One of the important problems in cotton breeding is the creation of high-yielding, fast-maturing varieties with high fiber yield and quality and their wide use in production. Due to the increase in the number of people on earth and the reduction of irrigated arable land, it is important to get a high quality harvest suitable for different soil and climate regions without expanding the arable land. This research intended to study the variability of the observed characters in the phenotype of the cotton plant during the selection of four F2-F4 hybrid combinations in the conditions of Tashkent, Fergana and Kashkadarya regions. During the research experiments, classical genetic-selection methods of cotton, hybridological analysis methods, comparative morphology, phenological observations and genetic-statistical analysis methods were used. The results showed that the average indicators of this sign were approximately the same in Fergana and Kashkadarya regions, accounted for 116.5 and 117 days, which was 12 days shorter than the growth period of this hybrid in Tashkent region. Similarly, insignificant changes of the above combinations were also observed in the experiments of 2019 and 2020. It was found that in F2 [(F8 L-247 x S-484) x F15 L-248], the fiber length variation was not significantly affected by the environment, the variation ranged from 0.04 inches to 0.07 inches.

The hybrids of medium-fiber cotton were assessed in terms of fiber quality in the Tashkent, Fergana and Kashkadarya regions of the Republic of Uzbekistan. 4 hybrid combinations of different genetic origin were tested. The analysis of the influence of the genotype and the environment on the manifestation of the qualitative parameters of the fiber (length, specific breaking load, micronaire) was carried out. High values were found in hybrids involving the wild species G. trilobum Skovsted and the ruderal form G. Harknessii Brand. as well as varieties Bukhara-6. As a result of three years of experiments, it was found that the genotype and unaccounted factors influence the variability of the fiber length to a greater extent. The genotype rather than the environment significantly affects the specific breaking load of the fiber. The variability of the micronaire fiber is more dependent on environmental conditions.