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Triticeae Genomics and Genetics 2014, Vol.5, No.2, 1-11
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5
negative and significant and 3 negative and
non-significant. Among 14 hybrids showing positive
heterosis 8 crosses were highly significant 2 were
significant and 3 were positive and non-significant.
One cross showed no heterobeltiosis. Crosses showing
highest negative values were Weebli-1 × Shalimar-88
(-34.57%), Chenab-2000×Shalimar-88 (-32.07%) and
Punjab-85×Shalimar-88 (-29.48%). Maximum positive
values were exhibited by the crosses Maya/Pavon ×
Uqab-2000 (13.28%) and Inqilab-91 × Maya/Pavon
(13.11%).
1.10 Heterosis for grain yield under normal and
heat stress conditions
Percentage increase of F
1
over their mid parental
values for grain yield per plant under normal
conditions revealed that 21 crosses showed positive
heterosis and 21 crosses showed negative heterosis.
Maximum positive heterosis was manifested by the
cross combinations Uqab-2000 × Punjab-85 (28.70%),
Chenab-2000×Uqab-2000 (27.94%) followed by
Uqab-2000×Chenab-2000 (26.31%). However,
maximum negative heterosis was shown by the cross
combinations Chenab-2000 × Inqilab-91 (-21.14%)
followed by its reciprocal cross Inqilab-91×
Chenab-2000 (-18.99%) and Weebli-1 × Maya/Pavon
(-18.71%).
Percentage increase of F
1
’s over their mid parents for
grain yield per plant under stress environments
showed that only 10 crosses exhibited positive and
statistically significant heterosis over mid parental
values. While, 2 crosses showed positively significant
values and 7 showed positive and non-significant
results. Twenty three crosses showed negative values
as compared to their mid parental values. Out of these
23 hybrids 18 were highly significant, 1 was
significant and 4 were negative and non-significant.
Maximum positive heterosis was recorded by cross
combination Shalimar-88 × Uqab-2000 (27.02%)
followed by Maya/Pavon × Weebli-1 (21.63%) and
Weebli-1 × Punjab-85 (20.88%). Maximum negative
heterosis was exhibited by the cross combinations
Maya/Pavon×Chenab-2000 (-32.58%), Chenab-2000×
Maya/Pavon (-32.01%) followed by the cross
Chenab-2000 × Shalimar-88 (-28.17%).
1.11 Heterobeltiosis for grain yield under normal
and heat stress conditions
Heterobeltiosis for grain yield per plant under normal
conditions indicated that percentage increase of F
1
’s
over better parents showed that 13 crosses out of 42
showed positive increase over better parental value.
However, only 7 crosses were found highly significant,
one cross found significant and 5 crosses showed
non-significant results. 29 crosses showed negative
heterobeltiosis with 21 crosses showed negative and
highly significant heterobeltiosis, 3 crosses showed
significant and 5 cross combinations showed
non-significant results. Maximum positive
heterobeltiosis values were shown by the cross
combinations Uqab-2000 × Punjab-85 (15.58%) and
Chenab-2000 × Uqab-2000 (13.06%). Maximum
negative heterobeltiosis was shown by the cross
combinations Punjab-8 × Weebli-1 (29.41%),
Chenab-2000× Inqilab-91 (-29.29%) and Inqilab-91 ×
Chenab-2000 (-27.36%).
In case of heterobeltiosis 35 cross combinations
showed decline over better parental values under heat
stress conditions. Among them 32 crosses showed
negative and highly significant heterobeltiosis and 3
crosses showed significant results. Only 7 crosses
reported positive heterosis with 4 crosses showing
positive and highly significant, 2 positive and
significant and 1 positive but non-significant.
Maximum negative heterobeltiosis was shown by the
cross combinations Weebli-1×Maya/Pavon (-46.54%),
Weebli-1 × Shalimar-88 (-38.28%) and Maya/Pavon ×
Chenab-2000 (-37.36%). Maximum positive he-
terobeltiosis was indicated by the cross combinations
Shalimar-88 × Uqab-2000 (13.62%) and Inqilab-91 ×
Punjab-85 (11.24%).
2 Discussion
Terminal heat stress in wheat is an area of major
concern in Pakistan and it needs improvement. In
temperate climatic conditions terminal heat shocks are
restrictive factor during anthesis and grain filling
(Reynolds
et al
, 1994). The researchers like Chen
et al
.
(2000)
utilized late sown conditions and plastic sheet
tunnel to induce heat stress at the time of anthesis and
they suggested weight of grains in a spike and yield as
selection criterion against heat stress. Significant
decrease in wheat production resulted due to average
temperature above 15
0
C during grain filling stage
(Weigand and Cuellar, 1981).
In wheat breeding like other crops proper utilization
and choice of parental material is a prerequisite to