Exploitation of heterosis and combining ability for earliness and vegetative traits in ridge gourd
which 8 were in desirable negative direction. The
sca effects, showed high amount of heterosis for
range varied between -4.16 (PCPGR 7256 X PRG
various characters. In many of these hybrids, non
142) and 4.54 (PCPGR 7256 X PRG 137). The highest
additive gene action was involved for almost all the
negative significant sca effect was recorded for cross
characters. These results are in conformity with the
PCPGR 7256 X PRG 142 (-4.16) followed by PRG 117
results reported by Sirohi and Choudhary (1978)
X PRG 131 (-3.20) and PRG 117 X PRG 137 (-2.60.
in bitter gourd. In ridge gourd, Shaha and Kale
Regarding days taken to first fruit harvesting among
(2003) found significant high sca effect for most of
28 crosses, 11 showed significant sca effects in which
the characters in several cross combinations. The
8 were in desirable negative direction and 3 in
results of the present study are in agreement with
positive direction. The highest effects were recorded
findings reported by Rao et al. , (2000b), who reported
by cross PRG 131 X PRG 132 (-3.06) followed by
that the components of variance for sca were higher
PRG 142 X PRG 131 (-2.50) and PRG 142 X PRG 132
than those of gca for most of the characters. In the
(-2.46). 22 crosses expressed significant sca effects for
present study, the extent of heterosis was studied in
vine length in which 10 were in positive direction.
28 F1 hybrids of ridge gourd developed by 8 parents
The highest effect was shown by PCPGR 7256 X
in diallel design in open field. There was a wide
PRG 117 (1.54) followed by PCPGR 7256 X PRG 131
variation in magnitude and direction of heterosis for
(1.03), PRG 137 X PRG 7 (1.03) and PRG 117 X PRG
all characters (Table 4). For the development of early
120 (0.79). In case of number of primary branches
fruiting genotypes, negative heterosis is desirable
PRG 132 X PRG 120 (1.86) showed highest sca effect
for days to first female flower, node number to first
followed by PCPGR 7256 X PRG 142 (1.02). PRG 131
female flower and days taken to Ist fruit harvesting.
X PRG 132 (0.79) showed third highest effect.
The magnitude of heterobeltiosis for days to first
Total 13 crosses exhibited the significant sca effect.
female flower ranged from -17.97% (PRG 117 X PRG
Specific combining ability effect (SCA) which
131) to 8.73% (PCPGR 7256 X PRG 142). 19 crosses
represents the predominance of nonadditive gene
showed significant heterobeltiosis out of which 17
action is a major component that may be utilized in
exhibited negative heterosis over better parent.
heterosis breeding. The significance of SCA effect
The maximum heterobeltiosis was found in PRG 117
elucidates the presence of genetic diversity among
X PRG 131 (-17.97%) followed by PRG 131 X PRG
parents tested and illustrates the contribution of
132 (-17.19%) and PRG 142 X PRG 131 (-16.41%).
dominance and/ or epistatic effect which represent
The magnitude of standard heterosis for that trait
the non fixable components of the genetic variation
ranged from -11.40% (PRG 117 X PRG 142) to 20.18%
related to heterosis. Specific combining ability effects
(PCPGR 7256 X PRG 142). For check parent 15 crosses
mainly represent dominance, additive x dominance
showed significant heterosis in which 11 recorded
and dominance x dominance type of gene action. The
negative heterosis over check parent. The maximum
crosses showing sca effects involving parent with
standard heterosis was found for the cross PRG 117
good gca could be exploited as F1 hybrid breeding.
X PRG 142 (-11.40%) followed by PRG 117 X PRG 137
however, if a cross having high sca has one of its
(-8.77%), PRG 117 X PRG 132 (-8.77%) and PRG 117
parent as good general combiner and other as poor or
X PRG 131 (-7.89%), PRG 117 X PRG 120 (-7.89%).
averagecombiner,suchcrossesarelikelytogivesome
The magnitude of heterobeltiosis for node number
segregants, only if additive genetic system is present
to first female flower ranged from -59.26% (PCPGR
in a good general combiner and epistatic effects in the
7256 X PRG 142) to 56.00% (PCPGR 7256 X PRG 137).
cross act in the same direction so as to maximize the
21 crosses showed significant heterobeltiosis out of
desirable expression of the character in consideration
which 19 exhibited negative heterosis over better
(Whitehouse et al. , 1958, Lonnquist and Gardner
parent. The maximum heterobeltiosis was found
1961). Maximum F1 hybrids exhibiting significant
in PCPGR 7256 X PRG 142 (-59.26%) followed by
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