الفهرس 
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Abstract
The objective of the present investigation was to evaluate ten Egyptian cotton genotypes under different locations i.e. El-Fayoum, Beni- Souef, Assiut, Sohag and Luxor locations in 2014 and 2015 seasons to determine the interaction between the genetically constitution and locations conditions effects on yield, yield components and fiber properties. Also estimating phenotypic and genotypic stability according to Eberhart and Russell (1966) and Tai (1971) for seed cotton yield (SCY) and lint cotton yield (LCY) of cotton genotypes. The experimental design was randomized complete block design with four replications for each of the five locations in two seasons. The standard analysis of variance of genotypes performance were made for each trait under study, while stability parameter was estimate for seed cotton yield (SCY) and lint cotton yield (LCY). The results obtained could be summarized as follows. 1- Relative magnitude of genotype –environments interaction The results of the combine analysis of variance showed that the effect of year (Y) was highly significant for boll weight (BW), seed cotton yield (SCY), lint cotton yield (LCY), Pressly index (PI), Upper half mean length (UHM) and length uniformity ratio (LUR), while lint percentage (L%) was significant differences for year (Y) effects. locations effect (L) and the locations by years (Y×L) interaction effects were highly significant or significant for all studied traits except for Upper half mean length (UHM) which recorded insignificant mean squares of (Y×L) interaction. However, the effects of genotypes (G) mean squares were highly significant for all yield components and fiber properties. The interaction of years × genotypes (Y×G) mean squares were significant and highly significant for all studied traits except for lint cotton yield (LCY). Mean squares of genotypes × environment interaction (G×L) was highly significant for all studied traits except for micronaire reading (Mic) and Upper half mean length (UHM) which recorded significant (G×L) interaction while lint percentage (L%) was insignificant (G×L) interaction, indicated that the second order interaction years × locations × genotype (Y×L×G) mean squares were significant for lint cotton yield (LCY) and lint percentage (L %) and highly significant for all other traits except for micronaire reading (Mic). This would indicate that the effect of genotypes could be changed by the change of location to location and seasonal changing with respect to these traits 2- Effect of growing season. Results revealed that the values of yield components and fiber properties traits were affected by growing season, years mean square effects were significant for all traits studied. Boll weight (BW), lint percentage (L%), seed index (SI) and lint index (LI) traits gave the highest values in 2014 season, while the traits of seed cotton yield (SCY), lint cotton yield (LCY), yarn strength (Y.St) and Upper half mean length (UHM) were the highest in 2015 season. The variation between traits from season to another may be due to the differences in climatical conditions from season to another. 3-Interaction effects of the different location over two seasons. Mean squares interaction effects of (L×Y) were highly significant for all studied characters except Upper half mean length (UHM mm) which recorded significant differences. The highest and lowest values of boll weight (BW g) were obtained from cotton genotypes which grown at Beni-Souef and Sohag (3.06 g). and Luxor (2.80 g) locations, respectively. Seed cotton yield (SCY K/f) had the highest value (12.43 K/f) and recorded significant differences were obtained of cotton genotypes which grown at El-Fayoum location compared with the other locations. While the cotton genotypes at Luxor location gave the lowest production of seed cotton yield (4.84 K/f).Concerning lint cotton yield (LCY K/f), the highest value of lint cotton yield (LCY K/f) was (15.63 K/f) of the cotton genotypes grown at El- Fayoum location, but the lowest value of lint cotton yield (LCY K/f) was (5.96 K/f) of the cotton genotypes grown at Luxor location. With respect to lint percentage (L %), the cotton genotypes grown at Assuit location gives the highest value of lint percentage (L %), it was (40.02%), while cotton genotypes grown at Sohag recorded lowest value of lint percentage (L %), it was (38.94%).Seed index (SI g) results of cotton genotypes, revealed that the average values ranged from (9.06 g) to (9.86 g) of Luxor and Beni-Souef locations, respectively. Lint index (LI g) trait, that highest value was noticed at Beni-Souef location (6.56 g), but the lowest value was found at Luxor location (5.80 g). All cotton genotypes which grown at EL-Fayoum, location recorded the highest value of micronaire reading (4.32). On the other hand, the lowest value of micronaire reading (Mic) of cotton genotypes was (3.65) at Luxor location. With respect to Pressly index (PI) of all cotton genotypes grown under different locations ranged from (9.27 to 9.64) units at Luxor and Beni-Souef locations, respectively. Yarn strength (Y.St g/tex) trait of all cotton genotypes under different locations was ranged from (1960 to 2055) at Assuit, Sohag and Luxor locations, respectively. Upper half mean length (UHM mm) results indicated that the differences between locations of all cotton genotypes for this trait were ranged from (30.40 mm) at EL- Fayoum and Assuit locations to (30.75 mm) at Beni-Souef and Luxor locations. Length uniformity ratio (LUR %), revealed that the cotton genotypes which grown under different locations recorded values ranged from (83.31 to 83.84) at Beni-Souef and Luxor locations, respectively.