９愛媛大学農学部紀要（Mem. Fac. Agr., Ehime Univ.）
５
１：９−１３（２００６）

Effect of Summer Pruning on Shoot Growth and Fruit Qualityin Peach Trees Trained as Slender Spindle Bush Type
A.B.M. Sharif HOSSAIN＊, Fusao MIZUTANI＊, Justus M. ONGUSO＊, A.R. El-SHEREIF＊ and K.L. RUTTO＊
Abstract
Summer pruning experiments were carried out to maintain slender spindle bush type in ‘Hikawahakuho’ peach(Prunus persica Batsch) trees grafted on wild form vigorous rootstocks. In the first experiment in which five-year-oldtrees were used, summer pruning was performed in mid-July after fruit were harvested, while winter pruning in midMarch as the control. Summer pruning produced regeneration of terminal and lateral shoots. Terminal shoot growth
was greater than lateral shoot. Leaf chlorophyll content (SPAD value) was greater but the percentage of flower buds
was lower in summer-pruned than winter-pruned trees. In the following season, the total shoot length was greatly
reduced in summer pruned trees. Fruit maturation seemed to be accelerated in summer-pruned trees, which resulted inhigher soluble solids content (SSC) and lower titratable acidity (TA) in the fruit. Furthermore, in the second
experiment, effects of two successive years of summer pruning were determined. The weight of pruned shoots waslower in the two-successive-year-summer-pruned (SP") trees than single-year-summer-pruned (SP!) trees. Thissuggests the gradual reduction in the vegetative growth of trees by annual summer pruning. SSC of fruit was slightly
higher in SP" than SP! trees. Thus, summer pruning in mid-July after fruit harvest is a useful practice formaintaining slender spindle bush type of peach trees grafted on vigorous rootstocks.
Key words: Dwarfing, Flower bud, Shoot growth, Slender spindle bush, Summer pruning.

Introduction
Slender spindle bush types are commonly applied oncompact-sized fruit trees. Peach trees grafted on Prunus
tomentosa and some other Prunus species can be dwarfed
but show graft-incompatibility (Ferree, 1988; Andrews
and Serrano, 1992). It is difficult to maintain trees graftedon vigorous rootstocks as slender spindle types by winterpruning. The growth of current-year shoots is so great thatthe inner parts of the trees are shaded resulting in poor
growth and even death of shoots near the trunk. Suchpoor light penetration also causes poor fruit pigmentation.
Moreover, the vigorous shoot growth competes with fruit
growth eventually affecting the quality of harvested fruit.
A number of reasons have been given to support thepractice of summer pruning in peach. Summer pruning
was reported to reduce vegetative growth, improve light
penetration, enhance fruit quality, concentrate fruit
maturation and increase the number of flower buds
(Hyden and Emerson, 1976; Ritter, 1983; Rom andFerree, 1984). Summer pruning has been regarded as lessinvigorating than dormant pruning (Hyden and Emerson,1976; Utermark, 1977).
Received 27 March 2006.
Accepted 22 June 2006.
＊Laboratory of Agricultural (Biological) Production Management, The Experimental Farm, Faculty of Agriculture, EhimeUniversity, 498 Ko, Hattanji, Matsuyama, 799-2424, Japan

Summer pruning has recently received much attention
as a potential method of controlling tree size and reducing
pruning costs in orchard operations (Taylor and Ferree,1984). It may, however, alter tree physiological processesin ways that are not yet fully understood (Rom andFerree, 1984; Taylor and Ferree, 1986; Marini, 1985).
Summer pruning of woody plants has resulted in alteredlevels of endogenous growth regulators and shootcarbohydrates (Rom and Ferree, 1984). In the previouswork, we reported that summer pruning was a usefulpractice for maintaining slender spindle bush type byusing an early maturing selection (‘Akatsuki’ x unknown‘Banto’) peach trees grafted on vigorous rootstocks(Hossain et al., 2004). Here we further studied theusefulness of summer pruning for maintaining slender
spindle bush type by using another early maturing peach
cultivar ‘Hikawahakuho’ grafted on vigorous wild form
peach rootstocks.
Materials and Methods
Experiment ISiteThe experiment was carried out in an orchard in theEhime University Farm located in southern Japan, 33°57′,N, 132°47′, E at an elevation of about 20 m above sea
level. The area has a mild temperate climate characterizedby hot humid summers and cold dry winters. The averageannual temperature and precipitation are 14.5℃ and 1,200mm, respectively.

１０A.B.M. Sharif HOSSAIN, Fusao MIZUTANI, Justus M. ONGUSO, A.R. El-SHEREIF and K.L. RUTTO

Plant materials, treatment and measurement
Five-year-old peach (Prunus persica Batsch cv.
‘Hikawahakuho’) trees grafted on wild form vigorous
peach rootstocks and planted at a spacing of 2 x 3 m wereused. They had been trained as slender spindle bush typeby winter pruning before the experiment started. Eighttrees were randomly selected and four trees each subjected
to summer and winter pruning respectively. Summer
pruning consisted of heading back of current shoots toabout 10 cm length and removal of vigorous shoots,
which was conducted after fruit harvest on July 15, 2003.
On the other hand, winter pruning was done in early
March 2004. The number of regenerated shoots wasrecorded starting after summer pruning and the terminal
and lateral shoot length was measured for four months.
The other parameters such as leaf drop percent, vegetativeand flower bud number were determined. Leaf chlorophyll
was measured in early September and early November
2003 using a SPAD chlorophyll meter (SPAD-502,Minolta Co. Japan). Leaves were selected in the middle
part of regenerated shoots in the summer-pruned trees andof current-year shoots in the winter-pruned trees. In 2004,
the total shoot length was measured before summer
pruning. Fruit were harvested on June 28, 2004. Fruit
number per tree and fruit weight were recorded
immediately after harvest. Ten fruit per tree wererandomly selected and used to determine total soluble
solids content (SSC) and titratable acidity (TA).
Experiment II
Plant materials, treatment and measurement
In 2004, another group of six-year-old ‘Hikawahakuho’peach trees grafted on vigorous wild form peachFig. 1. Effect of summer pruning on pruned branch weight ofpeach trees in 2003−2004. SP＝summer pruning; WP＝winter pruning. Vertical bars represent SE (n＝4).
Summer-pruned branches include leaves.

rootstocks were selected from the same plots ofExperiment! and a similar experiment was conductedagain. Summer pruned trees were designated as SP! andwinter pruned trees as WP!. Moreover, the trees used inExperiment! were successively summer and winterpruned in the second season. These trees were designatedas SP" and WP", respectively. In 2004, summer
pruning was conducted on July 15 after fruit harvest,
while winter pruning in early March 2005. The number ofregenerated shoots was counted after summer pruning, andthe weight of pruned branches was also recorded. Fruit
were harvested on June 29, 2005. Fruit number per tree
and fruit weight were recorded immediately after harvest
and SSC and TA were determined.
Results
Experiment I
The pruned shoot weight was higher in summer-pruned
than in winter-pruned trees (Fig. 1). Shoot regeneration
started one week after pruning and stopped by midSeptember (Fig. 2). The growth of regenerated shoots wasobserved to continue up to mid-October (Fig. 3). There
was no difference in leaf chlorophyll content (SPADvalues) in September but in November the content was
higher in summer-pruned than in winter-pruned trees (Fig.
4). Leaf drop started two months earlier in winter-pruned
than in summer-pruned trees (Fig. 5). There were fewer
flower buds in summer-pruned trees than winter-prunedtrees (Table 1). In the following year, the total shootlength of summer-pruned trees was approximately half ofthat of winter-pruned trees (Table 1). There were nosignificant differences in fruit number per tree, fruit
weight, or yield between the two treatments (Table 2).
However, soluble solids content (SSC) of harvested fruit
was greater and titratable acid content (TA) lower inFig. 2. Effect of summer pruning conducted in mid-July on
regenerated shoot numbers of peach trees in 2003.
Vertical bars represent SE (n＝4).

Effect of Summer Pruning on Shoot Growth and Fruit Quality in Peach Trees Trained as Slender Spindle Bush Type

１１Fig. 5. Effect of summer pruning on leaf drop in peach trees
from late September to late January in 2003−2004.
Vertical bars represent SE (n＝4).

Fig. 3. Effect of summer pruning on average regenerated shootlength of peach trees in 2003. Vertical bars represent
SE (n＝4).

Fig. 6. Effect of summer and winter pruning on pruned shootweight of peach trees in 2004. Vertical bars represent
SE (n＝4). SP＝Summer pruning, WP＝Winterpruning. Summer-pruned branches include leaves. SP!, WP! and SP", WP" indicate single-year andtwo-successive-year pruning, respectively.

Fig. 4. Effect of summer pruning on leaf chlorophyll of peachtrees in September and November in 2003. Verticalbars represent SE (n＝4).

Table 1. Effect of summer pruning on flower bud formationand total shoot length of peach trees in thefollowing year 2004.
Treatment
SPWP

summer-pruned than in winter-pruned trees (Table 2).
Experiment II
In 2004, there was little difference in pruned shootweight between SP! and WP!. However, the pruned
shoot weight was lower in SP" than SP! (Fig. 6). Fruit
number per tree was a little lower in summer-pruned thanZFlower buds(%)
z17.2±4.5 z
65.7±8.7

Total shoot length(m)21.8±4.945.0±9.0

Mean ± SE (n＝4)

in winter-pruned trees in both single-year and twosuccessive-year treatments (Table 3). However, the fruit
diameter was slightly greater in summer-pruned trees but

１２

A.B.M. Sharif HOSSAIN, Fusao MIZUTANI, Justus M. ONGUSO, A.R. El-SHEREIF and K.L. RUTTO

Table 2. Effect of summer pruning on yield and quality of peach fruit in the following year 2004.
Treatment

Fruit No./treez

SPWPz

10.8±5.8 z
15.7±1.1

Fruit weight(g)Yield(kg/tree)

Soluble solids
content (%)

Titratable acidity(%)

146.5±12.9137.4±15.4

1.66±0.84
2.18±0.08

11.04±0.26
10.25±0.26

0.37±0.05
0.54±0.04

Mean ± SE (n＝4)

Table 3. Effect of summer and winter pruning on fruit yield and quality of peach in 2005.
Fruit
No./treeFruit weight Fruit diameter Fruit length(g)
(mm)
(mm)

Yield(kg/tree)

Maturitydegreez

Soluble solids Titratable
content (%) acidity (%)

28.1±4.1x
41.1±5.822.2±3.630.4±4.3

131.0±0.5
128.1±0.4
136.2±6.0
128.6±0.4

3.7±0.75.3±1.0
3.0±0.6
3.9±0.8

3.5±0.4
2.7±0.2
3.9±0.3
2.9±0.3

12.8±0.24
11.8±0.21
13.7±0.25
12.7±0.20

Treatment
SP!yWP!
SP"WP"yx

62.8±0.660.5±0.463.6±0.760.6±0.561.7±0.659.6±0.362.8±0.659.7±0.4

0.27±0.03
0.39±0.03
0.24±0.02
0.38±0.03z

Maturity degree was determined visually by giving a score of 0 (green skin color) to 5 (red fully ripen) depending on fruit
maturity.
ySP＝Summer pruning, WP＝Winter pruning. SP!, WP! and SP", WP" indicate single-year and two-successive-year
pruning, respectively.
xMeans ± SE (n＝4).

there were no significant differences in yield per tree.
Table 3 shows that SSC of harvested fruit was greater andTA lower in summer-pruned than in winter-pruned trees,
when compared within single-year treatments (SP! andWP!) and two-successive-year treatments (SP" and WP"). Furthermore, SSC was greater and TA was lower inSP" than SP!.
Discussion
In Experiment!, the pruned shoot weight was higher
in summer-pruned than in winter-pruned trees (Fig. 1).
This is probably because summer pruning was conducted
for the first time, and because summer-pruned branches
included leaves. The growth of regenerated shoots
continued up to mid-October reaching a mean length of
14.7cm. Marini (1984) reported that only 2% of theshoots in summer-pruned peach trees exhibited re-growthwith mean re-growth length being 7.3 cm. It seems thatthe growth of regenerated shoots depends on the time ofsummer pruning. Mizutani et al. (2000) reported that theearlier summer pruning resulted in the greater shoot lengthand shoot numbers in apple trees. Summer pruned trees
showed greater leaf chlorophyll content (SPAD values) inNovember (Fig. 4). Mierowska et al. (2002) also reported
that in apple spur leaves total chlorophyll content was
higher in summer-pruned than in non-pruned trees during
November-March.
Summer pruning caused the reduction in flower budformation (Fig. 6). Mizutani et al. (2000) reported adecrease in flower bud formation with delayed summer
pruning in apple trees. Hossain et al. (2004) stated thatflowers were less in summer-pruned than in winter-pruned
trees, and that bud-break occurred three to four days
earlier in summer-pruned compared with winter-prunedtrees. Erez (1982) observed that in a mechanized meadow

orchard system of peach trees, four to five months arerequired for sufficient shoot regeneration and flower bud
formation. Therefore, he insists that the system can beapplicable to only early maturing cultivars, with a longenough growing season after fruit harvest.
Ferree et al. (1984) reported that re-growth increases
when pruning is done early in the growing season. Thisobservation may be due to changes in phytohormone
levels with time within the growing season. We reported
that SSC was higher and TA was lower in summer-pruned
than in winter-pruned trees by employing ‘Akatsuki’ x
unknown ‘Banto’ peach selection (Hossain et al. 2004).
The increasing SSC and lowering TA were found in trees
after two-successive-year summer pruning in thisexperiment (Table 3). This tendency was also observed in
the previous work (Hossain et al., 2005).
In conclusion, summer pruning in mid-July after harvest
may be a useful practice for controlling tree size in earlymaturing cultivar peach trees grafted on vigorousrootstocks in which slender spindle bush type training isapplied.
Acknowledgements
The authors are grateful to Ministry of Education,Culture, Sports, Science and Technology, Japan forproviding funds for this work.
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摘要

A.B.M. シャリフ フセイン・水谷房雄・J.M. オングソ・
A.R. エル‐シェリフ・K.L. ルット：細型紡錘形に仕立てた
強勢台モモ樹における枝の生長，果実品質に及ぼす夏季剪定の効果
強勢台木の野生モモに接いだ５年生の 日川白鳳 を用いて，樹形を細型紡錘形に維持するために，夏季剪定の実験を行った．果実が収穫された後，７月中旬に夏季剪定を行った．一方，対照区として冬季剪定は３月中旬に行った．夏季剪定によって，頂芽や側芽からの２次新梢の発生が見られた．側芽からの２次新梢に比べて頂芽からの２次新梢のほうが生長が良かった．冬季剪定に比べて，夏季剪定区のほうが葉のクロロフィル含量（SPAD値）が高かったが，花芽の割合が低かった．翌年，夏季
剪定区で全枝長が小さくなった．果実の成熟は夏季剪定
区で促進される傾向が見られ，その結果，夏季剪定区で果実の糖度は高く，酸度は低かった．さらに，続いて２年連続の夏季剪定の効果を調査した．２年連続して夏季剪定をすると，剪定枝重は単年だけの夏季剪定区に比べて，小さくなった．これは，連年の夏季剪定によって樹体の栄養生長が抑制されていることを示すものと思われる．また，連年の夏季剪定によって果実の糖度はやや高くなる傾向が認められた．したがって，果実収穫後の７月中旬の夏季剪定は，強勢台木に接いだモモを細型紡錘形に維持するのに有効な管理だと思われる．