Abstract
Two field experiments were carried out during the 2014 and 2015 seasons to evaluate certain genotypes of Egyptian cotton under well irrigated and water stress conditions. The cross combination Giza 69 x Australy recorded the best values for better parent heterosis for all physiological measurements and earliness index under well irrigated and deficit conditions. Of the female parents, Giza 86 was found to be a good general combiner for most yield characters under both normal and stress conditions, followed by Giza 94. Data illustrated that Giza 45 was the best general combiner for most fiber quality traits under both conditions. The cross combinations Giza 86 x Dandra and Giza 69 x Pima S6 showed significant positive SCA values for seed cotton and lint yield/plant under well irrigated and water deficit conditions. However, the combinations Giza 77 x PimaS6 and Giza 94 x 10229 recorded significant positive SCA effects for seed cotton yield/plant under stress. Whilst, the cross Giza 68 x 10229 recorded significant desirable SCA effects for most fiber quality properties. In this context, the estimates significant positive general and specific combining ability effects indicated that the epistasis and/or dominance effects for F1 hybrid in cotton could be important to a certain extent.
Highlights
MATERIALS AND METHODSIt is a known fact that the phenomena of heterosis is of common occurrence in both cross and selfpollinated crops
The results suggested that high yield does not necessarily depend on high heterotic expression of all yield characters, and high heterosis for some or few component traits, which are associated with yield, can generate significant heterosis in yield
In the present investigation estimates of significant positive general and specific combining ability effects for most characters under study, indicated that the epistasis and/or dominance effects for F1 hybrid in cotton could be important to a certain extent
Summary
It is a known fact that the phenomena of heterosis is of common occurrence in both cross and selfpollinated crops. Cotton which is highly selfpollinated crop show heterosis when hybridization takes place among homozygous varieties. Heterosis is a complex genetical phenomenon, which depends on the balance of different combinations of gene effect as well as distribution of plus and minus allels in the parent of a mating. The ultimate choice of parents in a breeding program is generally based on performance of parents and their F1 hybrids. General and specific combining abilities are more informative than performance, since it reveals the type of gene effects which help plant breeders to devise breeding and selection strategies. The concept of combining ability plays an important role in the identification and selection of desirable parents for exploiting and development of superior hybrids Khan et al (2009)
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