he promising cotton line CB 58 x Giza 90 was grown compared with Giza 90 and Giza 95 cultivars and a new promising line at four locations during 2016 and 2017 seasons (eight environments) in South Egypt. The randomized complete block design with four replications was used at each location. The characters studied were seed cotton yield, lint yield, boll weight, lint percentage, seed index, lint index, fiber length, length uniformity ratio, micronaire reading and fiber strength. Significant

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... ences were detected among genotypes for all traits except boll weight. In addition, significant differences were found among environments for all characters. Genotype by environment interaction was significant for all studied characters except boll weight, seed index and lint index. The promising line CB 58 x Giza 90 surpassed the commercial cultivars for yield traits but, it did not differ significantly with the promising line [((G.83 x G.80) x G.89) × Australian] for lint percentage. The promising cotton line CB 58 x Giza 90 was equal to the commercial cultivars for length uniformity ratio. The commercial cultivars recorded the highest values for seed and lint index. Giza 95 cultivar recorded the best values for fiber characters. The promising line CB 58 x Giza 90 produced the highest values for most characters at sohag location where it surpassed the commercial cultivars for yield characters and with no significant difference for fiber length. Therefore, it seems necessary to continue evaluating the new cotton genotypes at several locations over an adequate number of years before recommending a given variety for a certain location. Giza 90 cultivar was considered stable across a wide range of environments. Giza 95 cultivar was less sensitive to environmental changes. So it could be more adapted to poor-yielding environments. The genotypes, Giza 90 and the two lines had more general adaptability to all environments.