Scientia Horticulturae 114 (2007) 275–280
www.elsevier.com/locate/scihorti
Effect of synthetic auxins on fruit development of ‘Bing’ cherry
(Prunus avium L.)
Raphael A. Stern a,*, Moshe Flaishman b, Steve Applebaum c, Ruth Ben-Arie d
b
a
MIGAL, Galilee Technology Center, P.O. Box 831, Kiryat-Shmona 11016, Israel
Institute of Horticulture, ARO, The Volcani Center, P.O. Box 6, Bet-Dagan 50250, Israel
c
Kibbutz Ortal, Golan Heights 12430, Israel
d
Fruit Storage Research Laboratory, Kiryat-Shmona 10200, Israel
Received 29 April 2007; accepted 9 July 2007
Abstract
The main cherry cultivar grown in the warm climate of Israel, ‘Bing’, produces relatively small fruit. Over three consecutive years (2003–2005),
application of 50 mg l 1 2,4-dichlorophenoxypropionic acid [2,4-DP; as its butoxyethyl ester (PowerTM)], 10 mg l 1 3,5,6-trichloro-2-pyridyloxyacetic acid [3,5,6-TPA; as the free acid (Maxim1)], or 25 mg l 1 2,4-dichlorophenoxyacetic acid (2,4-D) plus 30 mg l 1 naphthaleneacetic
acid (NAA; 0.3% AmigoTM), at the beginning of pit-hardening when fruitlet diameter was ca. 13 mm caused appreciable and significant increases
in fruit size and total yield, except when the crop load was heavy. Anatomical studies revealed that the main effect of these synthetic auxins was via
direct stimulation of fruit cell enlargement. The above auxins had no negative effect on fruit quality, either at harvest or after 1 month of storage at
0 8C, or on return yield in the following year.
# 2007 Elsevier B.V. All rights reserved.
Keywords: Auxins; Cherry; Fruit size; Prunus avium L.
1. Introduction
Small fruit size is one of the limiting factors in marketing
cherry (Prunus avium L.) fruit (Sansavini and Lugli, 2005;
Whiting and Ophardt, 2005). As consumers prefer large
cherries, fruit size is a very important marketing consideration,
and the economic benefits of treatments capable of improving
average fruit size are potentially very high. Several techniques
have been used to improve fruit size of cherry. Among them,
bloom and fruit thinning have been proven to be effective
(Proebsting, 1990). Whiting and Lang (2004) showed that a
negative relationship exists between the ratio of fruit number to
leaf area and the size of the sweet cherry fruit. However, the
commercial application of chemical bloom or fruitlet thinning
of sweet cherry has not yet been reported in the literature and no
products are currently registered for this purpose (Byers et al.,
2003; Whiting and Ophardt, 2005). Synthetic auxins may be
effective in enhancing fruit growth, when applied during the
second stage of fruit development (Faust, 1989; Westwood,
* Corresponding author. Tel.: +972 4 6953508; fax: +972 4 6944980.
E-mail address: [email protected] (R.A. Stern).
0304-4238/$ – see front matter # 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.scienta.2007.07.010
1993). These auxins are known for their ability to increase cell
enlargement (Westwood, 1993; Arteca, 1996; Davis, 2004),
thus enhancing fruit growth in certain species such as Citrus
(Agusti et al., 1995), peach (Agusti et al., 1999; Flaishman,
2006), litchi (Stern et al., 2000), apricot (Agusti et al., 1994)
and loquat (Agusti et al., 2003). In all species so far studied,
synthetic auxin had the potential for increasing fruit size
without inducing thinning.
In Citrus, peach and litchi, it was found that application of
the synthetic auxin 3,5,6-trichloro-2-pyridyloxyacetic acid
(3,5,6-TPA), at concentrations between 10 and 20 mg l 1,
considerably increased fruit size, whereas in apricot and loquat,
2,4-dichlorophenoxypropionic acid (2,4-DP) at 25–50 mg l 1
had the optimum effect.
Application of 2,4,5-trichlorophenoxypropionic acid (2,4,5TP) was in commercial use, in stone fruit and litchi orchards in
Israel, until its registration was withdrawn.
Since no report has been published as to the effect of
synthetic auxins on fruit size of sweet cherry, the objective of
this study was to evaluate the effects of some synthetic auxins
on fruit development, size, maturation, quality and yield in
‘Bing’ sweet cherry.
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R.A. Stern et al. / Scientia Horticulturae 114 (2007) 275–280
2. Material and methods
2.1. The orchards
Experiments were conducted between 2003 and 2005 on
mature cherry ‘Bing’ trees grafted on ‘Mahaleb’ (Prunus
mahaleb L.) rootstock, in three orchards:
(1) At Merom-Golan, located 900 m above sea level (a.s.l.) on
the Golan Heights, where the trees were 2.5 m high, spaced
at 2.5 m 4.5 m (880 trees ha 1).
(2) On the Fichman Experiment Station, located 1000 m a.s.l.
on the Golan Heights, where the trees were 3.0 m high,
spaced at 2.5 m 4.5 m (880 trees ha 1).
(3) At Ortal, located 1100 m a.s.l. on the Golan Heights, where
the trees were 3.0 m high, spaced at 3.0 m 5.0 m
(670 trees ha 1).
All orchards are located in a semi-arid area with high
temperatures (ca. 35 8C max.) and low humidity (<40% RH)
during the summer (May–October). Average annual precipitation (November–April) is approximately 900 mm. The soil is
0.8 m deep, and classed as a well-drained basaltic protogromosol (65% clay) on basaltic rocks. The soil pH is 7.7 with a
CaCO3 content of approximately 7% (w/w). The irrigation
system consisted of two lateral lines per row, separated by
1.0 m, with 1.6 l h 1 pressure compensated in-line drippers
(Netafim, Iftach, Israel) space at 0.5 m. Since yield of ‘Bing’ is
usually low, no thinning treatments were applied.
2.2. Auxin application
Three commercial products, containing different synthetic
auxins, were applied: (1) Maxim1 tablets containing 10% (w/
w) 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA; Dow
AgroScience, Madrid, Spain); (2) PowerTM, a liquid formulation containing 5% (w/v) 2,4-dichlorophenoxypropionic acid
(2,4-DP butoxyethyl ester; Fine Agrochemicals, Whittington,
UK); (3) AmigoTM, a liquid formulation containing 0.8% (w/v)
2,4-D isopropyl ester plus 1% (w/v) naphthaleneacetic acid
(NAA); Lainco, Barcelona, Spain.
The synthetic auxins were applied as foliar sprays at
different concentrations at 2 l tree 1 using a high-pressure
handgun (Kibbutz Degania 15130, Israel) until run-off. A nonionic surfactant, Triton X-100, was included in all sprays at
0.025% (v/v). Applications were made at the beginning of pithardening (25 days after full bloom = DAFB), when the
fruitlets had reached a diameter of ca. 13 mm in all
experiments. The experiments were conducted on whole trees
bearing a uniform crop load according to the fruit set at that
moment. Control trees, with the same crop load, were not
sprayed.
The experimental design was a randomised complete block,
with eight replications of one tree per treatment. In each
experiment, the fruits were harvested twice based on the
commercial measurement—mahogany color (Crisosto et al.,
2003). At harvest, the yield from each tree was weighed and all
fruit were manually sorted by diameter: small (<22 mm),
medium (22–26 mm) or large (>26 mm). Semi-commercial
trials were conducted in 2005 at Merom-Golan (880 trees ha 1)
and Ortal (670 trees ha 1) using a commercial (1000 l) air-blast
‘‘spidet’’ sprayer (Kibbutz Degania 15130, Israel) at a rate of
1500 l ha 1. In Merom-Golan, each tree received 1.7 l of the
solution, while in Ortal, each tree received 2.2 l. This was a
randomised complete blocks experimental design with four
replicates. Each replicate consisted of 10 trees. At harvest, total
yield and average fruit size were determined for all 10 trees.
2.3. Fruit growth
In Merom-Golan orchard (in 2004) and Ortal orchard (in
2005) ten 1-year-old limbs bearing one typical fruit were
selected on each tree. Development of 40 fruit (10 fruit per
tree 4 trees) per treatment was monitored from the day of
treatment until harvest by periodically measuring the diameter
of each fruit on the selected limbs.
2.4. Fruit characteristics at harvest and after storage
Maturity at harvest and keeping quality in storage of fruit,
sampled at the peak of the commercial harvest in the MeromGolan orchard (2004), were examined for two of the auxin
treatments and the control. Two representative samples of ca.
1 kg of the predominant size (26 mm) were selected from the
fruit harvested from two trees in each of three replicates per
treatment. For assessment of ripening, sub-samples of 10 fruit
from each batch were subjected to measurement of color and
extraction of the juice by squeezing in muslin for assay of
soluble solid content (SSC) and titratable acidity (TA). Color
readings were performed with a calibrated Minolta CR-200
chromameter, using the L*, a*, b* coordinates of the CIELAB
system. Chroma (C) and hue angle (H8) were calculated from
a* and b*. SSC was measured with a digital refractometer
(Atago Co. Ltd., Tokyo, Japan). Two millilitres of aliquots of
the extracted juice were titrated with 0.1 M NaOH to pH 8.2 to
assess TA, expressed as g malic acid equivalent 100 g 1 fruit
flesh. For quality assessment, the remaining fruit were
examined either on the same day or after storage. Stored fruit
was pre-cooled to 0 8C, wrapped in polyethylene bags and held
at this temperature for 3 weeks. Fruit examination consisted of
sorting fruit for defects, such as decay, pitting, cracking and
shrivel, in this order. Fruit that had none of these defects were
considered healthy. Fruit with more than one of the defects fell
into the more severe category, according the order described
above.
2.5. Anatomical analysis
Cell size was measured on sections prepared from five
representative fruit, uniform in size (26 mm) and color
(mahogany), harvested from each treatment applied to the
Merom-Golan orchard in 2004. For histological examinations,
fruits were fixed in FAA solution [50% (v/v) ethanol; 10% (v/v)
formaldehyde; 5% (v/v) acetic acid; 35% (v/v) H2O] at room
R.A. Stern et al. / Scientia Horticulturae 114 (2007) 275–280
temperature for at least 3 weeks. The fixation did not change the
tissue size. Fixed tissue samples were then dehydrated in a
graded series of six H2O:ethanol:tert-butanol (TBA) solutions,
from 10 to 100% TBA. Tissue samples were immersed for 12 h
in each of the first five solutions, than three times for 24 h each
in the sixth solution [100% (v/v) TBA] before being embedded
in Paraplast plus (Oxford Labware, St. Louis, MO, USA).
Sections were cut at 10–15 mm thickness using a rotary
microtome (American Optical, Buffalo, NY, USA), stained in
safranin and Fast Green (Stern et al., 1996) and mounted with a
glass cover slip using Microscopy Entellan (Merck, Darmstadt,
Germany). Sections were examined and photographed using a
Leitz Dialux 20 light microscope (Flaishman et al., 2005). The
number and type of cells for each fruit were determined from
the photographs of the mesocarp parenchymatic cells. Five
counts of the number of cells for a given length were made
midway between the pit and the skin. The average cell size was
calculated by dividing the given length by the number of cells.
2.6. Return bloom and yield
In Merom-Golan orchard (in 2004), five limbs of 50 cm each
were selected on each of the 50 mg l 1 2,4-DP (PowerTM)treated, 25 mg l 1 2,4-D plus 30 mg l 1 NAA (AmigoTM)treated, 10 mg l 1 3,5,6-TPA (Maxim1)-treated and untreated
control trees. In the following spring (2005), inflorescences of
7–10 flowers were counted on the selected limbs, and the yield
per tree was determined.
2.7. Statistical analysis
Percentage data were subjected to arcsine transformation
before analysis, to provide a normal distribution. Data were
analyzed for statistical significance, by means of the general
linear model (GLM) procedure. Duncan’s new multiple range
test was used to compare treatments when ANOVA showed
significant differences among means.
277
Fig. 1. Effect of 10–100 mg l 1 2,4-DP on the yield of large (>26 mm) ‘Bing’
cherry fruit. All treatments were applied at pit-hardening using handgun
sprayer, at Fichman Experiment Station in 2003. Data are the means of eight
trees per treatment. Different letters denote significant differences between
means according to Duncan’s new multiple range test, P = 0.05.
30 mg l 1, respectively, (as 0.3% AmigoTM) in different
orchards and added another synthetic auxin—3,5,6-TPA at
10 mg l 1. Again, the results showed the advantage of all three
auxins. All treated fruit grew at a faster rate and were larger
than untreated control fruit with no statistical difference
between the auxins (Fig. 3). This was expressed in the yield of
large fruit (Fig. 4), which was more or less doubled by all three
treatments (increased from 3 to 6–7 kg tree 1). Since none of
the treatments caused any fruit thinning, the total yield was also
increased from 20 kg tree 1 for the control trees to almost
30 kg tree 1 on the treated trees. The effect of all auxins in
increasing fruit size as well as enhancing color, advanced
commercial harvest by about 4 days (Table 1). At the first
harvest, a higher proportion of the fruit was picked from trees
treated with auxins than from the control, although the
difference was not statistically significant.
In the third year (2005), we re-examined the auxin effect in
semi-commercial trials conducted in two orchards: MeromGolan and Ortal. In each orchard only one of the two best
treatments was applied—25 mg l 1 2,4-D and 30 mg l 1 NAA
[0.3% (v/v) AmigoTM] in Merom-Golan or 50 mg l 1 2,4-DP
3. Results
3.1. Fruit size and yield
In the first year (2003), 2,4-DP at the intermediate
concentration of 50 mg l 1 and [2,4-D + NAA] at concentrations of 25 and 30 mg l 1, respectively, [0.3% (v/v) AmigoTM],
increased fruit size and total yield (Figs. 1 and 2). The increase
in the yield of large fruit was 65% with 50 mg l 1 2,4-DP
(6.4 kg tree 1 vs. 3.9 kg tree 1 in the control), while with lower
or higher concentrations, there were slight decreases in yield
(Fig. 1). [2,4-D + NAA], which were applied only as 0.3%
AmigoTM (25 mg l 1 2,4-D + 30 mg l 1 NAA), showed a
considerable shift to larger sized fruit (Fig. 2). This auxin
had the greatest effect on total yield (40 2.8 kg tree 1 vs.
27 3.1 kg tree 1 in the control) and on fruit size
(13 kg tree 1 large fruit vs. 3.9 kg tree 1 in the control).
In the second year (2004), we re-examined the effect of 2,4DP at 50 mg l 1 and [2,4-D + NAA] at 25 mg l 1 plus
Fig. 2. Effect of 25 mg l 1 2,4-D + 30 mg l 1 NAA (0.3% AmigoTM) on fruit
size distribution of ‘Bing’ cherry fruit. The treatments were applied at pithardening, using handgun sprayer at Fichman Experiment Station in 2003. Data
are the means of eight trees per treatment. Different letters on bars denote
significant differences between the means for each size group according to
Duncan’s new multiple range test, P = 0.05.
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R.A. Stern et al. / Scientia Horticulturae 114 (2007) 275–280
Table 1
Effect of different synthetic auxins on the rate of fruit ripening, as indicated by
the time of commercial harvest
Auxin treatment (mg l 1)
3,5,6-TPA (10)
2,4-DP (50)
2,4-D + NAA (25 + 30)
Control
P
Fruits harvested (%) a
27/5
31/5
52.3
55.5
55.7
48.8
N.S.
47.7
44.5
44.3
51.2
N.S.
The fruit was harvested according to the commercial color standard.
a
Fruits harvested expressed as percentage of total fruits per tree harvested at
the two indicated dates.
Fig. 3. Effect of 50 mg l 1 2,4-DP, 25 mg l 1 2,4-D + 30 mg l 1 NAA [03% (v/
v) AmigoTM] and 10 mg l 1 3,5,6-TPA on diameter (mm) of ‘Bing’ cherry fruit.
The treatments were applied at pit-hardening (April 20; 25 days after full
bloom = DAFB), using a handgun sprayer at Merom-Golan in 2004. Data are
the means of 40 fruit (10 fruit per tree, 4 trees per treatment). Different letters
denote significant differences between means according to Duncan’s new
multiple range test, P = 0.05.
(PowerTM 50) in Ortal. We were unable to achieve any
considerable positive effect on fruit size in Merom-Golan, since
the total yield from all trees was very high that year, above
40 kg tree 1 (Table 2). However, in Ortal orchard, the ‘Bing’
yield was normal (ca. 30 kg tree 1), and again the advantage of
the auxin treatment, 50 mg l 1 2,4-DP, was readily apparent.
This was expressed as a faster growth rate (Fig. 5) and, as a
result, above 60% increase in the yield of large fruit (from
6 kg tree 1 in the control to 10 kg tree 1 in the auxin
treatment).
In the third year (2005), we recorded the return yield on the
experimental trees used in the second year at Merom-Golan. No
further treatments were applied in 2005, and there were no
differences between the total yields and fruit size distribution
among all treatments (Table 3).
Fig. 4. Effect of 25 mg l 1 2,4-D + 30 mg l 1 NAA [0.3% (v/v) AmigoTM],
50 mg l 1 2,4-DP and 10 mg l 1 3,5,6-TPA on total yield and the yield of large
(>26 mm) ‘Bing’ cherry fruit. The treatments were applied at pit-hardening,
using a handgun sprayer at Merom-Golan in 2004. Data are the means of eight
trees per treatment. Different lowercase or uppercase letters denote significant
differences between means according to Duncan’s new multiple range test,
P = 0.05.
Table 2
Effect of 25 mg l 1 2,4-D + 30 mg l 1 NAA (0.3% AmigoTM) at Merom-Golan
orchard or 50 mg l 1 2,4-DP (PowerTM) at Ortal orchard on fruit size and yield
of ‘Bing’ cherry fruit in 2005
Orchard
Auxin treatment
(mg l 1)
Total yield
(kg tree 1)
Yield of large
fruit (>26 mm)
(kg tree 1)
Merom-Golan
2,4-D + NAA
(25 + 30)
Control
43 a
11 a
45 a
10 a
2,4-DP (50)
Control
33 a
28 a
10 a
6b
Ortal
The auxins were applied at pit-hardening with a commercial ‘‘Spidet’’ blower
sprayer.
Data are the means of 40 trees (10 trees 4 replicates) per treatment.
Means within a column in each orchard followed by a different letter differ
significantly according to Duncan’s new multiple range test, P = 0.05.
3.2. Cell enlargement in the fruit
Microscopic observation was made on the sizes and types of
the mesocarp cells of treated and untreated fruit. Parenchymal
cell sizes showed were increased by all auxin treatments
compared to those of control fruit (Fig. 6). However, there were
some differences between the auxins: 2,4-D + NAA had the
greatest effect, with an increase of more than 25% in cell size,
Fig. 5. Effect of 50 mg l 1 2,4-DP on diameter (mm) of Bing’ cherry fruit. The
treatments were applied at pit-hardening (May 1; 25 days after full bloom = DAFB), using a commercial ‘‘Spidet’’ blower sprayer at Ortal in 2005. Data are
the means of 40 fruit (10 fruit per tree, 4 trees per treatment). Different letters
denote significant differences between means according to Duncan’s new
multiple range test, P = 0.05.
R.A. Stern et al. / Scientia Horticulturae 114 (2007) 275–280
Table 3
Effect of 25 mg l 1 2,4-D + 30 mg l 1 NAA (0.3% AmigoTM), 50 mg l 1 2,4DP (PowerTM) or 20 mg l 1 3,5,6-TPA during 2004 on the return bloom, yield
and fruit size of ‘Bing’ cherry in 2005 at Merom-Golan
Auxin treatment in
2004 (mg l 1)
Inflorescences
(no./50 cm limb)
Total yield
(kg tree 1)
Yield of large
fruit (>26 mm)
(kg tree 1)
2,4-D + NAA (25 + 30)
2,4-D (50)
3,5,6-TPA (10)
Control
10
12
11
10
35
32
36
33
14
12
15
13
a
a
a
a
a
a
a
a
a
a
a
a
The auxins were applied at pit-hardening with a hand gun sprayer.
Data of the return bloom (no. of inflorescences) are the means of 40 limbs (5
limbs 8 replicates). Yield data are the means of 8 trees per treatment.
Means within a column in each orchard followed by a different letter differ
significantly according to Duncan’s new multiple range test, P = 0.05.
while 3,5,6-TPA and 2,4-DP were less effective (although still
significant).
3.3. Fruit quality and maturity at harvest
There was no effect of treatments on the quality or the
maturity of the fruit at harvest. Fruit quality was impaired
equally in all treatments by the occurrence of cracking, at a rate
of 14 1%. The indices of maturity, color, SSC and TA also
remained unaffected by either of the two treatments for which
the fruit was evaluated (Table 4), in spite of the significantly
accelerated growth rate of the fruit (Fig. 3). During storage fruit
quality deteriorated due to the development of pitting, without
significant differences between treatments.
4. Discussion
One of the limiting factors in stone fruit development is the
low supply of assimilates to the fruit, especially with a heavy
yield (Faust, 1989; Westwood, 1993). The dependence of fruit
growth on assimilate availability has been demonstrated with
peach, by reducing vegetative growth using growth retardants
Fig. 6. Effect of 3 25 mg l 1 2,4-D + 30 mg l 1 NAA [03% (v/v) AmigoTM],
50 mg l 1 2,4-DP and 10 mg l 1 3,5,6-TPA on cell enlargement (mm) in the
fruit mesocarp of Bing’ cherry fruit. Treatments were applied at pit-hardening,
using a handgun sprayer at Merom-Golan in 2004. Data are the means of five
fruits per treatment (26 mm size), which were picked at the peak of the harvest
(of each treatment). Different letters denote significant differences between
means according to Duncan’s new multiple range test, P = 0.05.
279
Table 4
Effect of different synthetic auxins on fruit maturity and quality at harvest
Auxin treatment (mg l 1)
Control
2,4-DP (50)
2,4-D + NAA (25 + 30)
Fruit colora
L
C
H8
SSC (%)
TA (%)
33.9
32.5
31.8
23.6
24.2
23.4
16.6
15.4
14.7
17.3
16.1
17.5
0.67
0.62
0.63
The fruit was harvested according to the commercial color standard.
a
CIELAB coordinates (see Section 2).
(Blanco, 1987) or girdling (Dann et al., 1984). Both treatments
can modify the source–sink relationship and carbohydrate
partitioning between plant organs and favour fruit growth
instead of vegetative growth (Goren et al., 2004). An additional
factor that can promote the sink potential of the fruit is the auxin
level in the fruit, which is in direct proportion to the rate of fruit
growth (Crane, 1964). Miller et al. (1987) found two peaks of
indol-3-acetic acid (IAA) concentration in the peach mesocarp,
separated by a period of low IAA concentration. The first peak
precedes the cell division phase (Stage I) in the mesocarp, while
the second peak precedes the cell enlargement phase (Stage III).
The lowest concentration of IAA occurs at the beginning of pithardening (Stage II), which indicates the onset of the growth lag
phase.
Treatment with a synthetic auxin, such as 3,5,6-TPA in
peach (Agusti et al., 1999) or 2,4-DP in apricot (Agusti et al.,
1994) increased fruit size. Similar treatment with 3,5,6-TPA in
citrus raised the carbohydrate level in the fruit and as a result
increased fruit size (Agusti et al., 2002).
The litchi fruit, although not belonging to the stone fruit
family, bears a pit in which a decline occurs in the endogenous
IAA level at the ‘heart stage’ of the embryo, which evidently is
the cause of extensive fruitlet abscission (Stern and Gazit, 2000,
2003). Exogenous application of 2,4,5-TP or 3,5,6-TPA at this
stage not only reduced abscission, but also directly accelerated
the rate of fruit growth due to the increase in sink strength
(Stern et al., 2000).
To the best of our knowledge no attempt has so far been made
to increase the size of sweet cherry fruit by application of
synthetic auxins. The increase in cell size demonstrated here in
response to auxin application at the pit-hardening stage (Fig. 6),
may indicate their ability to stimulate carbohydrate translocation
to the fruit in combination with their effect on increasing cell wall
elasticity (Arteca, 1996). As a result of increased cell size, the
growth rate of the fruit was enhanced (Fig. 3) with a final overall
increase in fruit size and yield. The increase in fruit size appears
to be a direct result of increased sink strength and not an indirect
effect, such as a result of reduced vegetative growth or increased
fruit abscission. The lack of an effect on fruit size when the auxins
were applied to heavy bearing trees (2005), as opposed to the
positive response obtained when yields were normal (2003 and
2004), emphasizes the dependence of fruit size on carbohydrate
production. Auxin enhancement of the sink potential of the fruit
will only be of benefit to fruit size, when the carbohydrate supply
is sufficient for the fruit load. At loads in excess of 35 kg/tree,
auxin will be of little value, as it cannot be used as a replacement
for fruit thinning.
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R.A. Stern et al. / Scientia Horticulturae 114 (2007) 275–280
In peach trees, similar auxin treatment increased sink
strength and stimulated the rate of fruit growth and accelerating
maturation so that the fruit size was the same at commercial
basis as of the control (Agusti et al., 1999). The same
phenomenon with peach cv. ‘Oded’ was recently reported by
Flaishman (2006) in Israel. However, in case of the cherry, the
auxin treatments accelerated the rate of fruit growth just for 3–4
days (Table 1) and maturation was not advanced according to
most of the maturity measurements (Table 2).
In conclusion, our results show that application of 50 mg l 1
2,4-DP (PowerTM), 10 mg l 1 3,5,6-TPA (Maxim1) or
25 mg l 1 2,4-D + 30 mg l 1 NAA (0.3% AmigoTM) at the
beginning of pit-hardening stimulated cell enlargement in the
mesocarp of ‘Bing’ cherry fruit, which in turn, caused a
significant improvement in fruit size and total yield (provided
the crop load was not too heavy). No negative effects on fruit
thinning, ripening or return yield were discerned for these three
auxins.
This work was supported by an Israeli Ministry of Agriculture
and Rural Development Grant (No. 596-0238-03) and by the JCA
Charitable Foundation. We thank Moshe Agiv and Nurit BarSinai for valuable technical assistance and Alla Zvilling and Asia
Gizis for valuable assistance in the measurements of fruit
ripening in the Fruit Storage Research Laboratory.
References
Agusti, M., Juan, M., Almela, V., Speroni, C., 1994. The effect of 2,4-DP on
fruit development in apricots (Prunus armeniaca L.). Sci. Hort. 57, 51–57.
Agusti, M., El-Otmani, M., Juan, M., Almela, V., 1995. Effect of 3,5,6trichloro-2-pyridyloxyacetic acid on clementine early fruitlet development
and on fruit size at maturity. J. Hort. Sci. 70, 955–962.
Agusti, M., Almela, V., Andreu, I., Juan, M., Zacarias, L., 1999. Synthetic auxin
3,5,6-TPA promotes fruit development and climacteric in Prunus persica L.
Batsch. J. Hort. Sci. Biotechnol. 74, 556–660.
Agusti, M., Zaragoza, S., Iglesias, D.J., Almela, V., Millo, E.P., Talon, M., 2002.
The synthetic auxin 3,5,6-TPA stimulates carbohydrate accumulation and
growth in citrus fruit. Plant Growth Regul. 36, 141–147.
Agusti, M., Gariglio, N., Castillo, A., Juan, M., Almela, V., Martinez-Fuentes,
A., Mesejo, C., 2003. Effect of the synthetic auxin 2,4-DP on fruit
development of loquat. Plant Growth Regul. 41, 129–132.
Arteca, R.N., 1996. Plant Growth Substances: Principles and Applications.
Chapman and Hall Press, New York, USA, 332 pp.
Blanco, A., 1987. Fruit thinning of peach trees (Prunus persica L. Batsch): the
effect of paclobutrazol on fruit drop and shoot growth. J. Hort. Sci. 62,
147–155.
Byers, R.E., Costa, G., Vizzoto, G., 2003. Flowers and fruit thinning of peach
and other prunus. Hort. Rev. 28, 351–392.
Crane, J.C., 1964. Growth substances in fruit setting and development. Annu.
Rev. Plant Physiol. 15, 303–326.
Crisosto, C.H., Crisosto, G.M., Metheney, P., 2003. Consumer acceptance of
‘Brooks’ and ‘Bing’ cherries is mainly dependent on fruit SSC and visual
skin color. Postharvest Biol. Technol. 28, 159–167.
Dann, I.R., Wildes, R.A., Chalmers, D.J., 1984. Effect of limb girdling on
growth and development of competing fruit and vegetative tissues of peach
trees Prunus persica. Aust. J. Plant Physiol. 11, 49–58.
Davis, P.J., 2004. The plant hormones: their nature, occurrence and functions.
In: Davis, P.J. (Ed.), Plant Hormones. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 1–15.
Faust, M., 1989. Physiology of Temperate Zone Fruit Trees. Wiley, New York,
USA, pp. 169–234.
Flaishman, M., 2006. Development of stone fruit for export. Annual Report for
the Chief Scientist. Ministry of Agriculture, Bet-Dagan, Israel (in Hebrew),
65 pp.
Flaishman, M., Shargal, A., Shlizerman, L., Lev-Yadun, S., Stern, R.A., Grafi,
G., 2005. The synthetic cytokinins CPPU and TDZ prolong the phase of
cell division in developing pear (Pyrus communis L.) fruit. Acta Hort. 671,
151–157.
Goren, R., Huberman, M., Goldshmidt, E.E., 2004. Girdling: physiological and
horticultural aspects. Hort. Rev. 30, 1–36.
Miller, A.N., Walsh, C.S., Cohen, J.D., 1987. Measurements of indole-3-acetic
acid in peach fruits (Prunus persica L. Batsch. cv. Redhaven) during
development. Plant Physiol. 84, 491–494.
Proebsting, E.L., 1990. The interaction between fruit size and yield in sweet
cherry. Fruit Varieties J. 44, 169–172.
Sansavini, S., Lugli, S., 2005. Trends in sweet cherry cultivars and breeding in
Europe and Asia. In: Proc. 5th Int. Cherry Symposium. Bursa, Turkey,
(Abstract), p. 1.
Stern, R.A., Gazit, S., 2000. Reducing fruit drop in lychee with PGR
sprays. In: Basra, A. (Ed.), Plant Growth Regulators in Agriculture
and Horticulture. The Haworth Press Inc., New York, USA, pp. 211–
222.
Stern, R.A., Gazit, S., 2003. The Reproductive Biology of the Lychee. Hort.
Rev. 28, 393–453.
Stern, R.A., Eisenstein, D., Voet, H., Gazit, S., 1996. Anatomical structure of
two day old litchi ovules in relation to fruit set and yield. J. Hort. Sci.
Biotechnol. 71, 661–671.
Stern, R.A., Stern, D., Harpaz, M., Gazit, S., 2000. Applications of 2,4,5-TP
3,5,6-TPA and combinations thereof increases lychee fruit size and yield.
HortScience 35, 661–664.
Westwood, M.N., 1993. Temperate-Zone Pomology: Physiology and Culture,
third ed. Timber Press, Portland, OR, USA, 523 pp.
Whiting, M.D., Lang, G.A., 2004. ‘Bing’ sweet cherry on the dwarfing rootstock
‘Gisela 5’: thinning affects tree growth and fruit yield and quality but not net
CO2 exchange. J. Am. Soc. Hort. Sci. 129, 407–415.
Whiting, M.D., Ophardt, D., 2005. Comparing novel sweet cherry crop load
management strategies. HortScience 40, 1271–1275.