tóm tắt luận án khảo sát đặc tính không hột và đặc điểm hình thái thực vật của quýt Đường không hột ở đồng bằng sông cửu long (tiếng anh)

INTRODUCTION

* Thesis imperative task
Seedless citrus fruit was loving at home and abroad market.
Seedless or few seed sitrus fruit caused by threefold chromosome
mutation, by pollen or ovule sterity or by self-incompatibility
included the self-incompatibility caused by self-pollination
(Jackson and Futch, 1997; Jackson and Gmitter, 1997) [72] [71].
In the world, almost planted citrus variety was selected from
natural mutation and only small ratio was formed from cross
breeding program. In world market, many citrus varieties appeared
from natural mutation selection, such as Navel orange, Satsuma
mandarin…(Vu Cong Hau, 1996) [40] and few citrus pieces was
discovered in our nation such as Nam Roi pomelo, seedless Mat
orange (Tran Thi Oanh Yen et al., 2005) [35].
Sanh orange and Duong mandarin adjusted to Mekong Delta
condition. Plants gave high yield, delicious quality, and got good
price so that they were planted widely. However many seed in fruit
was the reason that reduced the using and selling of fresh fruit. Fruits
researches on Sanh orange and Duong mandarin noted that there had
been many seedless or few seed cases (less than 5 seed per fruit).
Hence, Can Tho university co-operated with Vinh Long Science and
Technology Deparment for finding and studying seedless Sanh
orange and Duong mandarin in Mekong delta. That subject had the
result that two seedless Duong mandarin were discovered from
Duong mandarin population in Tan Phuoc commune, Lai Vung town,
Dong Thap province (Nguyen Bao Ve et al., 2007) [13].
Thus, subject “Study of seedless characteristic and morphology
characteristics of seedless duong mandarin in the Mekong Delta” was
carried out for having basic to develope the new seedless Duong
mandarin in Mekong delta

2
* Thesis research target
(i) study identification characteristics and relationship of the
two seedless Duong mandarin plants to each other and with the
normal seedy Duong mandarin plant;
(ii) define cause for seedless character of seedless Duong
mandarin plants;
(iii) evaluate the stability of the seedless characteristic
through the croping time, in three cultural regions of Mekong Delta,
in three grafting generations and on different rootstocks;
(iv) study fruit yield potential and quality of the seedless
Duong mandarin in Mekong Delta.
* The new of thesis
It researched on new materials, the two seedless Duong
mandarin plants discovered among seedy Duong mandarin
population in Mekong Delta.
The “late development” characteristic of ovules resulted for
producing completely seedless Duong mandarin fruits. It was the
characteristic helped to shape seedless Duong mandarin that was
found firstly in Viet Nam.
The two seedless Duong mandarin plants could be indentified
by the RAPD technique (Random amplified polymorphic DNA) with
the aid of DNA markers.
* Contribution of thesis
+ Science signification
Providing fairly completed information about two seedless
Duong mandarin which were discovered in the Mekong Delta. The
morphology characteristics of tree such as branches, leaves, flowers

and fruits of the two seedless Duong mandarin plants were
homogeneous and not different to the seedy Duong mandarin plant. It
was able to identify the two seedless Duong mandarin plants by
RAPD technique with the aid of DNA markers. There was the
proximity close relationship between the two seedless Duong
mandarin plants and they were closed to the normal seedy Duong
3
mandarin plant; The cause of producing completely seedless fruits on
these two seedless Duong mandarin plants was the “late
development” of ovule; The seedlessness characteristic of the two
seedless Duong mandarin plants was stable through croping time, in
intercrop condition and due to cross pollination with other species of
citrus, at three different cultural regions in Mekong Delta, in three
grafting generations and on three kinds of rootstocks (Mat orange,
Tau lime and Hanh); These seedless Duong mandarin varieties gave
good fruit yield and quality in Mekong Delta.
+ Reality significant
In 5 years, research results helped to determine the stability of
seedless characteristic of the two seedless Duong mandarin fast, other
characteristics are basically not different to normal seedy Duong
mandarin. They are valuable scientific basises for the early
development of these precious varieties in widely production.
* Main object and range of thesis
+ Main object of thesis are two seedless Duong mandarin were
discovered in the Mekong Delta.
+ Range of thesis:
- Observate on the mother plant and progeny scion grafting plants.
- Three different cultural regions (Dong Thap, Can Tho, Vinh
Long) in Mekong Delta.
- In the period from 2007 to 2011.

- Observation of plant morphological characteristics and genetic
relationships used RAPD technique, pollen and ovule characteristics,
the stability of seedless characteristic (through croping time, in three
different cultural regions, in three grafting generations and the three
kind of rootstocks (Mat orange, Tau Lime and Hanh), growth, yield
potential and fruit quality of seedless Duong mandarin.
* Thesis structure
This thesis is 131-page thick, consisted four chapters with 35
tables, 34 figures and 3 appendices. There were 152 reference
document.
4
CHAPTER 1
LITERATURE OVERVIEW
1.1 DUONG MANDARIN OVERVIEW
Nguyen Bao Ve and Le Thanh Phong (2004) [12] suggested
that Duong mandarin is belong to the Citrus genus, Eucitrus
subgroup, Rutaceae family and Aurantioideae subfamily.
In Mekong Delta, Duong mandarin was one of popular
mandarin variety had good quality. The total Duong mandarin
cultivate region was about 9640 hectares, accounting for 20 - 30% of
the citrus fruit regions, focusly cultivate at Lai Vung - Dong Thap,
Phung Hiep - Hau Giang, Tra On - Vinh Long, Cai Be - Tien Giang,
Cang Long - Tra Vinh and scattered in some provinces (Do Minh
Hien, 2008) [2].
1.2 MOPHOLOGY CHARACTERISTIC OF DUONG MANDARIN
In 5 years old, Duong mandarin plants had an average of 4.1 m
height (Tran Thuong Tuan et al., 1999) [38]. According to Tran The
Tuc et al. (1998) [32] and Duong Hong Dat (2003) [4], plants have
thin canopy, acrodome and many secondary branches, canopy
diameter is 2.5 m.

Tran Thuong Tuan et al. (1999) [38] indicated that Duong
mandarin had simple leaf devision, evergreen, its color was green
with mark shape. According to Pham Hoang Ho (2003) [22], Duong
mandarin leaf have stalk but petiole is absent, leaf blade had many
conspicuous oil sacks. Its leaves often have chopped tip (Duong
Hong Dat, 2000 [3]
Citrus blossom was single or clusters, grew from axillary, be
usually bisexual flowers (Tran Thuong Tuan et al., 1994; Nguyen
Bao Ve and Le Thanh Phong, 2004; Tran Van Hau, 2009) [37]12]
[39]. Full bloom have 1.3 - 1.5 cm petal length, with 5 sepals. Five
white thick petals is alternate with the others and with the sepals.
According to Pham Hoang Ho (2003) [22], Duong mandarin
fruit had from round to slightly flattened shape, with knob at bottom
and thin peel. Duong mandarin fruits has a bright yellow and smooth
5
in ripeness stage. Each fruit had average of 10.7 sections, easily
separated and peeled by hand.
1.3 CITRUS POLLEN AND OVULE CHARACTERISTIC
Pollen have outer wall which consisted of two membrane
layers: the outer membrane and the inter membrane. According to Ha
Thi Le Anh (2005), [5], inside the wall, there are cytoplasm and two
nucleus: the big round somatic nucleus, which will germinate to
produce pollen tubes and smaller oval reproductive nucleus, which
will became two sperm.
Spiegel-Roy and Goldschmidt (1996) [125] considered that the
ovule of citrus have contrary attached format that the hole opposite to
the axis of the ovary. Matured ovule including embryonic stem,
embryo sac with eight cores and two ovule sheath. According to
Jackson and Gmitter (1997) [71], the sooner or later mature
(maturity, ripeness) depend on variety characteristic. This feature can

be affected by inter and outster factors.
1.4 POLLINATION AND FERTILIZATION OF CITRUS
The pollen is brought to stigma of the same flower or other
flowers by wind or insects, it called pollination. The molecules
forming the pollen surface interactions with protein and
polysaccharide on stigmas. If they are compatible, the pollen will be
affected to germinate. Pollen tubes germinate and penetrate into the
embryo sac inside the ovule.
According to Phan Kim Ngoc and Ho Huynh Thuy Duong
(2000) [25], fertilization is the result of the fusion of a sperm and an
embryo. Fertilization occurs after pollination. When the pollen tube
enters the ovule hole, two sperm cells came out through the ovule
holes, two cells escape through a hole in the wall of the pollen tube: a
sperm mix with the egg, forming a diploid nucleus; the other
penetrate into the large central cell contains two polar nucleus, all
three of them combine together to create triploid nucleus, triploid cell
develope to be endosperm, first source of nutrients for seedling.
Whole of this phenomenon is called the double fertilization (Spiegel-
Roy and Goldschmidt, 1996) [125].
6
1.5 SEEDLESS CHARACTERISTIC OF CITRUS
Seedless characteristic is the precious characteristic not only for
all kinds of fruit but also Citrus because it was the requirement of the
fresh fruit market and even the processing juice industry. Seedless
characteristic of citrus has many dominant factors and was influenced
by environmental conditions. Forming seedless fruit can or can not be
completed, that mean it can have absolutely no seeds or the number
of seeds were reduced .
Autonomic parthenocarpus is a phenomenon that form seedless
fruit without pollination, thus fertilization occurs without external

stimulation (Spiegel-Roy and Goldschmidt, 1996)[125]. On citrus,
strong sterity combined with Autonomic parthenocarpus to become
the necessary condition for production seedless fruit (Ollitrault et al.
2007) [101]. Eventhough sterity is capable, seedless fruit can not be
produced because of incapable autonomic parthenocarpus. Ollitrault
et al. (2007) [101] considered that the Autonomic parthenocarpus,
caused seedlessness without pollination, was a key process in citrus.
According Ollitrault et al. (2007) [101], several varieties of male
sterility and self-incompatibility can not form seedless fruit because
autonomic parthenocarpus was absent. Therefore, the autonomic
parthenocarpus ability are indispensable characteristics for the
production of seedless fruits and this seem to be popular on citrus.
Mooney (1997) [89] found that triploid Citrus have great
commercial potential because of the high degree of seedless, but the
frequency of triploid plants were very low in the wild. Reed (2003)
[113] thought that self-incompatibility is the disfunction of the male
and female gametes to form seeds when self-pollinated occurs, the
mismatch of the male gametes on the same species stigmas, or
prevent the growth of the pollen in the same species styles. The self-
incompatibility will create seedless fruit when they were not planted
with the other spieces.
Self male sterility can result from abnormal development of the
stamens leaded to deficiencies in the pollen development process.
Tran Thuong Tuan (1992), [36] indicated that unviable male gametes
caused of the male sterility. Female sterility is a very important trait
7
which closely related to the seedlesss characteristics and heritability
(Yamamoto et al., 1995; Yamamoto et al., 2001) [149] [148].

CHAPTER 2

MATERIAL, CONTENT AND RESEARCH METHOD
2.1 CONTENT AND RESEARCH METHOD
Including 4 part, with 8 observations and 5 experiments:
2.1.1 Study of mophology characteristic and genetic relationship
Consists of two observations in morphological characteristics
and use of RAPD technique to identify and determine the relationship
of the two seedless Duong mandarin which had been discovered in
the Mekong Delta.
2.1.2 Study of pollen and ovule of seedless Duong mandarin
There are 2 pollen observations and 3 ovule observations for
finding out the characteristics of pollen and ovule that were related to
the seedless characteristics.
2.1.3 Evaluate the stability od seedless characteristic
Includes an observation and five experiments to evaluate the
stability of seedless characteristic through croping time, on 3
cultivation regions in the Mekong Delta, in 3 grafting generation and
on different rootstocks.
2.1.4 Evaluate yield potential and fruit quality of seedless Duong
mandarin
Evaluate the growth ability, yield potential and fruit quality in
scion grafting plants with Mat orange rootstock in Lai Vung district,
Dong Thap province, where is one of the typical mandarin cultivate
region in Mekong Delta.
2.2 REGIONS, MATERIAL AND RESEARCH PERIOD
The study was carried out in Dong Thap, Can Tho and Vinh
Long. Main material are seedless Duong mandarin No. 1 (code 1),
seedless Duong mandarin No. 2 (code 80) and normal seedy Duong
mandarin as controls (code 63) (Nguyen Bao Ve et al., 2007) [13].
The research period is from 2007 to 2011.
8

CHAPTER 3
RESULTS AND DISCUSSIONS
3.1 MOPHOLOGY CHARACTERISTIC AND GENETIC
RELATIONSHIP OF SEEDLESS DUONG MANDARIN
The results showed that canopy got elliptical shaped, vertical
posture, branch density were sparse, scion direction and branching
devision much, sparse spine density, spine is straight and short,
smooth tree-trunk and angle of branching were moderate. In general,
the mophology characteristics of the two seedless Duong mandarin
were same to normal seedy Duong mandarin.
Leaf morphological characteristics between the two seedless
Duong mandarin is same to each other and not different with seedy
Duong mandarin. The flowers characteristics of two seedless Duong
mandarin are the same and similar to seedy mandarin. Time from the
onset of bud to the blooming of the two seedless Duong mandarin is
about 11 - 12 days, from blooming to stigma fall is about 2 - 3 days,
the same to normal seedy Duong, mandarin (control). These shows
that development period and capable blooming period for receiving
pollen in two seedless Duong mandarin is normal, and not different
to seedy Duong mandarin (control). The flower development of
seedless Duong mandarin No. 1 is same with seedless Duong
mandarin No. 2 and be same to seedy Duong mandarin(control)
Fruits of two seedless Duong mandarin and fruits of seedy
Duong mandarin have the same shape. They are big circular and
rather flat. Bottom of fruit have knob, top of fruit got slightly
concave. Peel transfer to smooth yellow Green when ripe. Basically,
the morphological characteristics between the two seedless Duong
mandarin are same, and not different to seedy Duong mandarin
(completely seedless characteristic).
In short, except the completely seedless characteristic,

morphological characteristics such as stems, leaves, flowers and
fruits are the same between the two seedless Duong mandarin and
seedy Duong mandarin (control).

9




Figure 3.4 Seedless Duong mandarin fruit Shape
Due to analyzing results, all 7 used primer steady brought
useful magnification products with the aid of RAPD technique. Using
RAPD technique with seven primers used, a total of 46 tape recorded.
Including nine tapes appear polymorphisms in the primer SO15 (1),
SN20 (4 tape), SN06 (2 tape) and A13 (2). SO15 and A13 primers
can distinguish two seedless Duong mandarin with seedy Duong
mandarin. By using primers A13, seedy Duong mandarin had the
amplification of DNA at two positions 650 bp and 750 bp (noted a
and b on figure 3.5), while the two seedlesss Duong mandarin do not
give amplification products in this location. Meanwhile, the prey
SN06 and SN20 can distinguish two seedless Duong mandarin to
each other and with the seedy Duong mandarin (to distinguish the
three plants together).



Seedless No. 1 Seedless No. 2 Seedy (control)


Up side

Downside

Cross side

10










Figure 3.5 Seedless Duong mandarin PCR record with A13 primer
M: standard meter 1 kb; 1: seedless Duong mandarin No.1; 2: seedless
Duong mandarin No.2; 3: seedy Duong mandarin (control).
Figure 3.8 shows two seedless Duong mandarin and seedy
Duong mandarin as control fusion to be a main branch. It included
seedy Duong mandarin, seedless Duong mandarin No. 1 and seedless
Duong mandarin No. 2 with the high coefficient (0.87). Two seedless
Duong mandarin constitute a secondary branch and they have the
same coefficient (0.92). Thus, the two seedless Duong mandarin had
the close genetic relationship to each other and they have the close
genetic relationship to seedy Duong mandarin.

Figure 3.8 Branch diagram of seedless Duong mandarin
1: seedless Duong mandarin No. 1; 2: seedless Duong mandarin No. 2;

3: seedy Duong mandarin (control)).
In summary, the morphological characteristics of two seedless
Duong mandarin are basically same about trunk, branches, leaves,
0,
87

0,92


M 1 2 3

a
b
1.000

500

650

850

11
flowers and fruits and not different seedy Duong mandarin
(excluding completely seedless characteristic). It was able to identify
two seedless Duong mandarin by RAPD technique with DNA
markers aid. Beside, the genetic relationships analysing result
showing two seedless Duong mandarin have close relationships to
each other and close to the commercial seedy Duong mandarin in the
region.
3.2 POLLEN AND OVULE CHARACTERISTIC OF TWO

SEEDLESS DUONG MANDARIN
3.2.1 Pollen characteristic
Observations results showed that the pollen germination and
pollen tube length of the seedless Duong mandarin No. 1 and
seedless Duong mandarin No. 2 seed were not significant different to
seedy Duong mandarin (control). Force pollination results also
showed that using natural pollen of seedless Duong mandarin No. 1
and No. 2 in seedy Duong mandarin, the number of full seeds/ fruit,
flat seeds/ fruit were no significant differences to each other and to
seedy Duong mandarin (control). It showed that pollen of seedless
Duong mandarin were unsterile. Thus, seedless characteristics of the
two seedless Duong mandarin is not caused by pollen.
3.2.2 Ovule characteristic
3.2.2.1 Ovule Developement
* Before full bloom stage
In seedy Duong mandarin, ovule appeared early and their
quantity was stable on 5 flower stage (from 10.4 to 10.8 ovule). In
contrary, there are completely no ovule in seedless Duong mandarin
No. 1 and No.2 till full bloom stage. Late development characteristic
in full bloom stage may help to form seedless fruit in seedless Duong
mandarin No.1 and No.2
Table 3.18 and Table 3.19 show that in small flowers (flower
diameter is 3.5 mm), the ovule size of seedy Duong mandarin was
quite large (203 µm length and 130 µm width) and rapidly developed
in 5 mm. from this moment till the full bloom stage, the ovule size of
seedy Duong mandarin virtually unchanged (396 - 404 µm length and
12
246 - 258 µm width). At this time, the ovule had the pear shape
(Figure 3.14).
The stability of the size of the ovule in the period before and on

flowering time allows to infer that ovule was mature (ripe) and may
be ready for fertilization. Ovule growth characteristics on flowering
time is a common feature of crops, because it is the best time for
pollination, fertilization. This feature has helped commercial seedy
Duong mandarin to have normal seeds. Thus, in the cross-sectional
area of the ovary surgery of seedless Duong mandarin, mature ovule
is pear-shaped and about the size of 404 ± 21 µm x 258 ± 23 µm.

Table 3.18 Ovule width (µm) at different flower size of seedless
Duong mandarin
Flower size (diameter, mm)
3,5 4,0 4,5 5,0
Bloo
m
Mandarin tree
X

Sd

X

Sd

X

Sd

X

Sd

X

Sd

Seedless No.1 0 - 0 - 0 - 0 - 0 -
Seedless No.2 0 - 0 - 0 - 0 - 0 -
Seedy (control) 203

20

279

28

331

48

396

35

404

21

X
: average; Sd: standard deviation;

Table 3.19 Ovule width (µm) at different flower size of seedless
Duong mandarin
Flower size (diameter, mm)
3,5 4,0 4,5 5,0
Bloom
Mandarin tree
X

Sd
X

Sd
X

Sd
X

Sd
X

Sd

Seedless No.1 0 - 0 - 0 - 0 - 0 -
Seedless No.2 0 - 0 - 0 - 0 - 0 -
Seedy (control) 130

17 202 32 222

27 246 17 258

23
X
: average value; Sd: standard deviation;
13






Figure 3.14 Ovary Cross slices before blooming of seedless Duong
mandarin; zoom 100 time.
Flower
with
4 mm
diameter

Flower
with
4.5 mm
diameter

Flower
with
5 mm
diameter
Blooming
Seedless No. 1 Seedless No. 2 Seedy (control)
Flower
with

3.5 mm
diameter

100 µm
14
* After blooming stage
On seedy Duong mandarin, number of ovule remained stable at
3 flower size after bloom (11.0 - 11.3 ovule). Ovule of two seedless
Duong mandarin appeared similarly and later than seedy Duong
mandarin ovules. Till the petal fall stage, it recored that ovule
appeared, but the number of ovule of seedless Duong mandarin is
less than the number of ovule seedy Duong mandarin (2.4-4.5 ovule).




Figure 3.15 Cross slice of ovary after blooming of seedless
Duong mandarin; zoom 100 time.
Seedless Duong mandarin ovule have unchange width (in the
range of 266 - 270 µm), the length of ovule developed followed
Petal

fall
Stigma

fall
Fruit

At
2.5mm

diameter
100 µm
Seedless No.
1

Seedless No.
2



Seedy (control)

15
flower side (petal fall: 411 µm, stigma fall: 443 µm, fruit sixe at 2.5
mm: 470 µm). The change of this size may be due to the process of
developing seeds after the fertilized. Meanwhile, in two seedless
Duong mandarin there are few ovules appear, but the size is smaller,
petal fall had the range of 77-81μm length and in the range of 63 - 66
µm width, in stigma fall, the length is in the range of 127 - 131 µm
and at fruit size 2.5 mm had length in 191 - 199 µm. The results
showed that, in seedless Duong mandarin No. 1 and No. 2, till 2.5
mm diameter fruit, ovule is still developing, has not yet reached
mature size. So maybe, ovule of two seedless Duong mandarin still
immature at this time.
In summary, the ovule of two seedless Duong mandarin had the
same "late development" characteristics to the ovule of seedy Duong
mandarin. May be the ovule characteristics "late development" is
cause for seedless fruit is seedless Duong mandarin.
3.2.2.2 Pollent tube appearance in ovary
* Self pollination condition

In self-pollination condition, in all parts of the female structure
(stigma, above styles, below styles and ovary) at 3 days after
pollination of the three plants, the observation reported the presence
of pollen tubes (Figure 3.16). The observation results also
demonstrated for ovule characteristics of seedy Duong mandarin had
grown in the blooming stage because of the fertilization occurence
(pollen tube came through the hole in the ovule and came to embryo
sac) . Meanwhile, in seedless Duong mandarin No. 1 and No. 2,
pollination still occurs, pollen tubes reach to the ovary, but ovule is
immature at this time so fertilization can not occur so that it can not
create seeds. It also confirmed the late development characteristics of
two seedless Duong mandarin(Figure 3.16).
16





Figure 3.16 Slice of female tructure of flower on 3 days after sefl
pollination of seedless Duong mandarin; zoom 100 times;
white narrow direct the pollen tube.
* Open pollination condition
The two seedless Duong mandarin and seedy Duong mandarin
on 3 days afer pollination, with 3 types of pollination (self
pollination, pollinate with seedy Duong mandarin pollen and
100 µm
Stigma


Above

styles
Below
styles
Ovary


Seedless No. 1 Seedless No. 2 Seedy (control)
17
pollinate with Mat orange pollen), most parts of the female structure
(stigma, above styles, below styles and ovary) were recorded that
there were the presence of pollen tubes (93.3 to 100%), difference
was not significant by χ2 testing.
3.2.2.3 Ovule fertilization bability
Seedless Duong mandarin No. 1 and No. 2 had fruits with
absolutely no-pollinated seeds in 3 types of pollination. Meanwhile,
the seedy Duong mandarin with 3 types of pollination have the
formation of seeds, number of full seeds/fruit was in range of 9.07 to
11.53 and the number of immature seeds/ fruit was 1.93 to 2.03
3.2.3 Discussion about seedless Cause
Flowering stage is the best time for pollination, fertilization and
forming seed. At this time, in the seedy Duong mandarin, through
morphological anatomy cross-sectional ovary, most ovule is mature,
perhaps due to this characteristic made famous commercial Duong
mandarin in the Mekong Delta has many seeds. Meanwhile, ovule of
two seedless Duong mandarin were still immature. By the petal fall
stage (about 2 - 3 days after blooming), the ovule of two seedless
Duong mandarim appeared, but they got small size and far from
mature size. So, whether pollination at this time (very difficult to
occurs due to petal fall, dried stigma, color changed and no longer to
receive pollen anymore), then fertilization is difficult to implement

due to ovule is not mature. The "late development" characteristic was
not in sync with other progression of the flower is the cause of
seedlessness of the two seedless Duong mandarin. Characteristics
that ovule will be mature for few days later than the time of blooming
was recorded on Washington Navel oranges and Satsuma tangerine
(Jackson and Gmitter, 1997) [71], is the world's seedless citrus.
Although possible pollination process but fertilization can not occurs
because there is no mature ovule, so that it form the seedless fruit.
In summary, two seedless Duong mandarin pollen were
unsterile, They are capable to germinate, fertilize and form seeds as
seedy Duong mandarin, hence two seedless Duong mandarin pollen
were not related to seedlessness. Seedlessness characteristic of two
seedless Duong mandarin is not related to self-incompatibility
18
because pollen tubes was still present in the ovary itself and totlaly
seedless when cross-pollinated with other citrus (Duong mandarin
seeds, Sanh orange). "Late development" characteristic caused
seedlessness of seedless Duong mandarin No. 1 and No. 2 .
3.3 STABILITY OF SEEDLESSNESS CHARACTERISTIC
3.3.1 Stability of seedlessness through croping time
The results showed that all fruits in the 5-year observation from
7 years old until 11 years old, the trees have absolutely seedless fruits
(no mature seeds and no immature seeds) in intercrop conditions with
other citrus (Duong mandarin, Tieu mandarins, Tau lime, Mat
orange, Sanh orange). Completely seedlessness characteristic of the
two seedless Duong mandarinare stable through croping time in
intercropped condition with other citrus varieties.
3.3.2 Stability of seedlessness in different cultivation regions
Results indicated that there are no presence of ovule in most
ovary at the flowering time in seedless Duong mandarin No. 1 and

No. 2 in all 3 experiments regions (Dong Thap, Can Tho, Vinh
Long). At the time of 3 days after blooming (petal fall), in all 3
experiments regions, the ovule in seedless Duong mandarin No. 1
and No. 2 ovules developed more than blooming stage, but there are
few ovule with small size.
All harvest fruits were completely seedless . Meanwhile, the
seedy Duong mandarin in three point Lai Vung - Dong Thap, Can
Tho city and Tra On Vinh Long sequential of full seed/ fruit is 8.56,
10.26 and 12.22; and immature seeds / fruit was 2.33, 2.08 and 2.36.
In short, absolutely seedlessness characteristics of two seedless
Duong mandarin may have genetic ability and maintain stable in
clonal generations (on Mat orange rootstock) in 3 cultivation regions
(Dong Thap, Can Tho and Vinh Long) of Mekong Delta.
3.3.3 Stability of seedlessness in grafting generations
Ovary observation results showed that do not have the presence
of the ovule at the blooming stage. At three days after blooming stage
there are no ovule with the mature ovule morphology and size
(ripening). Two seedless Duong mandarin through three generations
1 a 1 b
19
on Mat rootstock gave absolutely no seeds in the fruit of all
treatments.
In short, absolutely seedlessness characteristics of seedless
Duong mandarin No. 1 and No. 2 have the genetic ability and
maintain stability in the three grafting generations on Mat orange
rootstock.
3.3.4 Stability of seedlessness on different rootstock
At the blooming stage and 3 days after blooming stage, threr are
no ovule with mature ovule morphology and size in all treatments.
Full seeds in all treatments was 0.00. Immature seeds also have

similar results (0.00). This is approriate with the recorded that ovule
at the blooming stage and 3 days after blooming stage. The late
development characteristics of ovule remain stable at seedless Duong
mandarin on different rootstock.
Thus, seedlessness characteristics of seedless Duong mandarin
remain stable in the next generation by asexual multiplication on
different rootstock (Mat orange, Tau lime and Hanh) (Figure 3.26).
3.3.5 Seedlessness characteristic stability disscussion
Results of ovule presence recorded from the experiments
showed that late development characteristics of seedless Duong
mandarin No. 1 and No. 2 ovules were maintained when they had
grown in three cultivation regions in the Mekong Delta, on three
grafting generations and on 3 kinds of rootstock (Mat orange, Tau
lime and Hanh). Thus, the Late development characteristic of ovules
depends largely on the variety property. According to Jackson and
Gmitter (1997) [71] maturity characteristics of the ovule occurs
sooner or later will depends mainly on seeds, Foster grapefruit ovule
are mature on few days before the blooming stage, Pineapple Orange
ovule are mature right on blooming stage and Washington Navel
orange and Satsuma mandarin ovule are mature few days after
blooming stage (these are 2 famous seedless citrus in the world).
Due to late development characteristics of ovule may have
genetic ability, that helped the seedlessness characteristics stability of
two seedless Duong mandarin discovered in Mekong Delta in high
20
degree. The absolutely seedlessness characteristic remained stable
through croping time, in intercropped with other citrus; in three
cultivation regions of Mekong Delta; on 3 grafting generations, and
on 3 different rootstocks (Mat orange, Tau lime and Hanh). This
result allows to propagate rapidly seedless Duong mandarin No. 1

and No.2 by grafting on 3 types of rootstock (Mat orange, Tau lime
and Hanh), planted in regions that had comfortable condition for
growing citrus in Mekong Delta and especially can be intercropped
with other citrus that absolutely seedlessness characteristic remained
stable.
However, accordiing to Jackson and Gmitter (1997) [71]
sooner or later maturity characteristics of the ovule can be affected by
a number of agents inside and outside. So, there may be some factors
that make the development of seedless Duong mandarin No. 1 and 2
ovule mature earlier and the time that stigmas receive pollen will be
longer (the period from blooming to petal fall for about 2 - 3 days in
seedless Duong mandarin), then this time can occur fertilization and
formation of seeds in seedless Duong mandarin. This issue should be
studied further.
3.4 YIELD POTENTIAL AND FRUIT QUALITY OF SEEDLESS
DUONG MANDARIN
3.4.1 Growing of tree
Diameter of rootstock, scion diameter, the ratio of rootstock
diameter and scion diameter, plant height, canopy width through
croping time showed that there are no difference between three
treatments. Therefore, the growth of seedless Duong mandarin No. 1
No. 2 seed is not equivalent to each other and do not different with
seedy Duong mandarin which were grown popular in the Mekong
Delta.
3.4.2 Yield
Percentage of fruit set can be used to evaluate the yield
potential of seedless Duong mandarin No. 1 and No. 2. Table 3.32
shows the percentage of fruit set of three treatments with the general
decreasing trend in the period from 30 - 90 days after flowering, but
21

there is no significant difference between the three treatments about
fruit set rate in each stage through statistical analysis. Thus, the fruit
set ability of seedless Duong mandarin No.1 and No.2 are equivalent
to each other and no significant difference to seedy Duong mandarin.
Table 3.32 Percentage of fruit set (%) from blooming stage to 90
days after blooming stage of seedless Duong mandarin
Day after blooming Treatment
(Duong mandarin)
30 45 60 75 90
Seedless No. 1 24,3 22,4 20,9 20,3 18,9
Seedless No. 2 25,4 23,5 22,4 20,8 19,3
Seedy (control) 26,0 24,4 23,3 21,6 20,5
F ns ns ns ns ns
CV (%) 66,8 70,2 86,0 74,1 73,7
The figures were transferred to arcsin√x for statistical analyzationi, those
zero value were transferred to 1/4n before transferred to arcsin√x; ns: not
significant.
Total number of fruit on tree is not statistically significantly
different between seedless Duong mandarin No. 1 and No. 2, and
with seedy Duong mandarin (control). Fruit weight of seedless
Duong mandarin No. 1 (98.9 g) and seedless Duong mandarin No. 2
(88.0 g) had lower tend than the seedy Duong mandarin (117.2 g),
but by the analysis statistics, this difference is not significant. Due to
yield ranged from 11.3 - 20.5 kg per tree, the statistical analysing
showed that there is significant difference among treatments. the
productivity of seedless Duong mandarin No. 2 (11.3 kg / plant) was
lower than seedy Duong mandarin (20.5 kg / tree), and equivalent to
seedless Duong mandarin No. 1 (15 kg / tree). Meanwhile, the yield
of seedless Duong mandarin No. 1 is not significantly different with
seedy Duong mandarin. In generally, the yield of seedless Duong

mandarin tend to be lower than the seedy Duong mandarin (control).



22
Table 3.33 Total fruit per tree, fruit weight and Yield of seedless
Duong mandarin
Treatment
(Duong mandarin)
Total fruit

per tree
Fruit
weight (g)
Yield
(kg/tree)
Seedless No. 1

157

98,9

15,0 ab

Seedless No. 2 131 88,0 11,3 b
Seedy (control) 177 117,2 20,5 a
F

ns

ns

*

CV (%) 45,5 18,7 39,5
ns: not significant; *: different at significant level of 5%.
The rate of fruit set, number of fruits per tree and fruit weight
are not significantly different between treatments, but seedless Duong
mandarin No. 1 and No. 2 tend to be lower than the seedy Duong
mandarin (control) and the coefficient of variation (CV) is quite high.
This caused by not only the reason that young plants have productive
behavior is not stable, but also the autonomic parthenocarpus is not
stable. According to Purdure University (2005) [108], there are three
levels of autonomic parthenocarpus: weak, medium and strong. That
affect the ability of fruit set. So the study of seedless Duong
mandarin autonomic parthenocarpus should be continue to have
appropriate cultivate practices. Beside, the study of appropriate
cultivate practices is nescessary for a new variety, especially for
seedless variety, in order to promote the variety potential well.
Although the productivity of seedless Duong mandarin tend to
be lower than seedy Duong mandarin, the yield of 11.3 - 15 tonnes /
ha (planting at density of 1,000 trees / ha, with a distance of 3 x 3.5
m) may still be acceptable in production due to the valuable
seedlessness characteristic. Also, by this time tree is young, canopy
diameter at blooming period (about 21 months after planting) is only
about 2 m. Hence, it is able to infer that their product will be
improved higher at fully stably developed age than this time (The two
mother plants have 20 - 23 kg / tree). With these results and the
above discussion shows that seedless Duong mandarin No. 1 and 2
will have good yield potential with suitable conditions for planting

citrus in the Mekong Delta.
23
3.4.3 Fruit quality
Flesh of seedless Duong mandarin No. 1 and No.2 and flesh of
seedy Duong mandarin have color of orange, fruit flesh color is same
to each other (Figure 3.32). Fruit core is quite vesicle, fruit juice is
very sweet and fragrant.
Figure 3.32 Cross slice of seedless Duong mandarin
Brix degree of them are in range of 9.24-9.47%, pH is in range
of 4.70-4.88 and quantity of vitamin C is in range of 35.2-36.5
mg/100g. They all are not significantly different among 3 treatments.
Due to those results showed that fruit quality of seedless Duong
mandarin No.1 and No.2 are not different with seedy Duong
mandarin fruit quality.
In short, the growth of seedless Duong mandarin No. 1 and
No. 2 are normal, equivalent tantamount to seedy Duong mandarin.
Both seedless Duong mandarin No. 1 and seedless Duong mandarin
No. 2 have delicious fruit quality, equivalent to each other and not
different to seedy Duong mandarin, which is famously fragrant,
delicious and sweet in the Mekong Delta, more specially that they are
seedless. Although the yield of seedless Duong mandarin lightly
lower than seedy Duong mandarin, seedless Duong mandarin have
the development potential in suitable citrus growing conditions
regions of Mekong Delta with the good yield potential and quality.
CHAPTER 4
CONCLUSION AND SUGGESTION
4.1 CONCLUSION
- The morphology characteristics such as branches, leaves,
flowers and fruits of the two seedless Duong mandarin plants were
homogeneous and not different to the seedy Duong mandarin plant. It

Seedless Duong mandarin No. 1
Seedless Duong mand
arin No. 2

2

Seedy Duong mandarin (control)

24
was able to identify the two seedless Duong mandarin plants by
RAPD technique with the aid of DNA markers. There was the
proximity close relationship between the two seedless Duong
mandarin plants and they were closed to the normal seedy Duong
mandarin plant.
- The cause of producing completely seedless fruits on these two
seedless Duong mandarin plants was the “late development” of ovule
- The seedlessness characteristic of the two seedless Duong
mandarin plants was stable through croping time, in intercrop
condition and due to cross pollination with other species of citrus, at
three different cultural regions in Mekong Delta, in three grafting
generations and on three kinds of rootstocks (Mat orange, Tau lime
and Hanh)
- These seedless Duong mandarin varieties gave good fruit yield
and quality in Mekong Delta.
4.2 SUGGESTION
- Studying continuously about yield and fruit quality of seedless
Duong mandarin at three different cultural regions, on kinds of
rootstocks,… Build up the “head variety” orchard and surveying
large scale of the seedless Duong mandarin plants in suitable growing
conditions areas, according to the process of new variety acceptance,

aimed to produce varieties and develope widely cultivation in
Mekong Delta.
- Researching and evaluating the level of parthenocarpy character
of seedless Duong mandarin. Concurrently, it is essential to research
approriate cultivation techniques for seedless Duong mandarin
production.
- Understanding more factors (plant hormones, nutrients,…)
have affected on stability of completely seedless characteristic of
seedless Duong mandarin fruit.
- In following researchs, finding out hereditary characteristics
of seedless Duong mandarin, it’s able to use SSR (Simple Sequence
Repeat) and SCAR technique (Sequense Characterized Amplifield
Region) because of their specialization.