الفهرس 
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Abstract
These study were carried out to evaluate and estimate the stability parameters of line genotypes, four of them belong to the extra long staple category i.e. Giza 87, Giza 88, Giza 88, Giza 92 and (Giza 77 x Pima S6) and five belong to the long staple category i.e. Giza 85, Giza 86, Giza 89, (Giza 89 x Giza 86) and (Giza 89 x Pima S6) at seven different locations in the lower Egypt i.e. Kafr El-Dawar (El-Beheira), Sedi Salim (Kafr El-Sheikh), Belkas (El-Dakahlia), Kafr saad (Damietta), Samanod (El-Gharbia), Menuf (El-Menufia) and Abou Kepeer (El-Sharkia), during the two growing seasons 2007 and 2008. The experimental design was a randomized complete block design with four replications.
The traits study were i.e. seed cotton yield, lint cotton yield, Boll weight, lint percentage, seed index, lint index, earliness percentage, position of the first fruiting node, 2.5% span length, length uniformity ratio, micronaire reading, fiber maturity, fiber elongation, fiber strength and yarn strength.
All traits showed significant mean squares for genotype, environments and genotype x environment interaction. The varieties Giza 88 and Giza 92 surpassed all genotypes from the extra long staple category in most traits at El-Beheira, Kafr El-Sheikh, El-Dakahlia and Damietta location. Also, Giza 86 and the new hybrid (Giza 89 x Giza 86) surpassed all genotype from the long staple category in most traits (yield and some yield components) at El-Gharbia, El-Menufia and El-Sharkia locations.
The combined analysis showed that both the linear and non-linear (poold deviation) components were significant, for all traits. Indicating the presence of both predictable and un-predictable components of genotype-environment interaction. Average stability degrees were recorded for seed cotton yield K.F for Giza 85, Giza 86, Giza 77 x pima S6, Giza 88 and Giza 92; lint cotton yield for (Giza 89 x Giza 86), (Giza 89 x Pima S6), Giza 88 and Giza 92; boll weight for Giza 86, Giza 88 and Giza 92; for lint percentage Giza 86 and Giza 89; seed index for Giza 85, Giza 86, Giza 89, (Giza 89 x Giza 86), (Giza 77 x S6) and Giza 92; lint index for Giza 85, Giza 86 and (Giza 89 x Giza 86); earliness percentage for Giza 85, Giza 89, (Giza 89 x Giza 86), (Giza 77 x Pima S6), Giza 88 and Giza 92; position of the first fruiting node for (Giza 77 x Pima S6) and (Giza 89 x Giza 86); length uniformity ratio for Giza 92; micronalre reading for (Giza 77 x Pima S6) fiber maturity for Giza 86 and Giza 92, while all genotypes under study were unstable for fiber strength and Yarn strength. Both of the varieties Giza 86 and Giza 92 recorded stability degrees in most characters than the rest genotype so, may be considered as breeding stocks for specific traits.