Comprehensive analysis of morphological variation among 24 tomato (Solanum lycopersicum) genotypes oriented to ornamental breeding in Vietnam
ISSN 2588-1299
VJAS 2020; 3(1): 554-569
Vietnam Journal
of Agricultural
Sciences
Comprehensive Analysis of Morphological
Variation among 24 Tomato (Solanum
Lycopersicum) Genotypes Oriented to
Ornamental Breeding in Vietnam
Tran Thien Long1,2, Nguyen Hong Minh1,2, Nguyen Tuan Anh1,2,
Tran Thi Minh Hang3, Nguyen Thi Hoa4, Nguyen Tien Long1 &
Nguyen Thi Minh1
1High Quality Vegetable Research and Development Center, Vietnam National University
of Agriculture, Hanoi 131000, Vietnam
2Department of Plant genetics and breeding, Faculty of Agronomy, Vietnam National
University of Agriculture, Hanoi 131000, Vietnam
3Department of Horticulture and Landscape, Faculty of Agronomy, Vietnam National
University of Agriculture, Hanoi 131000, Vietnam
4Department of Plant Genetics and Breeding, Faculty of Agronomy, Vietnam National
University of Agriculture, Hanoi 131000, Vietnam
Abstract
Tomato is one of the most important vegetables cultivated in
Vietnam. Besides its regular consumption as a vegetable, a new
demand for using tomato as a decorative plant on special occasions
was identified in recent years. This study aimed to characterize new
tomato accessions on their desirable morphological traits to select
potential materials for further breeding programs of ornamental
tomato varieties in Vietnam. Twenty-four heirloom tomato
genotypes were evaluated on 19 morphological traits. Based on the
describing system for tomato developed by the International Plant
Genetic Resources Institute (IPGRI, 1996), significant variation was
assessed in both qualitative and quantitative traits related to fruit
morphology. The results of principle component analysis indicated
that three main principle components explained over 60% of the total
phenotypic variation. The five traits of fruit size, fruit shoulder shape,
fruit cross-sectional shape, number of locules, and shape of the pistil
scar were recommended as important traits for clustering tomato
genotypes in this study. In addition, the 24 genotypes were classified
at the coefficient of 0.39 into six different clusters. Finally, six
interesting accessions, AU66, AU67, AU68, AU73, AU79, and
AU83 (with strange fruit colors and shapes), were selected as
potential materials for further breeding programs of ornamental
tomato in Vietnam.
Received: December 23, 2019
Accepted: July 10, 2020
Correspondence to
Keywords
ORCID
Tran Thien Long
3414
Ornamental tomato breeding, cluster analysis, principle component
analysis
555
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
countries (Greene, 2012). This study aims to
characterize the morphological diversity among
new tomato genotypes originating from different
countries to identify desirable traits (mainly
related to fruit) for ornamental tomato breeding
programs. The results indicated significant
morphological variation among the 24 tomato
genotypes studied in terms of fruit-related traits.
Some accessions with interesting fruit shape and
color were selected for further breeding
programs of ornamental tomato in Vietnam.
Introduction
Tomato (Solanum lycopersicum) originated
in the Andean region of South America, was
domesticated in Mexico, spread to Europe in the
early 16th century, and later to the whole world
(Blanca et al., 2012). In 2017, tomato was the
most consumed vegetable worldwide with over
177 million tons produced for both fresh and
processing markets (Omondi, 2017). In Vietnam,
tomato has been cultivated for over 100 years and
has become one of the highest valued economic
vegetables for both the domestic market and
exporting (Ha, 2015).
Materials and Methods
Among many different breeding programs,
diversifying the germplasm is always defined as
one of the most important steps. The genetic
diversity data of many tomato germplasms have
been reported and used for different breeding
purposes such as developing elite inbred lines
(Wang et al., 2016; Kaur et al., 2019), predicting
potential heterosis between two parents in hybrid
tomato breeding (Jin et al., 2019), and
identifying valuable materials for specific
breeding targets. Some breeding targets of
greatest concern include: increasing fruit yield
components (Reddy et al., 2013; Ziaf et al.,
2016), improving fruit quality (Panthee et al.,
2013; Singh et al., 2018), and accelerating
adaptability to both biotic and abiotic stresses
(Panthee & Chen, 2010; Danso et al., 2011;
Hoagland et al., 2015; Hanson et al., 2016).
Plant materials
Twenty-four heirloom tomato genotypes
originating from America (15), Europe (8), and
Asia (1) were used in this study (Table 1). The
seeds were sown on nursery beds inside a net
house on 15 September 2018. After 30 days, the
seedlings were transplanted to an experimental
open field at a high-quality vegetable research
and development center, Vietnam National
University of Agriculture, Vietnam.
Experimental design
The experiment was designed following a
randomized complete block design (RCBD) with
two replications. Twenty-two plants of each
genotype were grown in an experimental plot
area of 8m2, planting two rows per bed; the plant
to plant spacing was 50cm, and the distance
between two rows was 60cm. All the genotypes
were grown under the same conditions and
standard agronomic management practices as
described by Srinivasan (2010).
In Vietnam, besides the above traditional
breeding targets, a new breeding consideration
for decorative plants has recently been identified
based on the trend of using agricultural crops for
ornamental purposes. Tomato has the potential to
lead the trend because of its diversity in different
traits, especially in the fruit shape, fruit color,
dwarf stem, simple or condensed leaf styles, and
long shelf-life (Martí et al., 2006; Saito et al.,
2011; Bhattarai et al., 2018). According to
Vegetable Gardening the Colonial Williamsburg
Way (Greene, 2012), many vegetables, including
tomato, have the potential for use as ornamental
plants in the garden due to their unique
morphological aspects. Tomato is currently
planted for both decorative and vegetable
purposes in botanic gardens in European
Data collection
Twenty-four tomato genotypes were
evaluated on 19 morphologic traits related to
plant structure, fruit morphology, and quality.
Each parameter was recorded as the average
performance of 6 different plants per genotype
per replication. For measuring the fruit
morphological traits (such as fruit length, fruit
width, etc.), 10 random fruits were used. The
measurements of 13 qualitative traits were used
for the clustering analysis. The measurements
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556
Tran Thien Long et al. (2020)
Table 1. The name, origin, and code of the 24 tomato genotypes in the experiment
Code for clustering
Code for clustering
Name
Origin
Code
Name
Origin
Code
analysis
OTU-1
OTU-2
OTU-3
analysis
Tigerella
Greenzebra
Black Krim
UK
AU66
AU67
AU68
Reisetomate
Tropic
Germany AU79
OTU-13
OTU-14
OTU-15
USA
USA
USA
AU80
AU82
Russia
Tommy Toe
Broad Ripple Yellow
Currant
USA
USA
USA
AU70
AU71
AU72
OTU-4
OTU-5
OTU-6
Moneymaker
UK
Italy
AU83
AU85
AU86
OTU-16
OTU-17
OTU-18
Campbell’33
Principe Borghese
Rouge de
Marmande
Roma
Spain
Beams Yellow Pear
Beefsteak
USA
USA
AU73
AU74
OTU-7
OTU-8
OTU-9
OTU-10
Jaune Flamme
Mortgage Lifter
Cherry Camp Joy
Cherry Cocktail
France
USA
USA
UK
AU87
AU88
AU89
AU91
OTU-19
OTU-20
OTU-21
OTU-22
Thai Pink Egg
Red Oxheart
Thailand AU75
USA
USA
USA
AU76
AU77
AU78
Cherry Yellow
Honeybee
Red Fig
Jubilee
OTU-11
OTU-12
USA
USA
AU92
AU93
OTU-23
OTU-24
Cherry Red Pear
were carried out according to the guidance of the
International Plant Genetic Resource Institute
(Ipgri, 1996) with modifications in measuring
leaf color and the presence of green (shoulders)
tops on the fruit (Table 2).
(accounting for 16.6%), 10 semi-determinate
(41.7%), and 10 indeterminate genotypes
(41.7%). The majority of the genotypes (17 out
of 24) had the standard leaf style while the other
7 genotypes had the peruvianum style.
Additionally, the 24 genotypes were allocated
into two main groups based on their leaf color
and intensity with 13 light green (54.1%) and 10
green (41.7%), while only 1 genotype had dark
green leaves (4.2%) (Table 3).
Data analyis
Analysis of variance (ANOVA) was
conducted using the Statistical Tool for
Agricultural Research (STAR) software with the
significance level of P< 0.05. Tukeys’s honest
significant difference test was used to separate
mean values at P< 0.05. A cluster analysis was
performed using the UPGMA clustering method
with NTSYSpc, version 2.10q (Rohlf, 2000). A
correlation analysis was performed using
Pearson’s method as described previously
(Hauke & Kossowski, 2011) and the principle
components were analyzed by Analyse-it
(Excel).
The main characteristics considered for
ornamental purposes in tomato are fruit
morphology, plant structure, and leaf type. This
study focused mainly on characterizing the fruit-
related traits of the experimental genotypes. One-
third of the genotypes had a simple flower
cluster, while two-thirds were complex in these
traits (Table 3 and Figure 1a). A higher complex
flower inflorescence is likely to be preferred for
decorative tomato. The phenotypes of the green-
mature fruit were also diverse with 3 white
shoulder genotypes (12%) and 3 slight green
shoulder genotypes (12%), while the majority
had exposed shoulders with green (7 genotypes)
or dark green (11 genotypes) colors, which
accounted for 29.2% and 45.8%, respectively
(Table 3 and Figure 1b).
Results
Diversity in morphological traits
A high level of diversity was observed
through both the vegetative and reproductive
traits among the 24 genotypes. In the plant
growth type, there were 4 determinate genotypes
Fruit shape and color are the most important
557
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
Table 2. Measuring scale used for tomato phenotyping
Traits
Measuring scale
IPGRI
Traits
Measuring scale
IPGRI
(1) Very small
(2) Small
(1) Dwarf
(2) Determinate
Plant growth
type* (GT)
7.1.2.1
Fruit size* (FS)
(3) Intermediate
(4) Large
7.2.2.6
(3) Semi- determinate
(4) Indeterminate
(5) Very large
(1) Dwarf
(2) Potato
(1) Green
(2) Yellow
(3) Orange
(4) Pink
(3) Standard
(4) Peruvianum
(5) Pimpinellifolium
(6) Hirsutum
(7) Other
Exterior color of
the mature fruit*
(ECOMF)
Leaf type* (LT)
7.1.2.9
7.2.2.11
(5) Red
(6) Other
(1) Light green
(2) Green
(3) Light
(5) Intermediate
(7) Dark
Intensity of the
exterior color*
(IOEC)
Leaf color
7.2.2.12
7.2.2.16
(3) Dark green
(1) Flat
(1) Generally uniparous
(3) Slightly depressed
(5) Moderately depressed
(7) Strongly depressed
Inflorescence
type* (IT)
(2) Partly uniparous, partly
multiparous
Fruit shoulder
shape* (FSS)
7.2.1.1
(3) Generally multiparous
(0) Absent
(3) Slightly
(1) Dot
Intensity of the
greenback (green
shoulder)*
Shape of the
pistil scar*
(SOPS)
7.2.2.2
7.2.2.3
(2) Stellate
(3) Linear
(4) Irregular
7.2.2.32
(5) Intermediate
(7) Strong
(IOGB)
(1) Flattened
(2) Slightly flattened
(3) Rounded
(1) Round
(2) Angular
(3) Irregular
Fruit cross-
sectional shape*
(FCSS)
7.2.2.29
7.2.2.33
(4) High rounded
(5) Heart shaped
(6) Cylindrical
(7) Pyriform
(1) Intended
(2) Flat
Fruit blossom
end shape*
(FBES)
Predominant fruit
shape* (PFS)
7.2.2.5
(3) Pointed
Fruit length
Fruit width
Quantitative
Quantitative
7.2.2.9
(8) Ellipsoid
7.2.2.10
(9) Other
Total soluble
solids*
Thickness of
pericarp
Quantitative
Quantitative
8.3.4
Quantitative
Quantitative
7.2.2.25
7.2.2.31
Number of seeds
per fruit
Number of
locules* (NOL)
Note: Traits marked with * were used for the clustering analysis; the abbreviations inside the brackets are presented in the biplot
chart of the pattern of PC1 and PC2 (Figure 4).
fruit traits for ornamental tomato. Among the 24
genotypes, 8 types of fruit shapes and 6 different
fruit colors were recorded. In terms of fruit
shape, besides the common shapes including
round, high round, or flat, some genotypes had a
very good looking shape such as water drop
(AU73 and AU77), heart shape (AU78 and
AU87), or pyriform shape (AU72). The
classification of the 24 genotypes based on fruit
shape can be seen in Table 3 and Figure 1c.
Similarly, the fruit color of the 24 tomato
genotypes was also highly diverse with some
interesting colors: 14 genotypes had red fruit
(58.4%), followed by 4 in yellow (16.7%), 2
each in orange and pink (8.3%), 1 in green
(4.2%), and 1 in black color (AU68- Black
karim) (Table 3 and Figure 1d). Combining the
observations on fruit shape and color, several
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558
Tran Thien Long et al. (2020)
Table 3. Classification of the 24 tomato genotypes based on morphological traits
Traits
Class
Number of genotypes
Frequency (%)
1. Dwarf
0
4
0
2. Determinate
16.6
41.7
41.7
Plant growth type
3. Semi-determinate
4. Indeterminate
10
10
1. Dwarf
2. Potato
0
0
0
0
3. Standard
4. Peruvianum
5. Pimpinellifolium
6. Hirsutum
7. Other
17
7
70.8
29.2
0
Leaf type
0
0
0
0
0
1. Light green
2. Green
13
10
1
54.1
41.7
4.2
Leaf color
3. Dark green
1. Generally uniparous
2. Partly uniparous, partly multiparous
3. Generally multiparous
8
0
33.3
0
Inflorescence type
16
66.7
0. White shoulder
3. Slightly
3
3
12.5
12.5
29.2
45.8
Intensity of the greenback
(green shoulder)
5. Intermediate
7. Strong
7
11
1. Flattened
2. Slightly flattened
3. Rounded
3
2
6
3
3
0
1
0
6
12.5
8.3
25.0
12.5
12.5
0
4. High rounded
5. Heart shaped
6. Cylindrical
7. Pyriform
Predominant fruit shape
4.2
0
8. Ellipsoid
9. Other
25.0
1. Green
2. Yellow
3. Orange
4. Pink
1
4
4.2
16.7
8.3
2
Exterior color of the
mature fruit
2
8.3
5. Red
14
1
58.3
4.2
6. Other
3. Light
5. Intermediate
7. Dark
2
20
2
8.3
83.4
8.3
Intensity of the exterior
color
1. Very small
2. Small
9
9
4
2
0
37.5
37.5
16.7
8.3
Fruit size
3. Intermediate
4. Large
5. Very large
0
1. Flat
13
2
54.2
8.3
3. Slightly depressed
5. Moderately depressed
7. Strongly depressed
Fruit shoulder shape
4
16.7
20.8
5
1. Round
2. Angular
3. Irregular
14
4
58.3
16.7
25.0
Fruit cross-sectional
shape
6
1. Dot
14
1
58.3
4.2
2. Stellate
3. Linear
4. Irregular
Shape of the pistil scar
Fruit blossom end shape
4
16.7
20.8
5
1. Intended
2. Flat
8
14
2
33.4
58.3
8.3
3. Pointed
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Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
Fruit shape
Inflorescence type
Intensity of greenback
8
6
4
2
0
15
10
5
20
15
10
5
0
0
Uniparous
Multiparous
r
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n
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(a)
(b)
(c)
Fruit size
Fruit color
Fruit shoulder shape
10
8
15
10
5
15
10
5
6
4
2
0
0
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t
Very small Small Intermediate Large
d
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(d)
Fruit cross-sectional shape
(e)
(f)
Fruit blossom end shape
Shape of the pistil scar
15
10
5
15
10
5
15
10
5
0
0
0
Round
Angular
Irregular
Dot
Stellate Linear Irregular
Intended
Flat
Pointed
(g)
(h)
(i)
Figure 1. Classification of the 24 tomato genotypes based on nine fruit-related traits
potential genotypes were identified for breeding
ornamental tomato varieties (Figure 2). AU66
and AU67 had un-uniform ripe fruit color, with
AU66 having red skin with orange stripes along
the fruit as its name Tigerella implies, while
AU67 (Greenzebra) had the unique fruit
coloration of green skin and some yellow stripes.
AU73 (Beams Yellow Pear) had yellow fruit
with a shape that looked like a water drop, and
AU79 (Reisetomate) had 6-11 separate small
fruits on one pistil in the first three inflorescences
(the data is not shown).
Vietnam Journal of Agricultural Sciences
560
Tran Thien Long et al. (2020)
AU66
AU67
AU73
(Tigerella)
(Greenzebra)
(Beams Yellow Pear)
AU87
AU68
AU79
(Jaune Flamme)
(Black Karim)
(Reisetomate)
Figure 2. Unique fruit morphologies of six tomato genotypes
Differences among the 24 experimental
genotypes were also observed in other fruit-
related traits. For fruit size, 9 genotypes (37.5%)
were identified in each of the very small fruit and
small fruit categories, 4 produced medium fruit
(16.7%) and 2 produced large fruit (8.3%)
(Table 3 and Figure 1e). In addition, there were
4 categories for fruit shoulder shape (from flat to
strongly depressed; Table 3 and Figure 1f), 3
groups for fruit cross-sectional shape (with the
round shape accounting for 58%; Table 3 and
Figure 1g), 4 categories for the shape of the pistil
scar (Table 3 and Figure 1h), and 3 categories
for fruit blossom end shape (Table 3 and Figure
1i). In general, almost all the categories of fruit-
related traits identified by IPGRI (1996) were
observed in the 24 experimental genotypes.
The observations on fruit morphology of the
24 genotypes had several distinguishable and
interesting phenotypes, such as un-uniform color
(AU66 with red with orange stripes and AU67
with green with yellow stripes), yellow-water
drop shape (AU73), round orange (AU83), and
black color (AU68). These fruit colors and
shapes will be considered for the further steps of
ornamental tomato breeding (Figure 2).
Quantitative fruit traits
A total of six quantitative fruit traits were
evaluated and compared. The results illustrated
561
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
significant differences (P< 0.05) among the 24
genotypes in all of the observed traits.
(from 5.35 to 416.0 seeds), and total soluble
solids (from 3.28% to 5.36%) (Table 4).
The fruit length and fruit width varied
significantly and could be used to classify the
experimental genotypes into four groups, from
tiny fruits such as AU70 and AU82, to large
fruits such as AU74 and AU88 (Table 4).
Statistically significant variation was recorded
among the 24 tomato genotypes in other traits,
including thickness of pericarp (varied from
0.18mm to 0.47mm), number of locules (from
2.0 to over 11 locules), number of seeds per fruit
Correlation analysis
Thirteen qualitative traits measured in this
study were analyzed for correlations. The results
indicated that fruit size had a significant positive
correlation with the fruit cross-sectional shape
(0.822), number of locules (0.765), and shape of
the pistil scar (0.850). Fruit shoulder shape was
significantly correlated with the number of
locules (0.747) and shape of the pistil scar
Table 4. Evaluation of six quantitative fruit traits. The data are presented as mean values (n=10); different letters within a column
represent significant differences (Tukeys’s honest significant difference test, P<0.05).
Fruit length
(cm)
Fruit width
(cm)
Thickness of
pericarp (cm)
Number of
locules
Number of seeds
per fruit
Total soluble
solids (%)
Genotype
AU66
AU67
AU68
AU70
AU71
AU72
AU73
AU74
AU75
AU76
AU77
AU78
AU79
AU80
AU82
AU83
AU85
AU86
AU87
AU88
AU89
AU91
AU92
AU93
LSD (0.05)
CV%
3.60 d-f
3.94 c-e
4.48 a-c
2.07 i
4.41 c-f
4.47 c-f
6.15 b
2.00 i
0.40 a-c
0.38 a-c
0.42 a-c
0.18 f
2.00 e
4.95 cd
8.42 b
2.00 e
4.70 d
2.15 e
2.00 e
8.38 b
2.10 e
9.08 b
2.00 e
5.00 cd
2.00 e
5.83 cd
2.00 e
2.00 e
2.10 e
6.60 c
2.20 e
11.39 a
2.00 e
2.00 e
2.00 e
2.00 e
1.7
77.60 c-f
25.50 i-k
86.71 b-e
65.80 d-h
70.60 d-h
34.00 h-k
62.90 d-h
115.38 b
65.10 d-h
5.33 k
4.53 a-d
4.63 a-d
4.21 a-d
5.12 ab
4.44 a-d
4.72 a-c
4.90 a-d
4.13 a-d
3.75 cd
4.27 a-d
3.94 b-d
4.80 a-c
3.80 b-d
4.37 a-d
3.62 cd
4.62 a-d
3.28 d
3.91 c-e
4.58 a-c
3.04 f-h
4.93 a
4.77 b-e
2.87 g-i
2.28 i
0.40 a-c
0.34 b-e
0.23 ef
0.44 ab
0.31 c-e
0.30 c-f
0.24 d-f
0.33 b-e
0.19 f
8.16 a
3.25 e-i
4.79 b-e
2.46 i
3.50 d-g
3.52 d-g
3.47 d-g
3.06 f-h
3.00 f-h
4.47 a-c
2.65 hi
4.04 b-d
3.24 e-h
3.92 c-e
3.88 c-e
4.77 ab
2.65 hi
2.99 f-h
2.66 hi
2.78 g-i
0.77
48.30 f-i
7.25 jk
4.09 d-h
5.80 bc
6.02 b
3.00 f-i
4.97 b-d
2.95 f-i
6.09 b
4.41 c-g
8.19 a
2.96 f-i
3.21 f-i
2.78 hi
2.97 f-i
1.55
416.00 a
46.58 f-i
38.90 g-k
95.20 b-d
52.60 e-i
74.00 c-g
109.90 bc
116.50 b
33.90 h-k
51.70 e-i
43.50 f-j
39.70 g-k
37.30
0.33 b-e
0.37 a-d
0.41 a-c
0.36 a-d
0.39 a-c
0.47 a
3.78 b-d
5.36 a
0.41 a-c
0.34 b-e
0.38 a-c
0.31 c-f
0.34 b-e
0.13
4.12 a-d
4.19 a-d
4.19 a-d
3.96 b-d
4.26 a-d
1.35
5.30
8.81
8.98
10.43
12.26
7.69
Vietnam Journal of Agricultural Sciences
562
Tran Thien Long et al. (2020)
Figure 3. Biplot presents the contribution of the correlation of observed scores (t(corr)) of the 24 genotypes (colored hexagons) and
the loading scores (p(corr)) of 13 traits (grey stars) to the PC1 (horizontal axis) and PC2 (vertical axis). Four groups (represented by
four different colors) were classified among the experimental genotypes.
(0.694). Significant positive correlations were
also observed between the fruit cross-sectional
shape and number of locules (0.752), and the
shape of the pistil scar (0.896). Finally, the
number of locules was correlated significantly
with the shape of the pistil scar (0.793). Other
correlations were non-significant (Table 5).
Based on the loading scores (Table 7) and
the positions of the grey stars, which are far away
from the PC origin along the horizontal axis
(Figure 3), five traits (fruit size, fruit cross-
sectional shape, shape of the pistil scar, number
of locules, and fruit shoulder shape) had a strong
influence on PC1. The representative grey star of
intensity for the greenback trait is far from the PC
origin along the vertical axis, indicating that this
trait contributed mostly to PC2 (Figure 3, Table
7). The data shown in Table 7 also illustrate that
PC3 included growth type, leaf type, and
predominant fruit shape, while the two traits
inflorescence type and intensity of exterior color
were important in PC4 (Table 7).
Principle Component Analysis
The results of the principle component
analysis (PCA) of 13 phenotypic traits are
presented in Table 6, Table 7, and Figure 3. The
results indicated that the variance in PC1, PC2,
PC3, and PC4 could explain 71.1% of the total
variation. The contributions of these four main
principle components were 35.8%, 12.7%,
11.9%, and 10.7%, respectively (Table 6).
In addition, the angles between the vectors
(red dashed lines in Figure 3) that connect the
563
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
PC origin to the grey stars indicate the
correlations between the characteristics. The
smaller the angle is, the more positive the
relationship is between two characteristics; in
contrast, an angle of nearly 900 indicates no
correlation between two traits. The results
showed significant positive correlations among
the five main traits of PC1 (the correlation values
are described in Table 5) while the main
influential trait of PC2, intensity of the
greenback, and three traits related to plant
structure, growth type, leaf type, and
inflorescence type, had minimal correlation
values with the group of five main traits of PC1
(Figure 3, Table 5).
morphological traits. The similarity coefficient
among the practical genotypes ranged from 0.25
to 0.93 with the two most similar genotypes
being AU77 (OUT-11) and AU93 (OUT-24). At
the coefficient of 0.39, the twenty-four tomato
genotypes in this study were classified into six
clusters (Figure 4). The frequencies, typical
characteristics, and names of the genotypes in
each cluster are presented in Table 8. The results
showed that fruit size, fruit color, and
morphology of the fruit shoulder were the most
important characters to distinguish these six
groups.
Discussion
The component pattern based on PC1 and
PC2 is exposed in the two-dimensional chart in
Figure 3. The chart shows four groups of
genotypes, which are represented by four
different colors, and the differences among the
groups are produced by the corresponding traits.
In more detail, group 1 (green) includes AU68,
AU74, and AU88. These genotypes can be
separated from the others by their fruit size, fruit
shape, number of locules, and shape of the pistil
scar. Group 2 (blue) includes AU71, AU76,
AU78, AU79, AU80, AU86, and AU88. These
genotypes tend to be different from the others
based on the traits of intensity of the greenback,
external color of the mature fruit, and
inflorescence type (Figure 3). Group 3 (red)
contains AU66, AU67, AU72, AU75, and AU87,
and the intensity of the greenback and fruit
blossom end shape are the two traits specifying
this group (Figure 3). Finally, group 4 includes
the remaining 8 genotypes that are similar in
growth type and external color of the mature fruit
(Figure 3). The details of the typical
characteristics of the genotypes in each group are
presented in Table 8 with the note that the
clusters presented in Figure 4 and Table 8 are
not exactly the same as the groups in Figure 3
because the groups are classified based on the
pattern of PC1 and PC2 only while the clusters in
Figure 4 are based on the differences in all the
experimental traits among the 24 genotypes.
Evaluations of tomato diversity based on
morphological traits have been conducted and
reported previously in many studies. This study
illustrated that three main PCs explained over
60% of the phenotypic variation and the main
traits contributing to the first and second PCs
were fruit size, fruit shape, fruit shoulder shape,
number of locules, shape of the pistil scar, and
intensity of the green shoulder. These results are
in accordance with many previous reports: fruit
size and fruit shape were important components
of the main PCs that have been illustrated in
studies on tomato diversity evaluation conducted
in the USA and Argentina (Hu et al., 2012;
Bhattarai et al., 2016). Another fruit-related trait,
the number of locules, has also been suggested as
a major trait to distinguish tomato genotypes
(Glogovac et al., 2012). The presence of a green
shoulder was reported as the most important
contributor (with five other traits) of PC1
(Tembe et al., 2018). The fruit shoulder shape
was one of two main traits contributing to PC1
reported in a study in Nigeria (Ao et al., 2017)
However, several other traits that were not fruit-
related or were evaluated as non-significant
contributors for the main PCs in this study, such
as bio-chemical traits and leaf traits, were
reported as the main components to distinguish
the experimental genotypes in other studies in
Spain and Serbia (Glogovac et al., 2012;
Cebolla-Cornejo et al., 2013). Conversely, the
results of this present study suggested that the
shape of the pistil scar should be considered as
Cluster analysis of the 24 tomato genotypes
The twenty-four tomato genotypes were
clustered based on the evaluation of 14
Vietnam Journal of Agricultural Sciences
564
Tran Thien Long et al. (2020)
Table 5. Pearson correlation coefficients between 13 traits of the 24 tomato genotypes
Intensity
of the
greenback
(green
Exterior
color of
the
mature
fruit
Pre-
dominant
fruit
Intensity
of the
exterior
color
Fruit
cross-
sectional
shape
Shape
of the
pistil
Fruit
blossom
end
Fruit
shoulder
shape
Number
of
locules
Growth
type
Leaf
type
Inflorescence
type
Fruit
size
Pearson's r
shape
scar
shape
shoulder)
Growth type
Leaf type
1.000
0.159
0.000
0.365
0.142
-0.108
-0.084
0.000
-0.105
-0.068
0.052
-0.092
-0.146
1.000
-0.324
-0.247
0.204
Inflorescence type
1.000
0.202
0.165
-0.032
0.150
-0.217
0.237
0.243
0.079
0.140
0.000
Intensity of the greenback (green shoulder)
Predominant fruit shape
Fruit size
1.000
-0.029
-0.171
0.180
0.218
0.028
0.007
0.105
0.099
-0.382
1.000
0.135
0.089
-0.107
0.110
0.298
0.176
0.128
-0.196
-0.168
-0.211
-0.225
-0.243
-0.072
-0.111
-0.219
-0.039
1.000
0.233
0.328
0.612
0.822*
0.765*
0.850*
-0.468
Exterior color of the mature fruit
Intensity of the exterior color
Fruit shoulder shape
1.000
0.149
0.314
0.333
0.175
0.265
-0.204
1.000
0.247
0.120
0.195
0.324
-0.171
1.000
0.645
Fruit cross-sectional shape
Number of locules
1.000
0.752*
0.896*
-0.412
0.747*
0.694*
-0.324
1.000
0.793*
-0.484
Shape of the pistil scar
Fruit blossom end shape
1.000
-0.445
1.000
Note: * is significant at the < 0.05 probability level.
565
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
Table 6. The contributions of the principle components to variation among the 24 experimental genotypes based on 13
qualitative traits
Component
Variance
Proportion
Cumulative proportion
1
2
4.657
1.652
1.546
1.393
0.890
0.713
0.632
0.472
0.423
0.357
0.154
0.063
0.047
0.358
0.127
0.119
0.107
0.068
0.055
0.049
0.036
0.033
0.027
0.012
0.005
0.004
0.358
0.485
0.604
0.711
0.780
0.835
0.883
0.920
0.952
0.980
0.992
0.996
1.000
3
4
5
6
7
8
9
10
11
12
13
Table 7. Contributions of each qualitative trait to the main principle components
Traits
Growth type
PC1
PC2
PC3
PC4
0.051
0.248
-0.195
-0.138
-0.227
-0.881
-0.399
-0.341
-0.809
-0.900
-0.876
-0.933
0.575
0.497
-0.400
0.365
0.894
-0.058
-0.295
0.256
0.198
-0.044
-0.162
-0.073
-0.084
-0.277
0.598
0.706
-0.174
0.103
0.575
-0.011
-0.214
-0.256
-0.148
0.103
0.138
-0.046
-0.393
0.125
0.108
-0.778
0.124
-0.420
0.154
-0.151
0.658
-0.097
-0.182
0.050
0.048
-0.205
Leaf type
Inflorescence type
Intensity of the greenback (green shoulder)
Predominant fruit shape
Fruit size
Exterior color of the mature fruit
Intensity of the exterior color
Fruit shoulder shape
Fruit cross-sectional shape
Number of locules
Shape of the pistil scar
Fruit blossom end shape
an important trait for the main PCs (Table 5),
which has not been reported in any previous
study.
Another aim of this study was to select
suitable materials for ornamental tomato
breeding. The results show that some genotypes
have interesting traits, such as rare color or
strange shape, that can be used for ornamental
breeding. Previously, many reports have
identified the genetic mechanisms of how tomato
fruit shape and color are regulated. For example,
different fruit colors in tomato are controlled
independently or in interaction(s) among a group
of genetic elements. Red tomato fruit is the most
common color in nature (wild type) as well as in
commercialized varieties, while the other colors
are created on the background of this red color
with different mutation(s). For instance, yellow
Vietnam Journal of Agricultural Sciences
566
Tran Thien Long et al. (2020)
Figure 4. Cluster analysis of the 24 tomato genotypes based on 14 phenotypic traits (The analysis was conducted in NTSYSpc,
version 2.10q using the UPMGA clustering method. The first dashed red line crosses the coefficient value of 0.39 which separates
the 24 genotypes into 6 clusters while the second line is to identify the highest similar genotypes: AU77 and AU93 with a coefficient
value of 0.93)
Table 8. Six clusters derived from clustering the 24 tomato genotypes by UPMGA method
Cluster Frequency
Typical characters
Genotype(s)
I
4
White/slight green shoulder, small-red fruit, and flat
fruit blossom end
AU66, AU67, AU78, AU83
II
11
Indeterminate growth type, very small- red-round
fruit, dotted pistil scar shape
AU70, AU72, AU73, AU77, AU82, AU85, AU87,
AU89, AU91, AU92, AU93
III
1
1
Dark green and moderately depressed fruit shoulder
AU71
AU75
IV
Determinate growth type, white fruit shoulder, pink
color
V
6
1
Medium to large fruit size, irregular fruit shape and
pistil scar, many locules per fruit
AU68, AU74, AU79, AU80, AU86, AU88
AU76
VI
Dark green fruit shoulder, orange color, many locules
is a recessive mutation on the R locus while while
pink, orange, and green colors are controlled by
mutation(s) on the Y locus, B and Del loci, and
Gf locus, respectively (Liu et al., 2003).
Conversely, black color is not naturally present
in cultivated tomato but can be regulated by the
genes Aft, atv, and abg from wild species (Jones
et al., 2003; Canady et al., 2006; Mes et al.,
2008). Similarly, tomato shape expression and
control were also investigated comprehensively.
Nine main shape categories were identified in
tomato fruit (Visa et al., 2014) and four regions
on chromosomes 2, 3, 7, and 8 carried the main
loci related to the regulation of tomato fruit shape
(Brewer et al., 2007). Overall, understanding the
genetic regulation models of all colors and
shapes in tomato enables researchers to use
suitable breeding methods to create tomato
materials with expected colors and shapes (for
different ornamental purposes). In fact, some
commercialized tomato cultivars were released
for ornamental purposes by combining
appropriate decorative traits, such as Sweet
Valentine F1 (with a compact plant structure: 30-
40cm in height, spread 30-35cm; red heart-
shaped fruit). The new fruit colors and shapes
567
Comprehensive analysis of morphological variation among 24 tomato genotypes oriented to ornamental breeding
genotyping and morphology provides insight into the
origin of the tomato. PloS One. 7(10): e48198.
found in this study provide many ideas for
ornamental breeding by combining interesting
fruit morphologies with different plant structures
(such as dwarf stem) and leaf types depending on
Brewer M. T., Moyseenko J. B., Monforte A. J. & van der
Knaap E. (2007). Morphological variation in tomato: a
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Canady M. A., Ji Y. & Chetelat R. T. (2006). Homeologous
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recombination
in
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lycopersicoides
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174(4): 1775-1788.
The present study evaluated significant
variation in 19 morphological characteristics
including both qualitative and quantitative traits
among 24 tomato genotypes. The 24 genotypes
were also divided into 6 clusters based on the
differences among 13 qualitative characteristics.
The results of principle component analysis
identified that three main PCs explained over
60% of the total phenotypic variation. In
addition, six fruit traits (fruit size, fruit cross-
sectional shape, fruit shoulder shape, number of
locules, shape of the pistil scar, and intensity of
the greenback) were recommended as important
components of PC1 and PC2 in this study.
Finally, six interesting accessions (with strange
fruit colors and shapes) were identified as
potential materials for further breeding programs
of ornamental tomato (AU66, AU67, AU68,
AU73, AU79, and AU87).
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This work was supported by Vietnam
National University of Agriculture under the
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