الفهرس 
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Abstract
The genetic materials used in the present study included six
barbadense varieties and 30 hybrids resulting through complete dialle crosses mating design. These varieties were Giza 45-(PI), Giza-70 (P2), Giza-88 (Pl), Giza-75 (P4). Giza-85 (ps) and Giza-89 (P6). The main objectives of this study were to establish i) the potentiality of heterosis expression for growth attributes, seed cotton yield and its components and fiber traits; ii) the magnitudes of general, specific combining abilities. the different types of gene action and their interaction with the two locations; Le. Sakha and El-Serw and iii) heritability in broad and narrow senses
Studied traits:
A) Vegetative and earliness traits:
L First fruiting node (F.F.N.)
2. Days to first flower (D.F.F.)
3. Days to first opening boll (D.F .O.B)
4. Number of fruiting branches per plant (N.F.B./ P)
5. Plant height (p.H.)
6. Earliness index (E.I.)
B) Yield and yield components traits:
I. Seed cotton yield per plant (S.C. Y JP) 2. Lint cotton yield per plant (L.C. Y JP)
J. Boll weight (B.W.) 4. Number of open bolls per plant (No. B./ P)
5. Lint percentage (L.%) 6. Seed index (S.1.)
C) Fiber traits:
1. Fiber fineness (F.F.) 2. Fiber strength (F.S.)
3. Fiber length al 2.5% S. L. 4. Fiber length at 50%) S.l.
In 1998 growing season the parents and their F 1 hybrids were
evaluated at Sakha and El-Serw Agriculture Research Stations in a randomize complete block design with four replications.
The obtained results can be summarized as follows:
I. Genotypic variation!
Genotypes mean squares showed the presence of highly significant for all studied traits. In the same time. the genotypes by locations interactions were significant for all studied traits except for fiber fineness, indicating that these genotypes showed different performances with different locations.
II. The mean performances of r:enotypcs:
The performances of genotypes showed that Giza-89 (P6) was the earliest variety in the ease of first fruiting node and days to first opening boll. While. Giza-85 (P5) was the earliest for days to first flower. The results also revealed that the (P5 x P6) and (PI x P6) hybrids were the earliest for first fruiting node and days to first opening boll, respectively. In the same time, Fir hybrid (P6 x P5) exhibited the best values for days to first flower and earliness index. In addition; the highest yielding variety was Giza-88 (P3). while Giza-45 (PI) was the lowest parent for yield and yield components. The highest yielding hybrids were obtained for yielding when Giza-45 (PI) and 89 (P6) were involved among their parents. Concerning fiber traits the best variety which exhibited the highest values were Giza-45(P1), Giza 70 (P2) and Giza-88 (P3) for all studied fiber traits. The (PI x P6). (P2 x P3) and (P3 x P1) hybrids were the best hybrids fiber traits.
III. Heterosis:
A. Vegetative and earliness traits:
The results showed that the estimated amounts of heterosis from
the mid-parents versus the F 1.lr hybrids indicated that the significant values ranged from 0.803% to 4.696%) for earliness index and number of fruiting branches per plant, respectively. On the other hand, heterosis over better-parent was not of economical importance.
B. Yield and yield components traits:
The significant amounts of heterosis over the mid-p8Ients versus
Fl,lr hybrids ranged from (4.940% to 33.149%) for seed index and seed cotton yield per plant. respectively. In the same time. heterosis versus the better-parent exhibited significant values (desirable) for seed cotton yield per plant and lint cotton yield per plant.
C. Fiber traits:
Heterosis versus mid and better-parents exhibited undesirable
values for all studied fiber traits.