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.

In the irrigated lands of Tashkent province, regionalized wheat varieties are usually planted at a rate of 250 kg/ha, but it would be possible to increase yields and grain quality if a scientifically based optimal sowing rate was recommended for each variety. Another opportunity to increase wheat yields in the region is the development of seed production. Numerous studies and practices have shown that it is possible to increase wheat yields by 20-25 by sowing wheat seeds. In this regard, the most pressing issue is to increase the level of seed germination. In this article, it is important to study the scientifically based sowing norms, physiological maturation of seeds, and their impact on yield and grain quality in order to take full advantage of the potential of regionalized varieties of wheat in irrigated lands. The determination of the most optimal planting norms, taking into account their biological properties, is based on research.