This research was conducted to study effects of G × E interaction on 38 selected genotypes of cotton with two commercial cultivars Golestan and Sepid (control) in a randomized complete block design with three replications at three locations in Golestan Province in 2014-15. The measured characteristics were included: plant height, sympodial length, sympodial number, boll number, boll weight, seed cotton yield and earliness. Analysis of variance showed that genotype effect is significant in 1 or 5% probability levels on measured traits except for boll number and earliness. A significant interaction effect between genotype × locations in yield showed different variation trends in various locations. So that genotype 29 had the best performance in Hashemabad station but genotypes 24 and 18 showed their best performances in Gonbad and Anbarolum station respectively. Stability parameters were calculated and genotype No. 8 was defined according to regression slope close to 1 as the most stable genotypes among. This genotype had a smaller share in genotype and environment interaction according to Rick ecovalans and Shukla stability variance parameters and 10 and 33 were the most unstable genotypes in terms of performance. GGE biplot method showed that the first two principal components regression model explained 74% of the observed changes. GGE biplot graph plotted by software reflected the superior genotypes TJ82, ER26, DB29, DB19, DB25 and ER36 respectively. Also Hashemabad has been identified as appropriate region for ER26 genotype and TJ82 was identified as the best and most stable genotype.

In order to evaluate salt tolerance in seedling stage, seeds of 11 hybrid and new varieties of cotton, compared to commercial cultivars of Golestan as control were planted in pot. Factorial experiment in a completely randomized design with three replications was conducted at the Cotton Research Institute of Iran in 2014. The first factor was salinity levels and the second factor was 12 genotypes. The characteristics were included: germination percentage, seedling height, seedling fresh and dry weight, dry weight of shoot and also water in root and stem tissue was observed among genotypes. The results showed that the genotypes studied traits measured showed significant differences at 1% or 5%. Different level of salt water reduce plant high and length of shoot and root. Irrigation of pots by salt water decreased root and stem weight, while among genotypes studied SB8 was superior the percentage of germination, shoot length, root fresh weight and dry weight of seedlings in view of other genotypes and 8S26, S29 were superior in view of shoot fresh weight and water content than control. Correlation coefficient was positive and significant between germination and stem and root length. Also, the length of the stem with other traits such as root length, root dry weight were positive and significant. Regression analysis revealed that root and shoot dry weight suitable criterion for selection is salt tolerant cultivars.