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Triticeae Genomics and Genetics 2014, Vol.5, No.2, 1-11
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2
(1989). But according to Fabrizius et al., (1998) more
the genetic dissimilarities among parents more will be
heterosis for yield in a hybrid. Similarly Singh et al.,
(2004), recommended that heterobeltiosis can be
valuable for decisive true heterotic cross combinations.
The researchers like Chowdhry et al (2001) reported
significant positive heterosis for peduncle length. Both
positive and significant negative heterosis and
heterobeltiosis for tillers per plant, plant height,
peduncle length, 100 grain weight and grain yield was
found in the studies of Farooq et al 2004.
The experiment was carried out aiming to study some
yield contributing traits in wheat hybrids under normal
and heat stress conditions.
1 Results
1.1 Genotypic differences among the parents
Analysis of variance indicated significant differences
(P<0.01) for all the traits among 49 genotypes under
both regimes. The mean squares for the traits are
represented in Table 1 describing high significance of
the ‘F’ test for all the traits under study.
Table 1 Mean squares of various plant traits in a 7×7 diallel cross under normal and heat stress conditions of
Triticum aestivum
L.
Source (Normal)
DF
Plant height Peduncle length Tillers per plant
100-grain weight
Grain yield per plant
Replication
2
11.57*
5.19
NS
0.63
NS
0.019
NS
1.44
NS
Genotypes
48
10.53**
7.84**
1.45**
0.12**
10.65**
Error
96
2.82
2.73
0.26
0.03
1.37
Mean
91.42
20.29
7.11
4.43
18.64
CV %
3.73
8.15
7.16
4.14
6.28
Source (H.Stress)
DF
Plant height Peduncle length Tillers per plant
100-grain weight
Grain yield per plant
Replication
2
6.054
NS
2.70
NS
0.046
NS
0.035
NS
0.174
NS
Genotypes
48
19.99**
7.45**
0.893**
0.515**
3.057**
Error
96
2.96
1.10
0.231
0.045
0.156
Mean
61.95
12.53
3.71
3.07
5.63
CV %
2.78
8.37
12.97
6.92
7.03
1.2 Heterosis for plant height under normal and
heat stress conditions
Plant height is among one of the most important
characters in wheat production. For this trait reduced
plant height is desirable because of the reason that
short stature varieties are more responsive to fertilizes
than the taller ones. Heterosis studies under normal
conditions for plant height revealed that 21 cross
combinations showed positive heterosis. Nine of the
crosses were highly significant and 2 crosses were
significant while remaining 10 crosses were
non-significant. Among crosses showing negative
values 5 crosses were highly significant, 3 were
significant and 13 were negative and non-significant
Table 2. Maximum positive heterosis was shown by
the cross Maya/Pavon × Shalimar-88 with a value of
(8.30%), followed by Shalimar-88×Maya/Pavon
(7.76%) and hybrid Punjab-85 × Maya/Pavon (5.57%).
Maximum negative heterosis was shown by the cross
combination Weebli-1×Uqab-2000 (-3.60%) followed
by Inqilab-91×Shalimar-88 (-3.30%).Under heat stress
conditions 30 crosses showed reduction in plant height.
Out of these 30 crosses 16 showed negative and
highly significant results and 4 showed significant
results while 10 crosses showing negative heterosis
were non-significant. Twelve crosses showed increase
in height as compared to parents. Out of these 12
hybrids 10 showed positive but non-significant results.
One cross showed highly significant results and one
cross showed significant results. The highest negative
heterosis as compared to the parents was showed by
the cross combinations i.e. Weebli-1 × Maya/Pavon
(-10.88%) followed by the crosses Uqab-2000 ×
Weebli-1 (-7.64%) and Punjab-85 × Weebli-1 (-7.18%).
The highest positive heterosis was shown by the cross
Punjab-85 × Shalimar-88 (4.50%).
1.3 Heterobeltiosis for plant height under normal
and heat stress conditions
Heterobeltiosis studies under normal environment for
plant height indicated that 12 crosses showed increase
over better parental value. Eight out of 12 crosses
showed positive and highly significant heterobeltiosis
and 4 crosses showed non-significant results. However,
30 crosses showed negative heterobeltiosis Table 2.
Among them 12 were highly significant, 6 were