Brassica

International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 7
143701-5858- IJBAS-IJENS @ February 2014 IJENS I J E N S
Combining Ability and Heritability Studies for
Important Traits in F2 of Brassica Napus
*Ali Muhammad, Raziuddin, Ashiq Muhammad, Haneef Raza, Aziz Ur Rahman and Imtiaz Ali
*Author for Correspondence: alikhaksar87@gmail.com
Department of Plant Breeding and Genetics
The University of Agriculture, Peshawar-Pakistan
Abstract-- The present study was undertaken to estimate
combining ability and heritability in 4 × 4 diallel crosses of
Brassica napus L. at the University of Agriculture, Peshawar
during 2012-13 crop season. The genetic material comprised
four parental genotypes along with their 12 F2 populations grown
in randomized complete block design with three replications.
Analysis of variance revealed significant (P≤0.01) differences for
plant height, main raceme length, pod length, while significant
(P≤0.05) differences were observed for days to 50% flowering.
Parental genotype G6 was the best general combiner for days to
50% flowering, plant height, pod length. G9 had the highest
GCA for main raceme length. Cross “G2 × G4” was the best
specific combiner for plant height, pod length. For reciprocal
effects cross “G6 × G4” was a good combination with highest
reciprocal effects for main raceme length. Broad sense
heritability recorded was 0.26, 0.52, 0.65 and 0.73 for days to
50% flowering, main raceme length, plant height and pod length
respectively, suggesting the effectiveness of selection of these
traits in different generations. The overall study showed the
importance of both additive and non-additive gene actions.
Index Term- Brassica napus, combining ability, GCA, SCA,
RCA, heritability and F2 population
INTRODUCTION
Brassica napus is the major crop of genus Brassica and
family Brassicaceae or cruciferae. It is commonly known as
rapeseed, oilseed rape or canola is used as major vegetable
oil source. Brassica seed oil is considered as the major
source of edible oil in Indo-Pak subcontinent Pakistan. At
present, total edible oil requirement in the country is 3.079
million tons of which 0.696 million tons contributed by
local production (34 percent of the requirement); while
remaining requirement was met through import of 2.383
million ton. The import bill cost Rs. 224 billion (US$ 2.611
billion) in 2010-11 (PBS, 2012). In Pakistan, during 2010-
2011, brassica was planted on 575 thousand acres which
produced 203 thousand tons seed with oil production of 61
thousand tons (PBS, 2012).
In rapeseed breeding program for hybrid and open
pollinated varieties, general and specific combining ability
effects (GCA and SCA) are important indicators of the
potential of inbred lines in hybrid combinations. To
incorporate desirable characters to maximize economic
yields, the knowledge of combining ability is valuable to get
information on selection of parents and nature of gene
actions involved. This important information could provide
an essential tool for the rapeseed breeders in the selection of
better parental combination for further improvement (Sher
Aslam Khan et al, 2009; Panhawar et al, 2008). General
combining ability is used to specify the average
performance of a line in hybrid combination. Specific
combining ability is used to indicate those cases in which
certain combinations do relatively better or worse than
would be expected on the basis of the average performance
of the lines involved (Sprague and Tatum 1942). Most of
the quantitative characters are controlled by polygene,
which are influenced by the environment. Hence, it is
essential to partition the overall variability into heritable and
non-heritable components with the help of heritability. The
objectives of the present study were to identify good
combiners for future breeding and to estimate heritability
for various traits in segregating generations of Brassica
napus.
MATERIALS AND METHODS
This experiment was conducted to determine combining
ability and heritability for important traits in F2 populations
of Brassica napus L. at the research farm of Department of
Plant Breeding and Genetics, The University of Agriculture,
Peshawar during 2012-13. Genetic material comprised a set
of four Brassica napus L. genotypes viz., G2, G4, G6, G9
and their 12 F2 populations (G2 × G4, G2 × G6, G2 × G9,
G4 × G2, G4 × G6, G4 × G9, G6 × G2, G6 × G4, G6 × G9,
G9 × G2, G9 × G4, G9 × G6). The parental genotypes were
provided by China and their F1 populations were developed
in The University of Agriculture, Peshawar in 2011-12.

Table I
List of genotypes used in the study
Genotypes Codes Source
G2 DH-1136-4-4
G4 DH-1136-1-117
G6 DH-1147-2-26
G9 DH-1209-15-67
All the parental genotypes along with their F2 populations
were sown in randomized complete block design with three
replications. Row to row distance was 60 cm while plant to
plant distance was 20 cm and row length was 4 m. Data
were recorded on the following parameters on 15 randomly
selected plants in each genotype for days to 50% flowering,
plant height, main raceme length and pod length.
Statistical analysis
Analysis of variance
The data taken were statistically analyzed according to the
appropriate method suggested for randomized complete
block design (Steel and Tori, 1980), while mean separation
was carried out through LSD test at 5% level of probability.
The variance due to crosses will be partitioned into the
variance due to general combining ability effects, specific
combining ability effects and reciprocal effects by the
following formula for Method I of model I (Griffing’s,
1956).
General combining ability (GCA)
Y..
n
1
-i)Y+.Y(
2n
1
=g 2.ii
Specific combining ability (SCA)
Y..
n
1
+j)Y+.Y+iY+.Y(
2n
1
-)Y+Y(
2
1
=s 2.j.ijiijij
Reciprocal effects (REC)
)Y-Y(
2
1
=r jiijij
Heritability (B.S)
Variances components and heritability estimates were
calculated by the following formula suggested by Singh and
Chowdhury (1985);
p
g
BS =h 2
2
)(
2


g
2
 = Genotypic variance for a trait.
p
2
 = Phenotypic variance for a trait.
h2
(BS) = Broad sense heritability for a trait.
RESULTS AND DISCUSSION
Days to 50% flowering
In brassica early flowering results in comparatively larger
grain filling period, which finally results into bold grains
hence negative GCA and SCA effects are preferred.
The mean squares showed that the effects due to SCA were
significant (P≤0.05) while non-significant (P>0.05)
differences were observed for GCA and RCA (Table II).
These results revealed the presence of non-additive gene
actions in the expression of days to 50% flowering. Non-
significant RCA indicated the absence of cytoplasmic genes
contributed by the female parents. Among parents G2 was
the best general combiner as it indicated the desired
minimum GCA (-0.78) for days to 50% flowering followed
by G6 (-0.16) as presented in the Table III.
Among the F2 populations, G4 × G9 and G6 × G9 were the
best specific combinations, as it revealed the desired
minimum SCA (-2.17) followed by G2 × G6 (-1.58) as
shown in the Table IV. The desired minimum reciprocal
effect was indicated by the cross G9 × G6 (-0.62) followed
by G9 × G2 (-0.1) as showed in the Table V. Our results
suggested the presence of both types of gene action for days
to 50% flowering. Huang et al. (2009) and Oghan et al.
(2009) also reported significant GCA and SCA effects in
Brassica napus. Recently, Maurya et al. (2012) also
reported similar results in Brassica juncea.
Genetic and environmental variances for days to 50%
flowering were 4.66 and 13.08 respectively, while
heritability (bs) was 0.26 (Table VI). Marjanovic et al.
(2011) also reported low heritability for days to 50%
flowering in Brassica napus. Similarly, Oghan et al. (2009)
reported high heritability for days to 50% flowering in
Brassica napus L. while Patel and Vyas (2011) reported
moderate to high heritability for days to 50% flowering in
Brassica juncea L..
Plant height (cm)
As shown in the Table II, both GCA and SCA effects were
highly significant (P≤0.01), while RCA showed non-
significant (P>0.05) differences. Non-significant RCA
effects indicated the absence of cytoplasmic genes given by
the female parents. Taller plants mostly face the problem of
lodging therefore short stature plants were appropriate in
brassica hence negative GCA and SCA were preferred.
Among parental genotypes, G2 indicated the desired

minimum GCA (-4.98) and was the best general combiner
for plant height tracked by G4 (-1.92) as indicated in the
Table III. Our results are further strengthened by Rameeh
(2012) who reported the presence of both additive and non-
additive gene actions in the appearance of plant height
showing that selection would bring about significant
improvement in Brassica napus L..
G2 × G9 was proved as the best specific combiner among
the F2 populations, as it acquired the desired minimum SCA
(-1.51) as presented in the Table IV. The desired minimum
reciprocal effect was indicated by the combination G9 × G2
(-0.88), as observed in Table V. The present findings are in
agreement with the findings of Akbar et al. (2008) and
Azizinia (2011) they found significant GCA and SCA
effects for plant height and revealed the importance of both
types of gene actions in Brassica napus L.. Dar et al. (2013)
observed significant GCA effects in Brassica rapa L.
indicated the presence of additive gene action for plant
height. Rameeh (2011) found significant SCA effects for
plant height showed the presence of non-additive gene
action in Brassica napus L..
Genetic and environmental variances for plant height were
97.68 and 53.5 respectively, while heritability (bs) was high
as 0.65 (Table VI). Our results are in agreement with the
findings of Shehzad and Farhatullah (2012). They found
high heritability in F2 population of Brassica napus. High
heritability estimates have also been reported earlier by
Mahak et al. (2011) in Indian mustard. However, Ali et al.
(2002) and Ali et al. (2003) reported low broad sense
heritability for plant height in Brassica napus L..
Main raceme length (cm)
Combining ability analysis showed highly significant
(P≤0.01) differences for GCA and SCA (Table II). Among
Parents, G9 acquired maximum GCA (2.58) and was
considered the best general combiner for main raceme
length followed by G6 (1.95), as indicated in the Table III.
Similar results were also reported by Singh et al. (2011) in
Indian mustard (Brassica juncea) and found significant
GCA and SCA effects for main raceme length. These
outcomes proposed that both additive and non-additive gene
actions were complicated in controlling main raceme length.
Among the F2 descendants, G2 × G6 was the best specific
combiner, as it exhibited the maximum SCA (3.9) followed
by G4 × G6 (2.25), as showed in the Table IV. The maternal
effects were non-significant (P>0.05) for main raceme
length due to the lack of cytoplasmic genes given by the
female parents. Cross combination G6 × G4 exhibited the
desire maximum RCA (5.3) followed by G4 × G2 (2.1) and
G9 × G6 (0.85), as indicated in the Table V. Similar results
were earlier reported by Gupta et al. (2011) and Singh et al.
(2010) they found significant GCA and SCA effects for
main raceme length in Brassica juncea.
Genetic and environmental variances for main raceme
length were 22.35 and 20.91 respectively, while heritability
(bs) was 0.52 (Table VI). Nasim et al. (2013) reported low
heritability for main raceme length in Brassica napus L. Ali
et al. (2013) reported high heritability for main raceme
length in Brassica carinata.
Pod length (cm)
Combining ability analysis showed highly significant
(P≤0.01) differences for GCA and SCA (Table II). These
results proposed that both additive and non-additive gene
actions were complicated in controlling pod length. Parent
G6 acquired maximum GCA (0.89) and was considered the
best general combiner for pod length, as indicated in the
Table III.
Among the F2 populations G4 × G6 was the best specific
combiner, as it indicated the maximum SCA (0.93)
followed by G2 × G6 (0.57), as showed in the Table IV. The
maternal effects were also highly significant for pod length.
Cross combination G9 × G6 obtained the desire maximum
RCA (0.67) followed by G4 × G2 (0.33), as indicated in the
Table V. The maximum reciprocal effects showed by these
cross combinations for pod length were because of
cytoplasmic genes donated by the female parents. Our
results are in agreement to the earlier findings of Rameeh
(2010) in Brassica napus L. who found significant GCA
and SCA effects for pod length and revealed the importance
of both types of gene actions. Similarly, Maurya et al.
(2012) found significant GCA effects in Brassica juncea
showed the presence of additive gene action for pod length.
Sabaghnia et al. (2010) reported significant SCA effects for
pod length in rapeseed and Arifullah et al. (2011) reported
significant SCA effects in Brassica juncea L. indicated the
presence of non-additive gene action for pod length.
Genetic and environmental variances for pod length were
1.21 and 0.44, respectively. The estimated heritability (bs)
was high i.e. 0.73 (Table VI). Chaghakaboodi et al. (2012)
also reported high heritability in Brassica napus L.
However, Aytac and Kinaci (2009) and Zare and
Sharafzadeh (2012) found low broad sense heritability for
pod length in rapeseed (Brassica napus L.).

Table II
Mean squares for ANOVA and combining ability for various important traits in a 4×4 diallel cross of Brassica napus conducted at The University of Agriculture,
Peshawar during 2012-13
Parameters
ANOVA COMBINING ABILITY
GMS EMS CV% GCA SCA RCA
Days to 50% flowering 27.07* 13.08 4.06 2.95ns
12.46* 8.63ns
Plant height 346.56** 53.5 5.32 171.20** 165.85** 37.35ns
Main raceme length 87.96** 20.91 8.92 60.49** 28.93** 14.12 ns
Pod length 4.08** 0.44 11.88 2.90** 1.11** 0.71**
** Significant at P≤0.01, * significant at P≤0.05 and ns = Non significant
Table III
Estimates of GCA effects for various important traits in a 4×4 diallel cross of Brassica napus conducted at The University of Agriculture, Peshawar during 2012-
13
Parameter G2 G4 G6 G9
Days to 50% flowering -0.78 0.33 -0.15 0.6
Plant height -4.98 -1.92 5.89 1.0
Main raceme length -1.28 -3.25 1.95 2.58
Pod length -0.41 -0.33 0.89 -0.15
Table IV
Estimates of SCA effects for various important traits in a 4×4 diallel cross of Brassica napus conducted at The University of Agriculture, Peshawar during 2012-
13
Parameters G2×G4 G2×G6 G2×G9 G4×G6 G4×G9 G6×G9
Days to 50% flowering 3.24 -1.58 2.7 -0.27 -2.17 -2.17
Plant height 9.76 5.13 -1.51 5.39 4.65 4.65
Main raceme length -0.08 3.9 -3.3 2.25 -3.4 -3.4
Pod length -0.53 0.57 -0.51 0.93 0.13 0.13
Table V
Estimates of RCA effects for various important traits in a 4×4 diallel cross of Brassica napus conducted at The University of Agriculture, Peshawar during 2012-
13
Parameters G4×G2 G6×G2 G6×G4 G9×G2 G9×G4 G9×G6
Days to 50% flowering -0.53 3.38 2.05 -0.1 3.1 -0.62
Plant height 5.4 0.52 5.4 -0.88 1.14 7.17
Main raceme length 2.1 -1.39 5.3 -1.88 -1.92 0.85
Pod length 0.33 -0.98 0.13 0.15 -0.76 0.67
Table VI
Variance components and heritability(BS) for various important traits in a 4×4 diallel cross of Brassica napus conducted at The University of Agriculture, Peshawar
during 2012-13
Parameters Vg Ve Vp h2
(bs)
Days to 50% flowering 4.66 13.08 17.74 0.26
Plant height 97.68 53.5 151.18 0.65
Main raceme length 22.35 20.91 43.26 0.52
Pod length 1.21 0.44 1.65 0.73

CONCLUSIONS AND RECOMMENDATIONS
From the present research work “to estimate combining
ability and heritability in Brassica napus L. genotypes”
the following conclusions have been derived;
Analysis of variance showed significant differences for
the genotypes. Parental genotypes G6 and G9 were best
general combiners whereas cross combinations G2 × G4
and G6 × G4 were best specific and reciprocal
combinations, respectively therefore could be used in
future breeding program. Plant height and main raceme
length were high heritable traits and have the room for
further improvement in the future breeding programs. The
overall study discloses the prominence of both additive
and non-additive genetic variability suggesting the use of
integrated breeding strategies which can efficiently
exploit the additive as well as non-additive genetic
effects.
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