الفهرس 
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Abstract
The present investigation was conducted in the Department of Agronomy Faculty of Agriculture, Kafr El-Sheikh University. The field experiments were conducted at the Agricultural Research Farm, Sakha Agricultural Research Station, A.R.C., Egypt, during the 2011 and 2012 growing seasons to evaluate all genotypes (14 parents and 40 F1 crosses) under two planting dates.
The main objectives of this investigation were to study and determine the following aspects:
1. Identify the most superior lines and testers for improving yielding ability and fiber properties of cotton.
2. Estimates the general and specific combining ability and their interactions with planting dates as two different environmental conditions as well genetic components.
3. Estimate amount of heterosis for growth habits, yield and its components and fiber properties Studied traits are:
A) Growth traits:
1- First fruiting node (F.F.N.)
2- Number of fruiting branches per plant (N.F.B/P.)
3- Plant height (P.H.)
4- flowering date(flower.)
B) Yield and yield component traits:
1- Seed cotton yield (S.C.Y.)
2- - Lint yield (L.Y.)
3- Lint percentage (L %)
4- Number of bolls per plant (N.B/P.)
5- Boll weight (B.W.)
6- Seed index (S.I.)
C) Fiber properties:
1- Fiber fineness (micronaire value)
2- Fiber strength (Presley index)
3- Fiber length (F.L.)
4- Uniformity ratio (U.R)
The results could be summarized as follows:
Genetic variances
The genetic materials used in the present study involved 14parents and 40 crosses (G. barbadense L.), the parents were classified into two groups. The first group was the lines; Giza 92 (L1) , Giza 84 (L2) , Giza 93 (L3) ,Giza 70 (L4) , PHP(L5) , G84 ( G70 x G51B) Pima 62 (L7) , Pima 62(L6) , G 89 x Pima S6(L8) ,Suven (L9) ,Pima S6 (L10) and the second group was the testers; Giza 45(T1),Giza 86(T2), Kar(T3) and 10229AUST(T4).The two groups were crossed together by using line x tester mating design. The crosses were initiated in the 2012growing season, at Sakha Agric., Res. Station. In 2012 growing season, two experiments were designed in a randomized complete block with three replications to evaluate all genotypes (14 parents and 40 F1 crosses). The results could be summarized as follows:
Genetic variances:
1. The genotypes, parents and crosses mean squares were highly significant for all studied traits in the two sowing dates.
2. The first order interactions for the genotypes, parents and crosses by environment were highly significant for most traits. While, the first order interaction, lines by environment and the second order interaction, line x tester x environment were insignificant for most traits.
The mean performance of genotypes:
1. Both 10229 UST and Giza 45,G89 x Pima S6and kar exhibited the highest means of growth habit traits among lines in the two dates and combined data
2. The highest crosses of growth traits were G 84 x10229 Aust, Pima S6 xG45 , G. 84 x G. 86, G 93 x10229 Aust and{(Giza.84 x
Giza.70 x Giza. 51B)pima62} X G45 .
3. The parents (G. 89 x pima s6), PHP,Suvin,G45 and Karshneseky gave the highest values of yield and yield component traits.
4. The best parents of fiber properties were, {(Giza.84 x Giza.70 x Giza. 51B) X Pima 62} and G. 45, x G. 92 and G. 93.
5. The highest crosses of yield and yield component traits were {(Giza.84 x Giza.70 x Giza. 51B)pima62} X G45, G 84 xKar, G 93 xKar, Suven xKar and PHPxKar.
6. The four crosses; G. 93 x G. 70 x G 93 xKar, {(Giza.84 x Giza.70 x Giza. 51B) X Pima 62}G 45and G70 x10229UST showed the highest means of fiber traits .
Combining ability:
1. The parents G. 89X Pima S6, G84 ,10229UST and pima s6 showed significant general combining ability (G.C.A) effects for most growth habit traits.
2. The parents Karshneseki, 10229UST x and Suvin showed highly significant positive general combining ability effects for yield and yield component traits.
3. G93 and G70 showed highly significant positive values of G.C.A. effects for most fiber properties. These results indicated that the additive genetic variance was important for the inheritance of these traits.
4. The crosses G 86XG 92,Karx pima s6,PHP x10229UST ,G70 x G45,G93 X Kar,G92 X G 45 and G 70 x G 86 showed highly significant positive values of S.C.A. effects for most fiber properties.
Heterosis:
1. The most desirable and useful heterosis relative to both mid and better parent of growth habits were detected by the crosses {(Giza.84 x Giza.70 x Giza. 51B) X Pima 62} x G 45, G 45 x Giza.92 , G 93 x kar, suvin x G 45 and suvin x Kar.
2. The crosses G 93 x kar, 10229 x G. 92 , Suvin x Kar, 10229 x Pima s6 and Kar x Pima s6 exhibited significant and highly significant positive heterosis (desirable) relative to mid and better parents for most yield and yield components traits.
3. The crosses G. 45Xphp,G KarxG93,Pima s6x G 86, G 93x G 86 and G 70x10229 UST showed desirable heterosis of most fiber properties.
Proportion contributions of lines, tester and line x tester:
Proportional contributions showed that lines x testers had higher contribution than testers and lines for most growth traits, yield and yield components traits and most fiber properties.
Gene action:
The results revealed that the magnitude of non-additive genetic variance (2D) was larger than additive genetic variance (2A) for all studied traits at the two dates and combined data.
Heritability estimates:
1. Heritability estimates in broad sense showed high values for all studied more than narrow sense Heritability.