early flowering cultivar ‘Cristobalina’ were 500–550h
below 7 ◦C, whereas in this study a value of only 176 h was
found for the same cultivar. Some authors have indicated that the
Californian cultivars ‘Brooks’, ‘Marvin’ and ‘Ruby’ have low
chilling requirements: 200–250 h below 7 ◦C(Marsall, 1990;
Herraiz, 1992; Ballester, 1992). Accordingly, we have found
that ‘Brooks’ had a low chilling requirement, estimated as CH,
CU or CP. However, we found different results for ‘Ruby’ and
‘Marvin’, which required medium and high chilling accumula-
tion, respectively, to break dormancy. Also, the requirements of
the cultivars ‘Ruby’ and ‘Marvin’, among others, were estimated
by the Utah method (Tersoglio et al., 2006) and the results are
in agreement with our findings for these two cultivars. ‘Ruby’,
with less than 950 CU, reached a normal budbreak and ‘Marvin’
needed more than 1000 CU. Erez (2000) reported that ‘Burlat’
had CP similar to those that we have estimated in our climatic
conditions.
In general, the heat requirements for flowering of the cherry
cultivars studied here were high (Table 3) compared with those
calculated in other Prunus species such as almond (Egea et
al., 2003; Alonso et al., 2005). In these studies, some almond
cultivars had less than 6000 GDHs (‘Desmayo Largueta’, ‘Con-
stantini’ or ‘Pou de Felanitx’). A recent work estimated that heat
requirements for ten apricot cultivars were under 5900 GDHs
(Ruiz et al., 2007). Our data show a narrow range of heat require-
ments, with a slight increase in the case of the late-flowering
cultivar ‘Marvin’. Spiegel-Roy and Alston (1979) suggested that
the chilling and heat requirements of pear (Pyrus communis L.)
are closely related to the time of bloom. Chill and heat require-
ments were found to be interdependent processes (Couvillon and
Erez, 1985) and an inverse relationship between the effects of
chilling and heat accumulation on the blooming time of peach
cultivars was found (Citadin et al., 2001). Greater chilling expo-
sures lead to a reduction of heat requirements. In almond, heat
requirements were found to be more important for regulation
of blooming time than were chilling requirements in the cold
climatic conditions of Zaragoza (north-east Spain), due to the
early completion of chilling (Alonso et al., 2005). However,
in south-east Spain, the flowering time of some almond culti-
vars was influenced more by chilling than by heat requirements
(Egea et al., 2003). In agreement with this, our results suggest
that differences in chilling requirements have a stronger influ-
ence on the blooming date than do heat requirements of sweet
cherry cultivars, in our climatic conditions, and that the average
blooming date of both years was earlier for cultivars with lower
chilling requirements but not for those with lower heat require-
ments, whereas the latest-blooming cultivar needed the highest
chill and heat accumulations to flower.
The results show a wide range of chilling requirements
for breakage of rest for the cultivars studied, which could be
grown successfully in specific areas of the region. This is sup-
Please cite this article in press as: Alburquerque, N., et al., Chilling and heat requirements of sweet cherry cultivars and the rela-
tionship between altitude and the probability of satisfying the chill requirements, Environmental and Experimental Botany (2008),
doi:10.1016/j.envexpbot.2008.01.003
ARTICLE IN PRESS
+Model
EEB-1874; No. of Pages 9
N. Alburquerque et al. / Environmental and Experimental Botany xxx (2008) xxx–xxx 9
ported by the fact that yields per hectare of sweet cherry in the
region of Murcia are well above average yields in other regions
of Spain (M.A.P.A., 2003, http://www.mapa.es/es/estadistica/
infoestad.html). Of great interest in Murcia are those cultivars
with low or medium chilling requirements, which produce early
harvests and fruits of high quality without the cracking prob-
lems, that are frequent in areas with abundant rains (Caprio and
Quamme, 2006).
Accumulated chilling is affected by the local geography,
especially the altitude in tropical and subtropical regions (Ou
and Chen, 2000). Accordingly, we have found a positive rela-
tionship between chilling accumulation and altitude of different
areas in our region. The probability of satisfying the chilling
requirements at different altitudes has been determined using cli-
matic information from several years. ‘Cristobalina’, ‘Brooks’,
‘Ruby’, ‘Burlat’ and ‘Somerset’ can be grown with a high prob-
ability of chilling requirement satisfaction in wide areas of our
region. ‘New Star’ and, particularly, ‘Marvin’ should be grown
only in the highest areas of our region, to avoid problems related
to lack of chilling. This is confirmed by the fact that all cultivars
growing in the experimental station, at 360 m above sea level,
flower without problems, with the exception of ‘Marvin’ which
frequently shows irregular blooming and yield. Knowledge of
the relationship between altitude and chill accumulation in dif-
ferent areas of our region, or at other locations, is of great interest
when deciding which sweet cherry cultivars to plant. Further
work could involve estimation of the chill and heat requirements
of more sweet cherry cultivars, to complete our knowledge of
the adaptability of this species to areas where its culture has not
been traditional.
Acknowledgements
Authors wish to thank Dr. Jose Egea and Dr. David Walker
for critical review of this manuscript. N. Alburquerque was sup-
ported by a postdoctoral contract “Juan de la Cierva” from the
Spanish Ministry of Education.
References
Alonso, J.M., Ans´
on, J.M., Espiau, M.T., Socias i Company, R., 2005. Determi-
nation of endodormancy break in almond flower buds by a correlation model
using the average temperature of different day intervals and its application
to the estimation of chill and heat requirements and blooming date. J. Am.
Soc. Hort. Sci. 130, 308–318.
Aron, R., 1983. Availability of chilling temperatures in California. Agric. Mete-
orol. 28, 351–363.
Baggiolini, M., 1952. Stade rep`
eres du pecher. Revue Romande d’Agriculture,
Viticulture et Arboriculture 4, 29.
Ballester, A., 1992. El cultivo del cerezo en la Comunidad Valenciana. Fruticult.
Prof. 49, 31–42.
Caprio, J.M., Quamme, H.A., 2006. Influence of weather on apricot, peach and
sweet cherry production in the Okanagan Valley of British Columbia. Can.
J. Plant Sci. 86, 259–267.
Citadin, I., Raseira, M.C.B., Herter, F.G., Baptista da Silva, J., 2001. Heat
requirement for blooming and leafing in peach. Hort. Sci. 36, 305–307.
Couvillon, G.A., Erez, A., 1985. Influence of prolonged exposure to chilling
temperatures on bud break and heat requirement for bloom of several fruit
species. J. Am. Soc. Hort. Sci. 110, 47–50.
Dennis Jr., F.G., 2003. Problems in standardizing methods for evaluating the
chilling requirements for the breaking of dormancy in buds of woody plants.
Hort. Sci. 38, 347–350.
Egea, J., Ortega, E., Martinez-Gomez, P., Dicenta, F., 2003. Chilling and heat
requirements of almond cultivars for flowering. Environ. Exp. Bot. 50,
79–85.
Erez, A., 2000. Bud dormancy; phenomenon, problems and solutions in the
tropics and subtropics. In: Erez, A. (Ed.), Temperate Fruit Crops in Warm
Climates. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp.
28–29.
Erez, A., Couvillon, G.A., 1987. Characterization of the influence of moder-
ate temperatures on rest completion in peach. J. Am. Soc. Hort. Sci. 112,
677–680.
Erez, A., Couvillon, G.A., Hendershott, C.H., 1979a. The effect of cycle length
on chilling negation by high temperatures in dormant peach leaf buds. J.
Am. Soc. Hort. Sci. 104, 573–576.
Erez, A., Couvillon, G.A., Hendershott, C.H., 1979b. Quantitative chilling
enhancement and negation in peach buds by high temperatures in a daily
cycle. J. Am. Soc. Hort. Sci. 104, 536–540.
Gariglio, N., Rossia, D.E.G., Mendow, M., Reig, C., Agusti, M., 2006. Effect of
artificial chilling on the depth of endodormancy and vegetative and flower
budbreak of peach and nectarine cultivars using excised shoots. Sci. Hort.
108, 371–377.
Gilreath, P.R., Buchanan, D.W., 1981. Rest prediction model for low chilling
“Songolds” nectarine. J. Am. Soc. Hort. Sci. 106, 426–429.
Guerriero, R., Viti, R., Monteleone, P., Gentili, M., 2002. la valutazione della
dormienza nell’albicocco: tre metodi a confronto. Frutticoltura 3, 73–77.
Herraiz, V., 1992. El cultivo del cerezo en la Comarca de la Almunia. Fruticult.
Prof. 49, 31–42.
Lichou, J., Edin, M., Tronel, C., Sounier, R., 1990. Le Cerisier. Ctifl, Paris.
Mahmood, K., Karew, J.G., Hadley, P., Battey, N.H., 2000. Chill unit models for
the sweet cherry cvs Stella, Sunburst and Summit. J. Hort. Sci. Biotechnol.
75, 602–606.
Marsall, J., 1990. Plantaciones intensivas o semi-intensivas de cerezo. Fruticult.
Prof. 30, 55–60.
Meier, U., Graf, H., Hack, H., Hess, M., Kennel, W., Klose, R., Mappes, D.,
Seipp, D., Stauss, R., Streif, J., Van den Boom, T., 1994. Ph¨
anologische
Entwick-lungsstadien des Kernobstes (Malus domestica Borkh. und Pyrus
communis L.), des Steinobstes (Prunus-Arten), der Johannisbeere (Ribes-
Arten) und der Erdbeere (Fragaria x ananassa Duch.). Nachrichtenbl. Deut.
Pflanzenschutzd. 46, 141–153.
Ou, S.K., Chen, C.L., 2000. Estimation of the chilling requirement and devel-
opment of a low-chill model for local peach trees in Taiwan. J. Chin. Soc.
Hort. Sci. 46, 337–350.
Richardson, E.A., Seeley, S.D., Walker, D.R., 1974. A model for estimating the
completion of rest for ‘Redhaven’ and ‘Elberta’ peach trees. Hort. Sci. 1,
331–332.
Ruiz, D., Campoy, J.A., Egea, J., 2007. Chilling and heat requirements of apricot
cultivars for flowering. Environ. Exp. Bot. 61, 254–263.
Spiegel-Roy, P., Alston, F.H., 1979. Chilling and post-dormant heat requirement
as selection criteria for late-flowering pears. J. Hort. Sci. 54, 115–120.
Tabuenca, M.C., 1983. Necesidades de fr´
ıo invernal de variedades de cerezo.
Anales Aula Dei 16 (3/4), 661–667.
Tersoglio, E., Naranjo, G., Rivero, L., Quiroga, M., 2006. Requerimiento de fr´
ıo
invernal y de calor en variedades de cerezos. ITEA 102, 251–259.
Weinberger, J.H., 1950. Chilling requirements of peach varieties. Proc. Am. Soc.
Hort. Sci. 56, 122–128.
