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SABRAO Journal
of Breeding and Genetics
44 (2) 302-321, 2012
BREEDING TOMATO (Solanum lycopersicum L.) FOR HIGHER
PRODUCTIVITY AND BETTER PROCESSING QUALITIES
VARUN DURWAS SHENDE1, TANIA SETH2, SUBHRA
MUKHERJEE1 and ARUP CHATTOPADHYAY3*
1Department of Plant Breeding, Faculty of Agriculture, Bidhan Chandra Krishi Viswavidyalaya,
Mohanpur-741252, Nadia, West Bengal, India
2Department of Vegetable Crops, Faculty of Horticulture, Bidhan Chandra Krishi
Viswavidyalaya, Mohanpur-741252, Nadia, West Bengal, India
3All India Coordinated Research Project on Vegetable Crops, Directorate of Research,
Bidhan Chandra Krishi Viswavidyalaya, Kalyani-741235, Nadia, West Bengal, India
* Corresponding author’s email: chattopadhyay.arup@gmail.com
SUMMARY
Tomato (Solanum lycopersicum L.) has the potential for improvement through
heterosis breeding which can further be utilized for development of desirable
recombinants. A 3 × 3, line × tester mating design was used to determine heterosis
over better parent, combining ability and gene action for eleven characters in tomato.
Preponderance of non-additive gene action was evident for control of all characters
studied except TSS content of fruit for which both additive and non-additive gene
actions were evident. Amongst the parental lines, ‘CLN2498-D’, ‘CLN2762-A’ and
‘BCT-110’ were the best general combiners for fruit yield and component characters
along with good processing traits and thus could be used in tomato hybridization
programs. Crosses showing high specific combining ability (SCA) for fruit yield
involved parents showing high general combining ability (GCA) for numbers of fruit
per flower cluster or numbers of fruit per plant or fruit weight or fruit diameter. The
promising hybrids of the CLN2498-D x DVRT-2 and CLN2777-C x BCT-53 were
selected on the basis of their performance per se; heterosis manifested in them and the
SCA effects. These two hybrids could be used commercially for high yield. However,
the cross CLN2498D x BCT-110 could be exploited for better processing qualities.
Keywords: combining ability, gene action, heterosis, processing quality, tomato
Manuscript received: February 2, 2012; Decision on manuscript: June 28, 2012; Manuscript
accepted in revised form: August 2, 2012.
Communicating Editor: C. Ravindran
RESEARCH ARTICLE
Shende et al. (2012)
303
INTRODUCTION
Tomato (Solanum lycopersicum) is
one of the important Solanaceous
vegetable crops of Peru-Ecuador
origin (Rick, 1969) and used as
fresh vegetable as well as raw
material for processed products
such as juice, ketchup, sauce,
canned fruits, puree, paste, etc.
Apart from contributing nutritive
elements, colour and flavour to the
diet, tomatoes are also a valuable
source of antioxidants, or chemo-
protective compounds, and may
thus be termed as "functional food"
(Ranieri et al., 2004). The desirable
qualities for a tomato cultivar to be
used for processing includes high
total soluble solids (4-8° brix),
acidity not less than 0.4 %, pH less
than 4.5, uniform red color, smooth
surface, free from wrinkles, small
core, firm flesh and uniform
ripening (Adsule et al., 1980).
Throughout the last
century, tomato varietal
improvement program has been
based on various standard breeding
methods, including the pedigree
method of hybridization followed
by backcrossing of desired traits
from one parent into another,
which has resulted in generation of
improved tomato varieties and
hybrids with high quality and yield.
Tomato improvement occurred due
to increasing exploitation of exotic
resources and introgression of new
valuable genes into the tomato
gene-pool. Classical breeding has
not only developed cultivars with
monogenic and dominant
resistance for controlling certain
plant pathogens or F1 hybrids by
combination of resistances, as for
example, H-24 developed by
Kalloo and Banerjee (2000), was
used in developing ToLCV tolerant
breeding lines for development of
promising hybrids (Hazra et al.,
2009) but has also enabled the
acquisition of good, value-added
agronomic traits, such as high
fertility and fruit setting, earliness,
uniform ripening, adaptation,
firmness and long shelf-life
appropriate for shipping to distant
markets. The replacement of inbred
lines by hybrids has remarkably
increased yield, while the genetic
gain rate has been reduced due to
low genetic diversity within
processing tomatoes (Grandillo et
al., 1999). This suggests that the
introduction of hybrids, after the
first positive impact, made no
further contribution to a positive
genetic gain in yield.
Tomato breeders prefer
hybrid breeding to varietal
breeding, not only because it is
comparatively easier to incorporate
desirable characteristics in F1
hybrid but also the right of the bred
hybrid is protected in terms of
parental lines (Kumar and Singh,
2005). Moreover, despite high cost
of hybrid tomato seeds, there has
been added advantage to the
farmers in cultivation of hybrid
tomatoes. This is because under
optimum crop production and
protection management, crop
raised from the hybrid seeds has
several advantages like better yield
and adaptability, uniformity and
reactions to certain biotic and
abiotic stresses in comparison to
crop raised from the seeds of
improved pure line or open
pollinated varieties.
Genetic analysis provides a
guide line for the assessment of
relative breeding potential of the
parents or identify best combiners
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
304
in crops (Khattak et al., 2004;
Weerasingh et al., 2004; Sulodhani
Devi et al., 2005) which could be
utilized either to exploit heterosis
in F1 or the accumulation of fixable
genes to evolve variety. Such
studies not only provide necessary
information regarding the choice of
parents but also simultaneously
illustrate the nature and magnitude
of gene action involved in the
expression of desirable traits. The
impulse of progress in crop
improvement through plant
breeding was propelled by a better
understanding and an appropriate
exploitation of heterosis, the
classical term coined by Shull
(1914) implying the gain in
vigour on crossing two inbreds. A
considerable degree of heterosis
has been documented and utilized
in tomato for various characters
ever since the first official report
by Hedrick and Booth (1907).
Tomato is a self pollinated crop,
where degree of heterosis was
theoretically considered less
(Gallias, 1988). However, the
unusual high heterosis observed in
tomato crop has been attributed to
the fact that tomato was basically
a highly out crossing genus which
was later evolved into a self
pollinated crop (Rick, 1965).
Heterosis manifestation in tomato
is in the form of the greater vigour,
faster growth and development,
earliness in maturity, increased
productivity, better quality
attributes, and higher levels of
resistance to biotic stresses
(Yordanov, 1983; Mahendrakar et
al., 2005; Seeja et al., 2007;
Hannan et al., 2007; Gul et al.,
2010; Chattopadhyay et al., 2011).
Even though many studies have
been made on combining ability,
gene action and heterosis, the pace
of work on development of tomato
hybrid on commercial basis have
been limited due to lack of superior
combiners in India. Line × tester
technique (Kempthorne, 1957) is
one of the best techniques that
provide information about general
and specific combining ability of
the parents and at the same time, it
is helpful in estimating various
types of gene effects.
Keeping in view the
importance of the above studies,
the present research program has
been undertaken to determine the
nature and magnitude of heterosis
over mid- and better-parent for
yield component and processing
characters of tomato and to
determine the nature of gene action
for these traits with a view to
identify good general combiners, as
well as to frame the breeding
strategies for the genetic
improvement of such characters.
MATERIALS AND METHODS
The investigation was carried out
during 2009 to 2011 at Research
Farm of Bidhan Chandra Krishi
Viswavidyalaya, Kalyani, Nadia,
West Bengal, India under the
research field of All India
Coordinated Research Project on
Vegetable Crops, situated at 23.50
N latitude and 890 E longitude at a
mean sea level of 9.75m.
Development of F1 hybrids and
field trials
Seeds of lines CLN2762-A,
CLN2498-D and CLN2777-C
imported from Asian Vegetable
Research and Development Centre,
Shende et al. (2012)
305
Taiwan and the testers DVRT-2,
BCT-53 and BCT-110 of Indian
origin were used for the study.
Seed beds were prepared in a sandy
loam soil and were 20 cm high and
1.0 m wide. Weathered cowdung
manure at 4 kg/m2 was mixed into
the beds. Beds were drenched with
formaldehyde (4.0%) and covered
with polythene sheet for 10 days to
avoid damping off disease. Seeds,
after treatment with Thiram (3 g/kg
of seed), were sown during the 3rd
week of August, 2009 at a shallow
depth 5 cm apart and covered with
finely sieved well rotten leaf mold
(leaves left to decompose for two
year) which acts as soil improver
and to prevent the soil drying out.
After sowing, beds were covered
with straw until germination which
normally takes five to seven days
and hand watered regularly up to
1st week of September, 2009.
Nursery beds were covered with
200 μm ultraviolet (UV)-stabilized
polyethylene film supported by
bamboo poles with open sides to
protect seedlings from rain and
direct sunlight. Seedlings were
hardened by withholding water 4
days before transplanting. Twenty
five days old seedlings were
transplanted to the main field
during 2nd week of September,
2009. Three lines and three testers
were planted in each plot consisted
of 20 plants spaced by 60 cm in 2
rows, each of which are 6 m long.
Management practices for
cultivation were followed as per
Chattopadhyay et al. (2007).
During full boom, crossing was
carried out. Flowers of each line
were emasculated between 4.00
and 5.30 p.m. Male parent flower
buds that would open the following
day were picked in the afternoon,
the anthers were separated that
night to dry and the pollen were
extracted the following morning
for pollination, which was done
from 8 to 10 a.m. Each parental
line was crossed with each tester
separately. Hybrid seed were
extracted by the fermentation
method (Rashid and Singh, 2000).
The red ripe finely chopped fruits
were kept for overnight for
fermentation in a plastic bucket.
This process removes the mucilage
and makes the seeds free from
adhering pulp which settles down
at the bottom. Then it was washed
thoroughly with clean water in the
next day morning. Seeds which
were floated in the water along
with pulp were discarded and the
decanted seeds were taken out,
dried and stored in desiccators for
sowing in the next season.
In the next year, the same
method was followed for raising
the seedlings of 6 parental lines
and 9 hybrids and one-month-old
seedlings were transplanted in the
2nd week of September, 2010. The
parents and hybrids were planted in
a randomized complete block
design with 3 replications at 60 ×
60 cm spacing with 36 plants for
each replication in a 3.6 × 3.6 m
plot. The plant protection measures
against early blight and tomato leaf
curl virus diseases were taken up in
time. Observations were recorded
from fifteen randomly selected
plants from each parental line and
hybrid on plant height (cm), days
to 50% flowering, numbers of
flower cluster plant-1, numbers of
fruit flower cluster-1, numbers of
fruit plant-1, fruit weight (g), polar
diameter of fruit (cm), equatorial
diameter of fruit (cm), total soluble
solids (o brix) (by digital hand
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
306
refractometer), titratable acidity (%
in terms of citric acid) (AOAC
1984), and fruit yield plant-1 (kg).
Plant height, numbers of flower
cluster plant-1, numbers of fruit
flower cluster-1 were recorded after
last appearance of flower cluster;
days to 50% flowering was taken
when 50% plants bear first flower;
numbers of fruit flower cluster-1,
numbers of fruit plant-1 were
counted after fruit setting of last
flower cluster; fruit weight, polar
and equatorial diameter of fruit,
total soluble solids, titratable
acidity were recorded from the
latest-set (youngest) fully ripened
fruits; and fruit yield plant-1 was
computed by adding the weight of
total fruits from different pickings
from each of the reference plant in
each entry.
Statistical analyses
Data were analyzed with the line x
tester model of genetic analysis
(Kempthorne, 1957). Heterosis
over better-parent (Heterobeltiosis)
was estimated in terms of per cent
increase or decrease of the F1
hybrid over its better-parent (Hayes
et al., 1965) using the following
formula.
Heterobeltiosis (%) = [(F1-BP)/BP]
x 100
Significance of better parent
heterosis was determined following
the “t” test suggested by Wynne et
al. (1970).
S.E. (BP) = √ (2 EMS/r); t value =
Heterobeltiosis / S.E. (BP)
Calculated t was tested against
table value of t at error d.f. for test
of significance where,
MP= Mean of mid-parent in the
cross;
BP = Mean of better-parent in the
cross;
EMS = Error mean square;
r = Number of replication;
d.f. = Degrees of freedom.
Combining ability analysis was
carried out according to Nadarajan
and Gunasekaran (2008) based on
Griffing’s (1956) fixed effect
model using the following formula:
Yij = m + gi +gj + sij + rij + 1/bc
ΣΣ
ijkl
where
i, j = 1, 2……...n;
k = 1, 2,……b.
l = 1, 2,.............c;
Yij is the mean of i × j genotype
over k and l;
m is the population mean;
gi is the GCA effect of the ith
parent; gj is the GCA effect of the
jth parent; sij is the SCA effect; rij is
the reciprocal effect; and
1/bc
ΣΣ
ijkl is the mean error effect.
SPAR I (developed by the
Indian Agricultural Statistics
Research Institute, New Delhi,
India) software was used for
statistical analysis. Data were
subjected to analysis of variance
(Panse and Sukhatme, 1984).
Heterobeltiosis was computed by
using computer software program
Windowstat 8.0 (developed by
Indostat Services 18, Ameerpet,
Hyderabad, India).
Shende et al. (2012)
307
RESULTS
Nature of gene action
The general and specific
combining ability are the main
criteria of rapid genetic assaying of
the test genotypes under line x
tester analysis. Combining ability
variances were significant for line
x tester in most of the characters
(Table 1). Line x tester component
of genetic variation was not
significant for days to 50%
flowering. Two variances (GCA
and SCA) showed wide range of
variation for all the characters
studied. Additive variance (α2A)
and dominance variance (a2D) can
be calculated at F=l (tomato being
self pollinated crop) from GCA and
SCA variances (Nadarajan and
Gunasekaran, 2008). In this
prediction α2D = 2 α2GCA and α2H
= α
2SCA. A general trend of the
genetic control of the characters
can be ascertained from these
estimates of additive and non-
additive variance components. The
relative importance of the additive
and non-additive genetic effects for
these characters was reflected by
the predictability ratio α2 D/ (α2 H
+ α2 D) as per Baker (1978). The
closer this ratio is to unity, the
greater the predictability based on
GCA alone.
The results presented in
Table 2 indicated that
predominance of non-additive gene
action was evident for control of
characters namely, plant height,
days to 50% flowering, number of
flower clusters plant-1, number of
fruits flower cluster-1, number of
fruits plant-1, fruit weight, polar
diameter, equatorial diameter, fruit
acidity and fruit yield plant-1 as the
proportion of additive genetic
variance in the total genetic
variance was much less for these
traits. However, the proportion of
additive genetic variance for TSS
content of fruit was in equal
magnitude with that of total genetic
variance. In such case, both
additive and non-additive gene
actions were important for the
conditioning of TSS content of
fruit.
GCA and per se performance
The per se performance and GCA
effects of the parents used in the
study for eleven characters are
given in Table 3. After the
assessment of overall picture of
GCA effects, it appeared that the
parents differ in their GCA.
Among the lines, the highest
significant and positive GCA
effects had shown by CLN2498-D
for maximum number of characters
namely, numbers of flower cluster
plant-1, numbers of fruit flower
cluster-1, numbers of fruit plant-1,
fruit weight, polar diameter,
equatorial diameter, fruit acidity
and fruit yield plant-1.
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
308
Table 1. Analysis of variance for combining ability of eleven characters of tomato.
PH=Plant height; D50F= Days to 50% flowering; NFCPP= Numbers of flower cluster plant-1; NFPC= Numbers of fruit flower cluster-1; NFPP= Numbers of fruit plant-1;
FW= Fruit weight; PD= Polar diameter; ED= Equatorial diameter; TSS=Total soluble solids; ACD= Acidity; FYPP= Fruit yield plant-1
*, ** Significant at P <0.05 and 0.01, respectively.
Source of
variation
(d.f.)
Mean Sum of Square for parents and hybrids for the character
PH D50F NFCPP NFPC NFPP FW PD ED TSS ACD FYPP
Replication
(2) 0.06 0.42 0.01 0.00 0.01 0.20 0.00 0.0004 0.002 0.0004 0.0001
Lines
(2) 405.83* 13.81** 20.13 0.40 666.44 444.20* 1.38 1.84 1.84** 0.004 6.18**
Testers
(2) 220.89 9.15* 5.82 0.09 62.44 127.30 0.24 0.10 0.10 0.01* 0.12
Line x Tester
(4) 74.82** 2.37 21.55** 0.20** 383.15** 123.30** 0.73** 0.63** 0.70** 0.003** 0.44**
Error
(28) 0.02 1.07 0.01 0.0001 0.021 0.11 0.0001 0.0001 0.01 0.0001 0.0001
Shende et al. (2012)
309
Table 2. Estimates of component of variance for eleven characters of tomato.
PH=Plant height; D50F= Days to 50% flowering; NFCPP= Numbers of flower cluster plant-1; NFPC= Numbers of fruit flower cluster-1; NFPP= Numbers of fruit plant-1;
FW= Fruit weight; PD= Polar diameter; ED= Equatorial diameter; TSS=Total soluble solids; ACD= Acidity; FYPP= Fruit yield plant-1
Component of
genetic variance PH D50F NFCPP NFPC NFPP FW PD ED TSS ACD FYPP
σ2 GCA 6.63 0.25 -0.24 0.001 -0.52 4.51 0.002 0.009 0.05 0.0001 0.08
σ2 D (2 x σ2 GCA) 13.25 0.51 -0.48 0.003 -1.04 9.02 0.004 0.02 0.91 0.0002 0.15
σ2 H (σ2 SCA) 64.69 1.95 5.75 0.07 124.59 68.14 0.26 0.27 0.50 0.002 0.60
σ2 H/ σ2 D 4.88 3.85 -12.06 28.38 -119.86 7.55 61.69 14.23 5.54 9.00 3.97
Predictability
Ratio
σ2 D/ (σ2 H + σ2 D)
0.17 0.21 0.09 0.03 0.01 0.12 0.02 0.07 0.64 0.10 0.20
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
310
Table 3 Estimates of general combining ability effects and per se performance (in parentheses) in six parents over nine F1s.
PH=Plant height; D50F= Days to 50% flowering; NFCPP= Number of flower cluster plant-1; NFPC= Number of fruit flower cluster-1; NFPP= Number of fruit plant-1;
FW= Fruit weight; PD= Polar diameter; ED= Equatorial diameter; TSS=Total soluble solids; ACD= Titratable Acidity; FYPP= Fruit yield plant-1
*, ** Significant at p<0.05 and 0.01, respectively.
Parents PH D50F NFCPP NFPC NFPP FW PD ED TSS ACD FYPP
CLN2762-A 6.91** -0.48 0.06* 0.10** 1.59** -0.69** -0.30** -0.37** 0.78** 0.02** 0.01**
(81.07)
(42.00)
(12.63)
(3.53)
(44.57)
(62.07)
(4.23)
(4.17)
(4.30)
(0.47)
(2.78)
CLN2498-D
-0.41**
-0.93*
1.46**
0.14**
7.70**
7.34**
0.44**
0.50**
-0.30**
0.01*
0.82**
(75.47) (42.00) (15.03) (3.43) (51.07) (64.77) (4.32) (4.76) (3.50) (0.41) (3.33)
CLN2777-C -6.50** 1.41** -1.53** -0.24** -9.29** -6.66** -0.14** -0.13** -0.49** -0.03** -0.84**
(61.47) (44.67) (12.30) (3.36) (41.20) (44.93) (3.72) (3.80) (3.40) (0.43) (1.85)
DVRT-2
-0.36**
-1.15**
0.75**
-0.11**
0.40**
-3.41**
-0.19**
0.06**
-0.05
0.04**
-0.14**
(56.67)
(41.67)
(17.40)
(2.47)
(42.70)
(43.93)
(4.13)
(4.13)
(3.80)
(0.47)
(1.88)
BCT-53
-4.77**
0.41
-0.85**
0.02**
-2.81**
4.03**
0.08**
-0.12**
0.25**
-0.03**
0.07**
(60.40)
(44.00)
(19.13)
(2.69)
(51.40)
(39.30)
(3.40)
(3.75)
(5.20)
(0.41)
(2.02)
BCT-110
5.12** 0.70* -0.10** 0.09** 2.41** -0.62** 0.11** 0.06** -0.20** -0.01** 0.07**
(80.57) (45.00) (16.30) (3.39) (55.27) (64.47) (4.41) (4.17) (3.50) (0.44) (3.52)
SE (gi) 0.05 0.34 0.03 0.003 0.05 0.11 0.004 0.004 0.04 0.004 0.004
Shende et al. (2012)
311
Next to CLN2498-D, significantly
positive GCA effects for seven
characters namely, plant height,
numbers of flower cluster plant-1,
numbers of fruit flower cluster-1,
numbers of fruit plant-1, TSS, fruit
acidity, and fruit yield plant-1 was
shown by CLN2762-A. Among the
testers, significant and positive GCA
effects had shown by BCT-110 for
six characters like plant height,
numbers of fruit flower cluster-1,
numbers of fruit plant-1, polar
diameter, equatorial diameter, and
fruit yield plant-1, while significant
GCA effects had shown by BCT-53
and DVRT-2 for five and four traits,
respectively. Negatively significant
GCA effects for days to 50%
flowering were displayed by
CLN2498-D and DVRT-2. The
highest per se performance for fruit
yield was shown by BCT-110, while
the lowest per se for days to 50 %
flowering was exhibited by DVRT-
2. While considering the traits (TSS
and acidity of fruit) suitable for
processing, two parents namely,
BCT-53 (5.20o brix and 0.41%) and
CLN2762-A (4.30o brix and 0.47%)
satisfied the requirements of quality
attributes for processing.
Heterobeltiosis and SCA
The per se performance of crosses,
per cent of heterobeltiosis, range of
heterobeltiosis and estimates of SCA
effects for eleven characters are
given in Table 4. The maximum
significant heterobeltiosis for plant
height was exhibited by CLN2762-A
× BCT-110 (5.63%) followed by
CLN2777-C × BCT-53 (4.34%) and
CLN-2762-A × DVRT-2 (4.19%).
Best hybrid for plant height as
derived from this investigation was
CLN-2762-A × BCT-110 (85.63cm)
showing a heterosis of 5.63% over
better parent.
Good cross showing
heterobeltiosis for days to 50%
flowering was CLN2498-D x
DVRT-2 (-3.22%). Selection of
hybrids showing negative heterosis
over their better parents for this
character may be useful for
developing early commercial
hybrids. The line DVRT-2 emerged
as the one of the earliest parents
(41.67 days). The best heterotic
cross CLN2498-D x DVRT-2 (40.33
days) showed negative heterosis of -
3.22% over better parent, providing
the best population for selecting
early plant type.
The maximum
heterobeltiosis for numbers of
flower cluster plant-1 was exhibited
in desired direction by CLN2498-D
× BCT-110 (34.15%) followed by
CLN2762-A × DVRT-2 (16.48%)
and CLN2498-D × DVRT-2
(15.71%). Best hybrid as derived
from this investigation was CLN-
2498D×BCT-110 (21.87
flowers/cluster) showing a heterosis
of 34.15% over better parent.
The maximum and
significant heterobeltiosis for
numbers of fruit flower cluster-1 was
exhibited by CLN2498-D × BCT-
110 (12.44%) followed by
CLN2762-A × BCT-110 (8.13%)
and CLN2498-D × BCT-53 (2.53%).
Best hybrid as derived from this
investigation was CLN2498-D ×
BCT-110 (3.86 fruits/cluster)
showing a heterosis of 12.44% over
better parent.
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
312
Table 4. Heterobeltiosis and estimates of SCA effects for eleven characters in
tomato hybrids.
Characters Better cross/crosses Heterobeltiosis
(%)
Range of
heterobeltiosis
Specific
combining ability
effects (per se
performance)
Plant height
(cm)
CLN-2762A×BCT-110
5.63**
-14.39 to 5.63
0.68** (85.63)
CLN-2777C×BCT-53
4.34**
2.48** (64.13)
CLN-2762A×DVRT-2
4.19**
4.99** (84.47)
Days to
50%
flowering
CLN-2498D×DVRT-2
-3.22**
-3.21 to 2.40
-0.07 (40.33)
Numbers of
flower
cluster
plant-1
CLN-2498D×BCT-110
34.15**
-17.44 to
34.15
2.50** (21.87)
CLN-2762A×DVRT-2
16.48**
1.65** (20.27)
CLN-2498D×DVRT-2
15.71**
0.12 * (20.13)
Numbers of
fruit flower
cluster-1
CLN-2498D×BCT-110
12.44**
-12.77 to 12.44
0.18** (3.86)
CLN-2762A×BCT-110
8.13**
0.17** (3.81)
CLN-2498D×BCT-53
2.53**
-0.09** (3.52)
Numbers of
fruit plant-1
CLN-2498D×BCT-110
52.59**
-15.98 to 52.59
12.56** (84.33)
CLN-2762A×DVRT-2
51.98**
4.08** (67.33)
CLN-2498D×DVRT-2 33.62** -1.53** (68.23)
Fruit
weight (g)
CLN-2777C×BCT-53
3.12**
-25.29 to
3.12
-2.32** (46.33)
CLN-2498D×BCT-53
0.98**
2.74** (65.40)
Polar
diameter
(cm)
CLN-2498D×BCT-53
21.76**
-12.45 to
21.76
-0.56** (5.26)
CLN-2777C×BCT-110
3.33**
0.40** (4.55)
CLN-2498D×DVRT-2 2.62** -0.01 (4.43)
Shende et al. (2012)
313
Table 4. (cont’d)
Characters Better cross/crosses Heterobeltiosis
(%)
Range of
heterobeltiosis
Specific
combining ability
effects (per se
performance)
Equatorial
diameter
(cm)
CLN-2777C×BCT-110
15.84**
-8.88 to 15.84
0.60** (4.83)
CLN-2498D×DVRT-2
6.30**
0.20** (5.06)
CLN-2498D×BCT-53
2.45**
0.20** (4.88)
TSS (o brix)
CLN-2762A×DVRT-2
31.01**
-20.51 to
31.01
0.57** (5.63)
CLN-2498D×BCT-110
20.00**
0.36** (4.20)
CLN-2777C×BCT-110
8.57**
0.15* (3.80)
Titratable
acidity (%)
CLN-2762A×DVRT-2
17.02**
-3.57 to 17.02
0.02** (0.55)
CLN-2498D×DVRT-2
13.48**
0.01 (0.53)
CLN-2498D×BCT-110
12.12**
0.02** (0.49)
Fruit yield
plant-1 (kg)
CLN-2777C×BCT-53
38.78**
-33.33 to
38.78
0.40** (2.80)
CLN-2498D×DVRT-2
23.50**
0.26** (4.12)
CLN-2498D×BCT-110
20.17**
0.17** (4.23)
*, ** Significant at P <0.05 and 0.01, respectively
The range of heterosis for numbers
of fruit plant-1 varied between -
15.98% and 52.59% over better
parent. The maximum significant
heterobeltiosis was exhibited by
CLN2498-D × BCT-110 (52.59%)
followed by CLN2762-A × DVRT-2
(51.98%) and CLN2498-D ×
DVRT-2 (33.62%). Best hybrid as
derived from this investigation was
CLN2498-D × BCT-110 (84.33
fruits per plant) showing a heterosis
of 52.59% over better parent. Better
crosses showing heterobeltiosis for
fruit weight were CLN2777-C x
BCT-53 (3.12%) followed by
CLN2498-D x BCT-53 (0.98%).
Best hybrid for fruit weight on the
basis of per se performance was
CLN2498-D x BCT-53 (65.40 g)
showing 0.98% heterosis over better
parent. Best parent was CLN2498-D
(64.77g), which has been utilized to
develop best hybrid and some other
good crosses.
The maximum significant
heterobeltiosis for polar diameter of
fruit was exhibited by CLN2498-D x
BCT-53 (21.76%) followed by
CLN2777-C x BCT-110 (3.33%)
and CLN2498-D x DVRT-2
(2.62%). Best hybrid as derived
from this investigation was
CLN2498-D x BCT-53 (5.26 cm)
showing a heterosis of 21.76% over
better parent.
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
314
Equatorial diameter of fruit
is a character related with size of the
fruit and the desirable heterosis is a
positive one. Good crosses for this
character were CLN2777C x BCT-
110 (15.84%) followed by
CLN2498-D x DVRT-2 (6.30%) and
CLN2498-D x BCT-53 (2.45%).
Best hybrid for this character as
derived from this investigation was
CLN2498-D x DVRT-2 (5.06 cm)
showing a heterosis of 6.30 % over
better parent.
The range of heterosis for
total soluble solids (TSS) was from -
20.51% to 31.01% over better
parent. Good crosses showing
heterobeltiosis for this character
were CLN2762-A x DVRT-2
(31.01%), CLN2498-D x BCT-110
(20.00%) and CLN2777-C x BCT-
110 (8.57%). Best hybrid for TSS
was CLN2762-A x DVRT-2 (5.63°
brix) with a heterosis of 31.01%
over better parent. Best parent on the
basis of mean performance was
BCT-53 (5.20° brix) as presented in
Table 3.
The maximum significant
and positive heterosis for fruit
acidity over better parent was shown
by CLN2762-A x DVRT-2
(17.02%) followed by CLN2498-D
x DVRT-2 (13.48%) and CLN2498-
D x BCT-110 (12.12%). Best hybrid
for fruit acidity was CLN2762-A x
DVRT-2 (0.55%) having 17.02%
heterosis over better parent. On the
basis of mean value, DVRT-2 and
CLN2762-A (0.47%) were selected
as most promising parents as
presented in Table 3.
The range of heterosis for
fruit yield plant-1 was from -33.33%
to 38.78% over better parent. Good
crosses showing heterobeltiosis for
this character were CLN2777-C x
BCT-53 (38.78%), CLN2498-D x
DVRT-2 (23.50%) and CLN2498-D
x BCT-110 (20.17%). Best hybrid
was CLN2498-D x BCT-110 (4.23
kg per plant) with a heterosis of
20.17% over better parent. Best
parent on the basis of mean
performance was BCT-110 (3.52 kg)
as reflected in Table 3.
Specific combining ability
effects represents dominance and
epistatic components of genetic
variation which are not fixable but
the crosses with high SCA effects
involving good general combiner
parents can be exploited in future
heterosis breeding program.
None of the crosses showed
negative significant superiority for
days to 50 % flowering. Out of the 9
crosses, 5 hybrids each showed
significant SCA effects for plant
height, number of flower clusters
plant-1, equatorial diameter and fruit
yield plant-1 in the desired direction.
Four hybrids each showed
significant SCA effects for numbers
of fruit cluster-1 and fruit weight.
Three hybrids each exhibited
significant SCA effects for numbers
of fruit plant-1, TSS and fruit acidity.
The cross CLN2498-D x BCT-110
showed significant positive SCA
effects for numbers of flower cluster
plant-1, numbers of fruit cluster-1,
numbers of fruit plant-1, TSS, fruit
acidity and fruit yield plant-1 and
non-significant negative SCA effects
for days to 50% flowering and it was
3rd highest for yield plant-1 in respect
to SCA effects coupled with the
highest per se performance. The
cross CLN2777-C x BCT-53 also
showed significantly positive SCA
effects for plant height, numbers of
flower cluster plant-1, numbers of
fruit flower cluster-1, numbers of
fruit plant-1, fruit acidity, fruit yield
plant-1 and negative SCA effects for
Shende et al. (2012)
315
days to 50% flowering and it was
highest for yield plant-1 in respect to
SCA effects coupled with high per
se performance. Cross CLN2498-D
x DVRT-2 also showed significantly
positive SCA effects for numbers of
flower cluster plant-1, fruit weight,
equatorial diameter and fruit yield
plant-1 and negative SCA effects for
days to 50% flowering and it was
second highest for yield plant-1 in
respect to SCA effects coupled with
high per se performance. The cross
CLN2762-A x DVRT-2 also showed
significant SCA effects for fruit
yield plant-1 and other component
characters in the desired direction
with high per se performance.
DISCUSSION
While studying the nature of gene
action governing eleven traits, it has
been observed that overwhelming
non-additive gene action is
responsible for the control of all the
traits studied except TSS content of
fruit for which preponderance of
both additive and non-additive gene
actions was evident. The response of
non-additive gene action for the
conditioning of plant height, days to
50% flowering and fruit weight
(Ahmad et al., 2009); number of
flower cluster plant-1 (Bhatt et al.,
2001); number of fruits flower
cluster-1 (Bhatt et al., 2001; Makesh
et al., 2002), number of fruits plant-1
(Garg et al., 2007; Ahmad et al.,
2009); acidity (Garg et al., 2007;
Virupannavar et al., 2010), and fruit
yield plant-1 (Mahendrakar et al.,
2005; Garg et al., 2007; Singh et al.,
2010) have been reported
irrespective of the parental materials
used, methods followed and
environments in which experiments
conducted. The successful breeding
methods will be those that
accumulate the genes to form
superior gene constellations
interacting in a favorable manner.
These findings suggested heterosis
breeding as the best possible option
for improving the above traits of
tomato. The response of both
additive and non-additive gene
actions for the control of TSS
content of fruit has also been
reported (Rai et al., 2005; Sharma et
al., 2006). In this case use of a
population improvement method in
the form of diallel selective mating
(Jensen, 1970) or mass selection
with concurrent random mating
(Redden and Jensen, 1974) might
lead to release of new varieties with
higher TSS in tomato.
Restricted recurrent
selection by inter-mating the most
desirable segregants followed by
selection might also be a useful
breeding strategy for the exploitation
of both additive and non-additive
types of gene action. On the contrary
to this study, some researchers
(Makesh et al., 2002; Cheema et al.,
2003; Brar et al., 2005; Rai et al.,
2005; Sharma et al., 2006; Saidi et
al., 2008; Mondal et al., 2009) while
examining genetic control of days to
50% flowering, plant height,
numbers of fruit flower cluster-1,
acidity, polar diameter, equatorial
diameter, and fruit yield plant-1
found both additive and non-additive
gene effects to be involved. On the
other hand, Garg et al. (2007) and
Mondal et al. (2009) reported the
importance of non-additive genetic
effects for TSS content of fruit.
Some differences in interpretation in
the present study might have arisen
from difference in genotype used
and environment under which the
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
316
trial was conducted because
estimates of gene effects are proved
to change with environment and
genotypes.
When the parents were
assessed for their general combining
ability for eleven traits, two lines
‘CLN2498-D’ and ‘CLN2762-A‘
were identified as good combiners
for both yield and processing quality
related traits and the tester ‘BCT-
110’ was selected as good combiner
for yield and its component
characters. Since high gca effect is
related to additive and additive ×
additive interaction and represents
the fixable components of genetic
variance, ‘CLN2498-D’, ‘CLN2762-
A’ and ‘BCT-110’ could be used
effectively in tomato breeding for
high yield and better processing
quality. Significant negative GCA
effects of days to 50% flowering for
the line ‘CLN2498-D’ and for the
tester ‘DVRT-2’ indicating these
line and tester have additive genetic
effects resulting in lower value for
this trait. In earlier study Ahmad et
al. (2009) reported significant
negative GCA effects for days to
50% flowering in tomato.
Out of nine cross
combinations, four crosses for plant
height, one cross for days to 50%
flowering, three crosses for numbers
of flower cluster plant-1, four crosses
for numbers of fruit flower cluster-1,
eight crosses for numbers of fruit
plant-1, two crosses for fruit weight,
four crosses for polar diameter, three
crosses for equatorial diameter, five
crosses for TSS, six crosses for fruit
acidity, and six crosses for fruit
yield plant-1 exhibited significant
heterobeltiosis in desired direction.
According to Jinks (1983), the
prerequisite for a high, uniform, and
stable heterotic effect is the correct
gene content, which can be
assembled in the homozygous state
or if the appropriate alleles are
completely dominant as a
heterozygote without affecting
performance. All crosses except one
(CLN2777-C x BCT-110) produced
negative or low positive
heterobeltiosis for equatorial
diameter of fruit. This indicates that
high-performing parents having poor
gca may not produce highly
heterotic crosses. It may be
concluded that a superior
performance of the hybrids for
equatorial diameter of fruit depends
on the gca of the parents involved.
Positive and significant heterosis
over better parent for plant height
(Prashant, 2004; Tiwari and Lal,
2004; Ashwini and Vidyasagar,
2005); numbers of flower cluster
plant-1 (Prashant, 2004; Tiwari and
Lal, 2004; Ashwini and Vidyasagar,
2005); numbers of fruit flower
cluster-1 (Harer et al., 2006; Gul et
al., 2010); numbers of fruit plant-1
(Thakur et al., 2004; Tiwari and Lal,
2004; Gul et al., 2010); fruit weight
(Tiwari and Lal, 2004); polar and
equatorial diameter (Sharma et al.,
2001); TSS content (Shrivastava,
1998; Bhatt et al., 2001); fruit
acidity (Makesh et al., 2002); and
fruit yield plant-1 (Bhutani et al.,
1973; Kanthaswamy and
Balakrishnan, 1989; Yadav et al.,
1989; Bhatt et al., 1999;
Nagaraj,1995; Tiwari and Lal, 2004)
have been reported with dissimilar
parents and environments.
The perusal of analyses
revealed that the cross combinations
which showed maximum significant
heterobeltiosis for fruit yield plant-1
also exhibited heterosis over better
parent for numbers of fruit plant-1.
Therefore, it appeared that heterosis
Shende et al. (2012)
317
for fruit yield per plant could be
ascribed mainly to heterosis
observed for numbers of fruit plant-1.
There was a reasonable ground to
suggest that the heterotic expression
for fruit yield plant-1 in cross
combination CLN2498-D x BCT-
110 was due to additive and additive
x additive type of gene effects as the
cross combination involved parents
with best general combining ability.
Progress in improving the desired
trait will be slow if the parental
selection is based on per se
performance alone. Absence of
significant heterosis in most crosses
could be explained by the internal
cancellation of heterosis
components.
Normally sca effects do not
contribute much to improvement of
self-pollinated crop like tomato.
However, crosses showing desirable
specific, along with good general
combining ability could be utilized
in breeding programs. Such
programs would be more effective if
two of the parents are a good
combiner or any one of them is a
poor combiner. In the present study,
two crosses namely, CLN2777-C x
BCT-53 and CLN2498-D x DVRT-2
were identified as good specific
combiners for their high SCA effects
for fruit yield plant-1 and other
contributing characters and the cross
CLN2498-D x BCT-110 was
selected for high SCA effects for
TSS and acidity content of fruit
along with fruit yield. One parent
involved in these combinations had
a high gca effect and high per se
performance for several characters.
Therefore, parents with High × High
or High × Poor gca effects could
produce desirable transgressive
segregants in advance generations
because additive gene effects present
in the good combiner and
complementary epistatic effects in
the F1 may act in the same direction
to maximize desirable plant
attributes.
CONCLUSIONS
The present study found the
importance of non-additive gene
effects in governing fruit yield and
most of the yield attributes in
tomato. However, both additive and
non-additive gene effects to be
involved for control of TSS content
of fruit. Among the lines,
‘CLN2498-D’ and ‘CLN2762-
A’were identified as most promising
combiners for fruit yield along with
good processing traits. Among the
testers, ‘BCT-110’ was found to be
the best general combiners for fruit
yield and its component characters.
These three parental materials could
be used further in tomato
hybridization programs. Results of
the crosses of CLN2777-C x BCT-
53 and CLN2498-D x DVRT-2
could be exploited commercially
because of high fruit yield and the
cross CLN2498-D x BCT-110 could
be utilized for better processing
qualities.
ACKNOWLEDGEMENTS
Authors are grateful to Asian Vegetable
Research and Development Centre, Taiwan
and Professor Pranab Hazra, Department of
Vegetable Crops, BCKV, West Bengal,
India for providing genetic materials to
conduct this study.
SABRAO J. Breed. Genet. 44 (2) 302-321, 2012
318
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