الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 167 |  |  |
| | | from | 167 | | |
Abstract
Eight genotypes namely, Giza 80, Giza 83, Dandera, Giza 89, Giza 85, Giza90, Giza 91 and the promising genotype Giza 83 x (Giza 75 x 5844) were grown during the two successive seasons 2003 and 2004 at five different locations, i.e.; Beni-Suef, El-Fayoum, El-Minia (Middle Egypt), Assuit and Sohaag (Upper Egypt). A complete randomized blocks design trail with four replications was conducted in each of the ten environments (combination of five locations in two years). The analysis of variance and stability of performance were calculated for each of the studied characters. The results obtained could be summarized as follows :-
1. Mean squares for twelve characters for eight genotypes grown at five locations for the two years, (2003 and 2002) :-
1. Egyptian cotton genotypes differed in their genetic potential for earliness, yield and yield components, and fiber properties traits whereas, mean squares of genotypes were highly significant for all characters under study. The genotypes Dandera and Giza 90 revealed the highest values for earliness index. The promising genotype Giza 83 x (Giza 75 x 5844) surpassed all studied genotypes in boll weight, seed cotton yield and lint yield. The promising genotype Giza 83 x (Giza 75 x 5844) and Giza 80 gave the highest values for lint percentage, while Dandera variety and the promising genotype Giza 83 x (Giza 75 x 5844) had the highest values for seed index and lint index. The genotypes Giza 80, Giza 89 and Giza 91were the highest for fiber properties except Giza 80 (for 50 % span length and length uniformity ratio) and Giza 89 (for length uniformity ratio).
2. Highly significant mean squares for environment were recorded for all characters except Pressley index. However, locations effect was significant or highly significant for all characters under study, except length uniformity ratio. Year’s effect was significant to highly significant for all yield components and fiber properties traits, except for boll weight.
3. The first order interaction genotype x year was significant or highly significant for boll weight, seed index, lint index and all fiber properties traits.
4. The genotype x location interaction was significant or highly significant for all yield and its components characters, and for micronaire reading and 50 % span length.
5. The second order interaction genotype x year x location was insignificant for all traits except boll weight, seed cotton yield, lint yield and lint index.
6. The mean squares of genotype x environment interaction were significant or highly significant for all characters under study. Theses results indicated that the productivity of any genotype is the outcome of the interaction between the genetical constitution and environmental conditions. For this reason, cotton should be grown under suitable environmental conditions to achieve the highest yield and the best quality.
2. The mean performance :-
2.1. Effect of years :-
2.1.1. Earliness percentage :-
The second year (2004) was earlier in maturity than the first year, whereas the effect of years was insignificant for earliness index.
2.1.2. Yield and yield components :-
Results revealed that the climatic conditions during the first year (2003) affected favorably all characters under study in comparison with the second year of 2004. The differences among the two years were significant for all characters, except boll weight.
2.1.3. Fiber properties :-
Results revealed that the climatic conditions during the first year (2003) were more favorable than those in the second year (2004) and affecting all fiber properties. The differences were significant among the two years in all characters.
2.2. Effect of the locations :-
2.2.1. Earliness percentage :-
El-Fayoum and Assuit governorates were the earliest locations.
2-2-2- Yield and yield components :-
The ten locations differed significantly concerning seed cotton yield and yield components characters. Assuit governorate favourably affected number of bolls / m2, seed cotton yield, lint yield, and seed index as compared with the other locations. While, Beni-Suef was better location for boll weight, lint percentage and lint index On the other hand, El-Minia and Sohaag governorates were lower than other locations tested in all characters studied.
2.2.3. Location effect on the fiber properties :-
The ten locations had significant effect on the studied fiber properties, Assuit governorate had the highest values of micronaire reading. Whereas, Sohag governorate favourably affected fiber strength, fiber length (2.5 % and 50 % span length) and recorded the highest values as compared with the other locations, while the lowest values of fiber properties were observed in El-Fayoum and El-Minia locations.
2.3. Effect of the interaction between years and locations:-
It could be concluded that the different traits changed in their means from location to another and from year to another, but generally it can be seen that Assuit in 2003 was the best environment for number of bolls / m2, seed cotton yield and seed index, El-Minia in 2003 for boll weight, and Beni-Suef was the best environment for lint yield in 2003 and lint index at 2004. Otherwise, Sohaag at 2003 year gave the best fiber properties.
2.4. Effect of genotypes :-
2.4.1. Earliness percentage :-
Mean of earliness percentage revealed that Giza 90 was the earlier genotype, while Giza 80 was the latest one.
2.4.2. Yield and yield components :-
1. Mean number of bolls / m2 showed that Giza 90 and Giza 83 had the highest values.
2. Giza 90 and the promising genotype Giza 83 x (Giza 75 x 5844) surpassed all studied genotypes in boll weight, seed cotton yield and lint yield, while Giza 89 gave the lowest yield values.
3. Regarding lint percentage and lint index, the promising genotype Giza 83 x (Giza 75 x 5844) and Giza 80 gave the highest values for these traits, while Dandera variety and the promising genotype Giza 83 x (Giza 75 x 5844) had the highest value for seed index
2.4.3. fiber properties :-
1. Giza 85 and Giza 80 reached the highest values for micronaire reading and fiber length.
2. As for fiber strength and fiber length, it was clear that Giza 80 and Giza 89 had the highest values.
3. The highest values for length uniformity ratio were Giza 91 and the promising genotype Giza 83 x (Giza 75 x 5844).
2.5. Effect of the interaction between years and genotypes:-
Significant interaction effects were detected for boll weight, lint yield, seed index, lint index and all fiber properties traits under this study.
These results give evidence that the genotypes differed in their responses to the environmental conditions from one year to another.
This means that the superiority of a certain genotype depends on the conditions prevailing during the growing season.
2.6. Effect of the interaction between locations and genotypes:-
1. Evidently, Giza 90 grown in Sohaag and Assuit produced the highest values of earliness percentage.
2. All genotypes gave the highest number of bolls / m2 and seed index in Assuit governorate except Giza 89 (for number of bolls / m2) and Giza 91 (for seed index), which gave the highest number of bolls / m2 at Beni-suef.
3. Beni-suef gave the high values of boll weight and lint index for all genotypes except for Giza 90 (for boll weight) and Giza 83 (for lint index) that recorded high values at Assuit.
4. From the results of seed and lint cotton yields, it is apparent that for producing the highest seed and lint cotton yields, it is recommendable to grow Giza 80, Giza 83, Dandera, Giza 85 and Giza 90 genotypes at Assuit, the promising genotype Giza 80 x (Giza 75 x 5844), Giza 91 and Giza 89 at Beni-Suef, to get the highest yield.
5. Regarding to lint percentage, Giza 80 and the promising genotype Giza 83 x (Giza 75 x 5844) gave the highest lint percentage compared to the other genotypes in Beni-Suef and El-Minia, and Giza 83 in El-Fayoum.
6. With respect to fiber properties, it is evident that to obtain the best fiber quality, it is recommendable to grow Giza 80, Giza 91 and the promising genotypes Giza 83 x (Giza 75 x 5844) in Beni-Suef, Giza 83, Dandera, Giza 85, Giza 90 in Assuit and Sohaag while Giza 89 must grow in El-Fayoum and El-Minia.
2.7. Effect of the interaction between years, locations and genotypes :-
This second order interaction affected insignificantly all traits of yield and its components and all fiber property traits except, boll weight, seed cotton yield, lint yield and lint index which were significantly affected.
The significantly affected traits indicate the important role of each of (genotypes, locations, years, locations x years interaction, as well as genotypes x environment interaction) that affect boll weight, seed cotton yield, lint yield and lint index traits..
Therefore, it seems necessary to continue evaluating cotton genotypes, old or newly produced, by growing them at several locations over an adequate number of years before recommending any variety for a certain location.
3. Genotypic stability for different genotypes :-
The relative ranking of genotypes according to their mean performance over ten environment was not the same for all characters showed that the relatively unpredictable component of variance (the deviation from linear response, λ ) of the genotype-environment interaction might be more important than the relatively predictable component (the coefficient of linear response, α ).
Estimations of genotypic stability revealed varying degree of stability for the different genotypes. This study shows that the most stable genotype over ten sample environment was Dandera variety which exhibited the highest number of stable characters, followed in a descending order by Giza 83, the promising genotypes Giza 83 x (Giza 75 x 5844), Giza 89 (in the same order), Giza 90, Giza 91 (in the same order), Giza 80 and Giza 85.
Many investigators reported that the stability with which the plant breeders are concerned dose not imply general constancy of phenotype in varying environment, but it implies stability in agriculturally important characters particularly yield (Allard and Bradshaw, 1964; Eberhart and Russel, 1966; and Tai, 1971). Therefore, the following genotypes may be considered as breeding stocks for specific traits.
Seed cotton yield and lint yield Giza 83
Boll weight Giza 89
Lint percentage Dandera
Lint index promising genotype Giza 83 x (Giza 75 x 5844)
Pressley index Giza 80, Giza 83 and Giza 89
2.5 % span length Giza 90
50 % span length promising genotype Giza 83 x (Giza 75 x 5844)
Length uniformity ratio Giza 80, Giza 83, Giza 91 and promising genotype Giza 83 x (Giza 75 x 5844)
4. Estimation of the genetic coefficient of variability heritability in broad sense and genetic gains :-
1. High heritability estimates (over 50 %) were obtained for earliness percentage; all yield and yield components and all fiber properties traits.
2. High expected genetic advance (over 7 %) was computed for earliness index, number of bolls / m2, seed index lint index and micronaire reading. Moderate genetic gains (from 5 % to 7 %) were estimated for boll weight, lint percentage and 50 % span length. On the other hand, low genetic gains (below 5 %) were estimated for yield characters, Pressley index, 2.5 % span length and length uniformity ratio.
3. The genetic coefficient of variability was intermediate (from 5 % to 7 %), for earliness index, and lint index, while it was low for the other characters.