MINISTRY OF EDUCATION AND TRAINING
CAN THO UNIVERSITY
LE BAO LONG
“STUDY ON FACTORS CAUSING INNER
GAMBOGE DISORDER IN MANGOSTEEN
(Garcinia mangostana L.)”
Maior: Crop Science
Code: 62-62-01-10
SUMMARY OF DOCTORAL DISSERTATION
Can Tho - 2015
The dissertation was completed at: College of Agriculture and Applied
biology – Can Tho University
Scientific supervisors:
Ass. Prof. LE VAN HOA
Ass. Prof. NGUYEN BAO TOAN
Opponent 1:
Opponent 2:
Opponent 3:
The dissertation will be presented at university level
Time……………………………………Date…………………………………
Further information of the dissertation could be found at:
1. Learning Resource Center – Can Tho University
2. National library of Vietnam
1
OVERVIEW OF THE THESIS
1.1 The necessity
Mangosteen is called “the Queen” of fruits because of its qualities
such as delicous, nutritious, popular and having great export potential, etc.
However, through the experience of cropping mangosteen of farmers in Cho
Lach district – Ben Tre province and Cau Ke district – Tra Vinh province, it
showed that high yield and good quality are necessary to gain high profits
from mangosteen fruits; but the investigation and survey results of Nguyen
Minh Hoang and Nguyen Bao Ve (2008) showed that the gamboge disorder
ratio in mangosteen was rather high, fruit harvested early in the beginning of
the season rarely had gamboge disorder but the ratio of gamboge disorder
highly increased at the end of the season, it was up to 100% when it was
excess rain and it was one of the most interest problems of farmers cropping
mangosteen fruit trees in Vietnam as well as in all over the world. Therefore,
it is essential to study on factors causing inner gamboge disorder and to
suggest possible practices.
1.2 Research objectives
The study aims to determine factors that lead to the fruit gamboge
phenomenon and suggest possible practices to reduce inner gamboge
disorder in mangosteen fruits.
1.3 Subjects and scope
Study subjects are mainly mangosteen fruit trees of different ages
grown from seeds at farmers’ orchards in Cho Lach district – Ben Tre
province and Cau Ke district – Tra Vinh province.
Major scope of the study are some factors related to and practices to
prevent the incidences of inner gamboge disorder in mangosteen fruits.
1.4 New contributions
Inner gamboge disorder fruits had lower Ca2+ and pectin of cell-wall
content in fruit-flesh than those in the normal ones; CaCl2 as foliar spraying
reduced inner gamboge disorder ratio since Ca2+ increased pectin
composition in cell-wall.
2
Internal pressure of fruit caused by growing segments (especially for
the uneven growing segments) or the formation of seed containing apomictic
embryos was not even. It caused damages and broke latex secretory ducts at
the core of fruit and aril; GA3 as foliar spraying increased inner gamboge
disorder ratio by increasing the thickness of fruit peel and reducing pectin
content in cell-wall of fruit-flesh when harvest
Sudden increase of soil moisture before harvesting increased inner
gamboge disorder ratio due to water absorption of fruit and latex;
Minimizing sudden increase of soil moisture before harvesting reduced inner
gamboge disorder ratio.
1.5 Practical and scientific significances
Scientific significances: the study results provided specific scientific
basis about causes of inner gamboge disorder in mangosteen fruits. The
results can be used as additional material of coursebook and reference for
further studies of fruit trees.
Practical significances: effective application in production, contribute
to improve mangosteen fruit’s yield and quality, increase farmers’ income.
Chapter 3
MATERIALS, CONTENT AND METHODOLOGIES
3.1 Research materials
Mangosteen fruit trees of different ages were experimented at farmers’
orchards in Cho Lach district – Ben Tre province and Cau Ke district – Tra
Vinh province, all were grown from seeds. Measuring and analysis
instruments: refractometer (model ATAGO, Japan), pH meter (model
ORION 420A, USA), spectrometer (model Shimadzu UV-1201, Japan),
...Chemical application on flowering: HVP super (Thiourea 99%, Technical
Services Joint Stock Company in Ho Chi Minh City), KClO3 (99,5%;
China), Paclo 10WP (Paclobutrazol 10%, Dong Thap Agricultural Service
Company Limited),…Foliar fertilizer and plant groưth regulators: CaCl2
(96%, China), Bioted 603 (Vinh Long Technological Development
Company), gibberellic and naphthalene acetic acid (China),…Analysis
3
chemicals: CH3OH, EDTA-Na4 (C10H12N2Na4O8.2H2O), NaBH4, (C2H5)2,...
(China and Germany), ….
3.3 Research content
3.3.1 Survey of the incidences inner gamboge disorder in
mangosteen fruits
3.3.1.1 Morphological characteristics and physical - biochemical
characteristics of mangosteen fruits in growing process
The experiments began in 3/2011 when mangosteen fruit trees were
completely flowering and finished in 6/2011. Fruit samples were collected
randomly from 30 trees aged from 20 - 25 years in one orchard in Long Thoi
commune – Cho Lach district – Ben Tre province. The survey aimed to find
out about inner gamboge disorder time and relationship between
morphological and physiological-biochemical characteristics with the
incidences of inner gamboge disorder in fruits.
3.3.1.2 Physical-biochemical characteristics of normal mangosteen
and inner gamboge disorder fruit
Fruit samples were collected randomly from 35 trees of different ages
(from 15 to 25 years) in a orchard in Long Thoi commune – Cho Lach
district – Ben Tre province in 2011 crop season. The survey aims to
determine the differences of physical-biochemical characteristics between
normal mangosteen and inner gamboge disorder fruits.
3.3.1.3 Ability to identify inner gamboge disorder fruits
The survey was carried out in Cho Lach district – Ben Tre province in
2012 crop season. Four groups of the survey subject consisted of traders,
orchard owners, sellers, and customers. Each participating subject was
required to sellect 30 inner gamboge disorder fruits. The survey aims to find
out about the relationship between external morphological characteristics and
the incidenes of inner gamboge disorder through ability to identify of each
group.
4
3.3.1.4 Relationship between plant age and the incidences of inner
gamboge disorder
It included two experiments: the first experiment to investigate the
correlation of plant age with the ratio of inner gamboge disorder in fruit was
carried out on 6 orchards with trees of different ages (10 - 15, 20 – 25, 30 –
35, 40 – 45, 50 - 55, and over 60 years old), the second experiment to
investigate physical–biochemical characteristics of mangosteen fruits from
young and old trees was carried out on 5 trees aged 10 – 15 years old and on
5 trees over 50 years old in one orchard under the same care regime. Both
experiements were executed in Long Thoi commune – Cho Lach district –
Ben Tre province in 2012 crop season. The survey aims to find out the
relationship between plant age and the incidences of inner gamboge disorder.
3.3.2 Survey on factors caused inner gamboge disorder in
mangosteen fruit
3.3.2.1 The relationship between fruit physical characteristics and the
incidences of inner gamboge disorder
The survey aims to find out about the relationship between physical
characteristics of fruit and the incidences of inner gamboge disorder,
including two eperiments as follows:
* Correlation of physical characteristics with the incidences of inner
gamboge disorder
Fruit samples were collected to survey physical-biochemical
characteristics of normal and inner gamboge disorder fruits, at the same time
the sample were used to survey the correlation with the incidences of inner
gamboge disorder in fruits
* Effect of gibberellic and naphthalene acetic acid as foliar spraying
on the incidences of inner gamboge disorder
The experiment was carried out in the orchard had stable fruit
production (20 - 25 years old) in Long Thoi commune – Cho Lach district –
Ben Tre province in 2012 crop season. The experiment design was
completely randomized, including 7 treatments with six replications for each
5
treatment, and each of which equal to one tree. The treatments included no
chemical application (water spraying), GA3 or NAA from 25 to 100 ppm.
Foliar spraying with GA3 and NAA were applied after completed flowering
in 1 month with 8 liters.tree-1, spraying 4 times with 15-day invervals.
3.3.2.2 Effect of soil moisture on the incidences of inner gamboge
disorder
The survey aims to determine the relationship between soil moisture
before harvesting and the incidences of inner gamboge disorder, including
three experiments:
* Relationship between changes of soil moisture before harvesting
with the incidences of inner gamboge disorder
The experiment started in 3/2011 when mangosteen trees were
completely flowering and ended in 6/2011 on 6 mangosteen trees aged from
20 – 25 years in one orchard in Long Thoi commune – Cho Lach district –
Ben Tre province.
* Effect of timing of artificial water stress
The experiment started in 3/2011 when mangosteen trees were
completely flowering and ended in 6/2011 in the orchard of 23-year-old
mangosteen trees had stable fruit production in Long Thoi commune – Cho
Lach district – Ben Tre province. The experiment design was completely
randomized, including 4 treatments with four replications for each treatment,
each of which equal to one tree. The treatments were timing of artificial
water stress after completed flowering 0.5; 1.5; 2.5; and as soon as fruit
achieved level-0 color index according to the standard of MOA (2002).
* Effect of the frequency of artificial water strees
The experiment started in 3/2012 when mangosteen trees were
completely flowering and ended in 6/2012 in the orchard of 24-year-old
mangosteen trees had stable fruit production in Long Thoi commune – Cho
Lach district – Ben Tre province. The experiment design was completely
randomized, including 5 treatments with four replications for each treatment,
each of which equal to one tree. The treatments were the number of water
6
stress times when the trees were completely flowering 2.5 months: control
(without treating artificial water stress), 1, 2, 3 and 4 times. The first water
stress when completed flowering 2.5 months, for multiple treatments of
water stress, the next treatment will be conducted after 7 days.
3.3.2.3 Survey on the relationship of calcium content in soil and
fruit with inner gamboge disorder ratio
The experiment was conducted on 30 mangosteen orchards had stable
fruit production (20 - 25 years old) in Long Thoi commune – Cho Lach
district – Ben Tre province in 2013 crop season. The survey aims to find out
about the correlation of calcium conten in soil and fruit with the incidences
of inner gamboge disorder.
3.3.3 Survey on practices to prevent the incidences of inner gamboge
disorder
3.3.3.1 Survey on inducing early flowering
The experiment was carried out on 14-year-old mangosteen orchard in
Phu Tan commune – Cau Ke district – Tra Vinh province in 2010/2011 crop
season. The experiment design was completely randomized, including 7
treatments with 3 replications for each treatment, each of which equal to one
tree. The treatments: control (water spraying), time of spraying thiourea (1,
2, and 3 months) after drenching PBZ 2 g a.i./m or KClO3 40 g a.i./m in
canopy diameter. The experiment aims to determine the effect of flowering
time on the incidences of inner gamboge disorder
3.3.3.2 Study on additional organic fertilizer application
The experiment was carried out on mangosteen orchard (24 years old)
had stable fruit production in Phu Tan commune – Cau Ke district – Tra
Vinh province in 2010/2011 crop season. The experiment design was
completely randomized, including 5 treatments with 4 replications for each
treatment, each of which equal to one tree. Each treatment corresponded with
the dosages of organic fertilizer for each tree: 0, 10, 20, 40, và 80 kg.tree-1.
The experiment aims to determine the effect organic fertilizers on the
incidences of inner gamboge disorder.
7
3.3.3.3 Study on irrigation regime
The experiment was carried out on mangosteen orchard (20 – 25 years
old) had stable fruit production in Long Thoi commune – Cho Lach district –
Ben Tre province in 2012/2013 crop season. The experiment design was
completely randomized, including 3 treatments with 5 replications for each
treatment, each of which equal to one tree. The treatments included: nontreated, transparent plastic cover after completed flowering 2 months, and
non-treated - watering 2 days/once – 50 liters/tree/time. The experiment aims
to determine the effect of irrigation regime on the incidences of inner
gamboge disorder.
3.3.3.4 Additional of calcium chloride as foliar spraying
The experiment was carried out on mangosteen orchard with trees
aged 20 - 25 years old in Long Thoi commune – Cho Lach district – Ben Tre
province in 2013/2014 crop season. The experiment design was completely
randomized, including 9 treatments with 4 replications, each of which equal
to one tree. Calcium chloride was sprayed over the leaf canopy with the
dosage of 8 liters.tree-1 beginning at flowering and 8 weeks after flowering,
spray 4 times with 15-day interval. Control treatment was conducted without
chemical application (water spraying), other treatments had CaCl2 content
from 0.25% - 2.0%. The experiment aims to determine the effect of calcium
chloride as foliar spraying on the incidences of inner gamboge disorder.
3.4 Research methodologies
3.4.3 Data analysis and statistics
Microsoft Excel was used to analyze data and draw graphs. Analysis of
variance and independent sample T-Test were used to find out the differences
between treatments and analysis the correlation by the use of SPSS version
20.0; means were compared by verification of LSD and Duncan.
8
Chapter 4
RESULTS AND DISCUSSION
4.1 Survey on the incidences of inner gamboge disorder in
mangosteen fruits
4.1.1 Morphological characteristics, physiological–biochemical
characteristics in growing process
4.1.1.1 Exterior and inner morphological characteristics of
mangosteen fruits
Large and small segments together appear inside the fruit, large
segments with or without apomictic embryo, the number of stigma lobes
corresponds exactly with the number of fruit segments (Fig. 4.2).
Fig. 4.2 Inner morphology of mangosteen fruit (1: large segment containing embryo,
2: large segment containing embryo, 3: small segment)
Latex secretory ducts moved from stalk to inside fruit (Fig. 4.4A),
yellow latex secretory ducts arranged in peel, fruit-flesh, the core of fruit,
and around aril (Fig. 4.4B), ducts were branched as canal-like type without
specific structure (Fig. 4.4C). The results showed that latex secretory ducts
were easily influenced.
Fig. 4.4 The distritution of latex vessels inside fruit (A: longitudinal section, B:
cross-section, C: latex secretory ducts)
9
4.1.1.3 Inner gamboge disorder time
The inner gamboge disorder appeared 8 weeks after completed
flowering (Fig. 4.13). Growth segments (embryos) and heavy rain were
factors related to the inner gamboge phenomenon.
Inner gamboge disorder ratio (%)
50
No. seed contain
embryo1 (seed)
1.6
40
1.2
30
0.8
20
0.4
10
0
0
2
4
6
8
10
12
Inner gamboge disorder1
ratio (%)
No. embryo
2
TH
Time after full flowering (week)
Fig. 4.13 The formation of seed containing apomictic embryo and inner gamboge
disorder in growing process ( : ± standard deviation)
Fig. 4.18 showed that growing segment affected latex vessels at the
core of fruit, after completed flowering until 6 weeks showed that the core of
fruit was normal (Fig. 4.18A), the core of fruit was affected by a slight
impact after 8 weeks (Fig. 4.18B), after 10 weeks the core of fruit was
curved (Fig. 4.18C) and this broke latex secretory ducts. Dorly et al. (2008)
and Poerwanto et al. (2009) also had similar consideration. Fig. 4.19 showed
that there were great changes of rainfall in growing period; Limpawiphagorn
(1998) and Chutimunthakun (2001) also stated that excess water during preharvest usually caused the incidences of inner gamboge disorder.
Fig. 4.18 Longitudinal section of mangosteen in various growing period (A: the core
of normal fruit, B: wristed core of the fruit, C: curvature of the fruit core)
Rainfall (mm)
10
Growth
stage
Developing
Growth and harvesting
Fig. 4.19 Daily rainfall and growing period of mangosteen fruits in Long Thoi
commune – Cho Lach district – Ben Tre province in 2011 crop season
4.1.2 The incidences of gamboge disorder, physical – biochemical
characteristics of inner gamboge disorder and normal developed
mangosteen fruits at harvest
4.1.2.2 Physical–biochemical characteristics of inner gamboge
disorder and normal mangosteen fruits at harvest
The weight of inner gamboge disorder fruits were higher and peel
thicker than those of normal developed, significant difference (Tab. 4.2). The
level of pectin in cell-wall of fruit-flesh of the inner gamboge disorder fruits
were 1.33 folds lower than those in the normal ones (Tab. 4.3).
Tab. 4.2 Physical – biochemical characteristics of inner gamboge disorder and
normal mangosteen fruits from trees of different ages (15 to 25 years) in Long Thoi
commune – Cho Lach district – Ben Tre province in 2011 crop season.
Parameters
Weight
Size
Quality
Fruit weight (g)
PTV (%)
Peel thickness (mm)
CCCR ODNM1
o
Brix
Fruit
Inner gamboge disorder
71.6±0.88
75.2±0.25
8.6±0.06
0.223±0.01
15.1±0.1
Normal
67.7±0.52
71.6±0.18
8.0±0.04
0.242±0.06
16.1±0.1
T-test
**
**
**
*
**
Data were expressed as mean ±SE; * significant difference 5% by T-Test; **: significant difference 1%
by T-Test; PTV: the percentage of peel weight, CCCR ODNM1: the ratio of latex secretory duct
height/width in large segment position.
11
Tab. 4.3 Cell-wall composition of inner gamboge disorder and normal fruits from
mangosteen trees of different ages (15 to 25 years) in Long Thoi commune – Cho
Lach district – Ben Tre province in 2011 crop season.
Extract ingredients
Extract with distilled
water (mg.g-1)
Pectin (mg.g-1)
Sugar type
Neutral sugar
Acidic sugar
Neutral sugar
Acidic sugar
Hemicellulose (mg.g-1) Neutral sugar
Acidic sugar
Cellulose (mg.g-1)
Total sugar
Fruit
Inner gamboge disorder
4.05 0.15
0.10 0.00
0.28 0.01
1.08 0.02
1.16 0.04
0.10 0.00
5.1 0.1
T-test
Normal
2.32
0.46
0.67
1.63
1.17
0.17
6.2
0.08
0.02
0.04
0.02
0.03
0.00
0.23
**
**
**
**
ns
**
**
Data were expressed as mean ±SE; ns: no significance different by T-Test; **: significant difference 1%
by T-Test.
4.1.3 Ability to identify inner gamboge disorder fruits
Traders attained the highest ability to identify inner gamboge disorder
fruits (41.2%), the lowest were of customers (27.4%), ability to indentify
inner gamboge disorder fruits of orchards’ owners and sellers were 33.2 and
29.6%, respectively (Fig. 4.23). The diffrerences of the ability to identify
were mainly the time, traders identified fruit at harvest while other groups
identified when the peel has turned completely into dark purple; Fig. 4.24
showed that when obtained level-2 harvest index according to MOA (2002),
the peel of inner gamboge disorder fruits in small segment position often
changed color first.
Fig. 4.23 Ability to identify inner gamboge disorder fruits of traders, orchards’
owners, sellers and customer ( : ± SE)
12
Fig. 4.24 Characteristics of inner gamboge disorder fruits (A: exterior, B: inner)
Inner gamboge disorder ratio1
(%)
4.1.4 Relationship between plant age and the incidences of innder
gamboge disorder
Fig. 4.25 showed that the frequency of the inner gamboge disorder and
plant age had negative correlation at the significance level 1%. The
differences of inner gamboge disorder ratio and plant age were the growth,
the results in Tab. 4.4 showed the differences of physical-chemical
characteristics of mangosteen fruits from young trees (10 – 15 years) and old
trees ( > 50 years) at harvest.
50
a
40
30
r = 0,97**
b
bc
c
20
d
d
10
0
10 - 15 20 - 25 30 - 35 40 - 45 50 - 55
> 60
Plant age (year)
Fig. 4.25 Relationship between inner gamboge disorder ratio and plant age ( : ± SE)
Tab. 4.4 Physical –chemical characteristics of mangosteen fruit from young trees (10
– 15 years old) and old trees (> 50 years old) collected at Long Thoi commune –
Cho Lach district – Ben Tre province in 2012 crop season.
Item
Weight
Segment
Size
Quality
Fruit weight (g)
Total
Height (mm)
Width (mm)
CCCR
Peel thickness (mm)
o
Brix
Plant age
10 – 15 years
> 50 years
68.5±1.4
64.0±1.5
5.8±0.05
5.7±0.05
47.5±0.4
46.5±0.4
52.1±0.4
50.0±0.6
0.91±0.01
1.02±0.07
8.7±0.1
8.3±0.1
15.3±0.1
15.1±0.1
Different
*
ns
ns
**
ns
*
ns
Data were expressed as mean ±SE; ns: no significance different by T-Test; *: significant difference 5% by
T-Test;**: significant difference 1% by T-Test; CCCR: the ratio of fruit height/width
13
gamboge
Inner
bên trong1
bị xì mủdisorder
lệ trái
Tỷ
(%)
ratio(%)
4.2 Survey on factors causing inner gamboge disorder in mangosteen
fruits at harvest
4.2.1 Relationship between physical characteristics of fruits with
the incidences of inner gamboge disorder
4.2.1.1 Correlation of physical characteristics of fruit and the
incidences of inner gamboge disorder
Fig. 4.33 showed that there was a positive correlation between the
inner gamboge disorder ratio and peel thickness as harvest (r = 0.83**).
50
40
30
20
y = 8,3687x - 38,812
r = 0,83**
10
0
5,0
6,5
8,0
9,5
11,0
12,5
Peel
thickness
Độ dày
vỏ trái (mm)
(mm)
Fig. 4.33 Correlation of inner gamboge disorder ratio and peel thickness as harvesting
4.2.1.2 Effect of gibberellic and naphthalene acetic acid as foliar
spraying on the incidences of inner gamboge disorder at harvest
Spraying GA3 at concentration of 50 and 100 ppm had higher inner
gamboge disorder ratio from 2.42 – 2.47 folds than without spraying,
respectively (Tab. 4.6) because it increased peel thickness (Tab. 4.7) and
reduced pectin level in cell-wall of fruit-flesh (Tab. 4.9).
Tab. 4.6 Effect of the concentration of gibberellic and naphthalene acetic acid as
foliar spraying on inner gamboge disorder and translucent flesh disorder ratio (%) in
mangosteen trees aged 20 – 25 in Long Thoi commune – Cho Lach district – Ben
Tre province in 2012 crop season.
Treatments
0 ppm
GA3 25 ppm
GA3 50 ppm
GA3 100 ppm
NAA 25 ppm
NAA 50 ppm
NAA 100 ppm
F
CV (%)
Inner gamboge disorder ratio (%)
14.6b
13.2b
35.4a
36.1a
15.3b
12.5b
13.9b
**
20.1
Translucent flesh disorder ratio (%)
18.3
16.0
18.2
15.8
16.2
15.5
17.5
ns
20.8
14
Tab. 4.7 Effect of the concentration of gibberellic and naphthalene acetic acid as
foliar spraying on percentage of peel and edible weight (%), peel thickness (mm) in
mangosteen trees aged 20 – 25 years in Long Thoi commune – Cho Lach district –
Ben Tre province in 2012 crop season.
Treatments
0 ppm
GA3 25 ppm
GA3 50 ppm
GA3 100 ppm
NAA 25 ppm
NAA 50 ppm
NAA 100 ppm
F
CV (%)
Percentage of edible
weight (%)
29.4
26.7
26.9
29.7
28.7
29.9
30.8
ns
15.2
Percentage of peel weight
(%)
68.6b
70.7b
72.2b
79.8a
71.3b
69.3b
68.1b
**
7.2
Peel thickness
(mm)
7.4b
7.6b
7.7b
8.4a
7.7b
7.7b
7.6b
*
5.7
Tab. 4.9 Effect of the concentration of gibberellic and naphthalene acetic acid as
foliar spraying on the cell-wall composition of fruit-flesh in mangosteen trees aged
20 – 25 years in Long Thoi commune – Cho Lach district – Ben Tre province in
2012 crop season.
Treatments
0 ppm
GA3 25 ppm
GA3 50 ppm
GA3 100 ppm
NAA 25 ppm
NAA 50 ppm
NAA 100 ppm
F
CV (%)
Pectin (mg.g-1)
2.23a
1.93bc
1.96bc
1.80c
2.06ab
2.04ab
1.98bc
**
7.9
Hemicellulose (mg.g-1)
2.21
2.15
2.16
2.18
2.15
2.12
2.19
ns
4.4
Cellulose (mg.g-1)
4.05
4.15
4.20
4.35
3.90
3.80
3.85
ns
13.6
Means within a column followed by the same letter are not significantly different by Duncan test; ns: no
significant difference; *: significant difference 5%;**: significant difference 1%.
4.2.2 Survey on effect of soil moisture on the incidences of
gamboge disorder in fruits
4.2.2.1 Relationship between changes of soil moisture before
harvesting and the incidences of gamboge disorder
Slight increase or decrease of soil moisture had no effect on sudden
increase of inner gamboge disorder ratio, inner gamboge disorder ratio only
increased sharply when changes of soil moisture had a tendency to increase
quickly (Fig. 4.34).
15
Soil moisture
50
50
40
40
30
30
20
20
10
10
0
0
0
5
10
15
20
25
Soil moisture (%) 1
Inner gamboge
disorder ratio (%)
Inner gamboge disorder ratio
30
Period after the first harvest time (days)
Fig. 4.34 Changes of inner gamboge disorder ratio and soil moisture in 0 – 20 cm
depth upon harvest ( : ± SE)
4.2.2.2 Effect of timing of artificial water stress on the incidences of
inner gamboge disorder
Timing of artificial water stress in 2.5 months after completed
flowering increased inner gamboge disorder ratio from 9.8 – 11.2%
compared to other period at 1% significant difference (Tab. 4.11).
Chutinunthakun (2001) considered that fruits had gamboge disorder after
flowering 9 weeks earlier, Sdoodee and Chiarawipa (2005) also stated that
timing of water stress only increased inner gamboge disorder ratio in the
period of 9 weeks after flowering.
Tab. 4.11 Effect of timing of artificial water stress on the inner gamboge disorder
ratio and translucent flesh disorder ratio (%) in 23-year-old mangosteen trees in
Long Thoi commune – Cho Lach district – Ben Tre province in 2011 crop season
Timing of artificial water
stress
0.5 month after HNHT
1.5 months after HNHT
2.5 months after HNHT
When fruit had ”point”
F
CV (%)
Inner gamboge disorder ratio (%) Translucent flesh disorder ratio
(%)
15.2b
12.0
15.8b
11.5
26.4a
10.0
16.6b
8.75
**
ns
14.3
22.2
Means within a column followed by the same letter are not significantly different by LSD test; ns: no
significant difference; **: significant difference 1%; HNHT: completed flowering; ”point”: reached level-0
color index according to MOA standard (2002).
Timing of artificial water stress affected inner gamboge disorder ratio
because it affected sudden changes of soil moisture and water absorption of
latex, all period of water stress treament showed that sudden changes of soil
moisture (Fig. 4.35) and reduced dry mater content in latex (Tab. 4.15).
16
Sdoodee and Limpun-Udom (2002) considered that main causes of gamboge
disorder were sudden changes of water potential in soil and tree.
Soil moisture (%)
0,5 month
2,5 month
1,5 month
Fruit had “point”
35
31
27
23
19
15
NKHN
0.5
1.5
2.5
NKTH
Time after full flowering (month)
Fig. 4.35 Changes of soil moisture in 0 – 20 cm depth after completed flowering ( :
± SE, NKHN: beginning at flowering, NKTH: beginning at harvesting)
Tab. 4.15 Effect of timing of artificial water stress on dry mater content in latex (%)
according to the time in 23-year-old mangosteen trees in Long Thoi commune – Cho
Lach district – Ben Tre province in 2011 crop season
Period of water stress
treatment
0.5 month after HNHT
1.5 month after HNHT
2.5 months after HNHT
When fruit had ”point”
F
CV (%)
NKHN
33.2
34.0
33.9
31.9
ns
5.6
Solids content in latex (%)
0.5 month
1.5 month
2.5 month
29.0b
47.6a
70.9a
35.7a
40.8b
71.0a
35.3a
47.2a
56.9b
35.8a
46.5a
68.5a
**
**
**
6.0
3.9
3.2
NKTH
92.2
92.2
92.3
92.0
ns
2.4
Means within a column followed by the same letter are not significantly different by LSD test; ns: no
significant difference; **: significant difference 1%; HNHT: completed flowering; NKHN: when flower
fully opened; NKTH: beginning after harvesting; ”point”: reached level-0 color index according to MOA
standard (2002).
4.2.2.3 Effect of the number of artificial water stress times on the
incidences of inner gamboge disorder in fruit
Water stress once and twice had inner gamboge disorder ratio of 21.3
and 26.8%, increased 7.8 – 13.3% and water stress three times and four times
also increased when compared to the control of 20.8 – 24.8% (Tab. 4.17).
Aartificial water stress affected inner gamboge disorder ratio because it
affected sudden changes of soil moisture; the more water stress were
conducted, the higher changes of soil moisture increased (Fig. 4.37).
17
Tab. 4.17 Effect of the number of water stress treatment on inner gamboge disorder
and translucent flesh disorder ratio (%) in 24-year-old mangosteen trees in Long
Thoi commune – Cho Lach district – Ben Tre province in 2012 crop season
The number of artificial water
stress times (time)
0
1
2
3
4
F
CV (%)
Inner gamboge disorder ratio
(%)
13.5c
21.3b
26.8b
34.3a
38.3a
**
14.2
Translucent flesh disorder ratio
(%)
9.3c
11.5c
13.0c
17.5b
24.0a
**
16.5
Means within a column followed by the same letter are not significantly different by Duncan test; **:
significant difference 1%.
Control
Water stress once
Water stress 3 times
Water stress 4 times
Water stress twice
Soil moisture (%)
60
48
36
24
12
0
0
1
2
3
4
Period after artificial water stress (week)
Fig. 4.37 Changes of soil moisture in 0 – 20 cm depth after artificial water stress ( :
± SE)
4.2.3 Relationship between calcium content in soil and fruit and
inner gamboge disorder ratio
There was a negative correlation between inner gamboge disorder
ratio and exchangeable Ca2+ and total Ca2+ content in flesh at 1%
significance level (r = - 0.44** và - 0.52**) (Fig. 4.41 and 4.42). The
analysis results showed that total Ca2+ content in normal fruits was 1.29 folds
higher than inner gamboge disorder ones (Hình 4.43); Pechkeo et al. (2007a)
found that Ca2+ content in peel of normal fruits was higher than that of
gamboge disorder ones.
Inner gamboge disorder ratio1
(%)1
18
50
40
30
20
y = -2.9168x + 49.191
r = - 0.44**
10
0
3
4
5
6
7
8
Echangeable calcium content in flesh (meq.100g-1)
Inner gamboge disorder ratio1
(%)1
Fig.4.41 Correlation of the inner gamboge disorder ratio with exchangeable calcium
in soil
50
40
30
20
y = -0.3676x + 49.081
r = - 0.52**
10
0
20
30
40
50
60
70
-1
Total calcium content in flesh (mg.100g )
50
45
(mg.100g-1)
Total calcium content in flesh1
Fig. 4.42 Correlation between inner gamboge disorder ratio and total calcium
content in flesh
40
35
30
25
Normal
Inner gamboge disorder
Fig. 4.43 Total calcium content in flesh of normal fruit and inner gamboge disorder
fruit after harvesting ( : ± SE)
4.3 Study on preventing the incidences of inner gamboge disorder
in fruits and improving yield
4.3.1 Study on early flowering inducement
Flowering inducement after PBZ or KClO3 drenching for 1 and 2
months had lower inner gamboge disorder ratio from 5.3 and 4.4 folds when
inducing flowering in 3-month period lower 1.8 folds compared to the control
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