الفهرس 
General and specific combining abilitiesOnly 14 pages are availabe for public view
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Abstract
Twenty one wheat hybrids and their parental genotypes were
evaluated in the Research Farm and Laboratories of the Department of
Genetics, Faculty of Agriculture, Ain Shams University, Shoubra El-
Khema, Cairo, Egypt, in 2016/17 growing season. The genetic analysis
was conducted using Griffing (1956), Method 2, model 1.
Significant differences among genotypes, parents and crosses for all
the studied traits (days to 50% heading, days to maturity, flag leaf area,
plant height, number of spikes/ plant, spike length, number of spikelets/
spike, number of kernels/ spike, 1000-kernel weight and grain yield/
plant). This indicates that, variability exists among these populations may
increase the chance appearance of good new combinations that can be
isolated in the succeeding generations. Parents versus crosses mean
squares as an indication for average heterosis over all crosses were
significant for all the studied traits.
Mean squares of general (GCA) and specific (SCA) combining
abilities were significant for all the studied traits, except spike length for
SCA was insignificant. GCA/SCA ratios were more than unity for all the
studied traits, indicating that the additive type of gene action is of great
importance in the inheritance of these traits. Heterosis over better parents
showed that, the best hybrids were Gemmiza 9 x Giza 168, Sakha 93 x
Giza 168, Sakha 94 x Jawahir-14, Sakha 94 x Bob white, Giza 168 x
Acsad 925 and Jawahir-14 x Bob white for grain yield/ plant and some of
the other studied traits. The best general combiner parents were Sakha 94,
Jawahir-14 and Bob white for grain yield/ plant and some of the other
studied traits. The best SCA hybrids were Gemmiza 9 x Sakha 93,
Gemmiza 9 x Giza 168, Sakha 93 x Jawahir-14, Sakha 94 x Jawahir-14,
Sakha 94 x Acsad 925, Sakha 94 x Bob white, Giza 168 x Jawahir-14,
Giza 168 x Acsad 925, Jawahir-14 x Bob white and Acsad 925 x Bob
white for grain yield/ plant and some of the other studied traits.
The seven parents and their 21 crosses were subjected to heat stress
experiment. Its noticed that the varieties Sakha 94, Sakha 93 and Jawahir-
14 expressed the same banding pattern in control and heat stress, while
the varieties Acsad 925, Bob white , Giza 168 and Gemmiza 9 showed
less banding pattern in heat stress rather than the control. Therefore, the
varieties Sakha 94, Sakha 93 and Jawahir-14 can be ranked as a tolerant
varieties and the others as sensitive ones.
It is concluded to note from these results that most of the tolerant
hybrids which showed no differences in the heat shock protein banding
patterns had at least one of the tolerant parents present in their genotypes.
Key words: Wheat, Combining ability, Heterosis, Heat stress, Protein
electrophoresis, SDS-PAGE, Heat shock, Thermal tolerance.