Evaluation of Growth and Agronomic Performance of Upland Cotton (Gossypium hirsutum L.) Germplasm from the Kazakhstan Gene Pool

Upland cotton (G. hirsutum L.) is one of the world’s most important commercial fiber crops. The Turkestan region of Kazakhstan is the world’s northernmost cotton-growing region. A four-year field experiment was conducted at the experimental station of the LLP “Agricultural experimental station of cotton and melon growing” from 2021 to 2024. A total of750 lines of G. hirsutum were studied based on phenological, morphological, and agronomic traits. A total of 8 hectares was dedicated to the experiment. The soil comprises light sierozems, which include low humus content, high carbonate content, and relatively low absorption capacity. The study was conducted under average temperatures of 22.9 °C and precipitation totals from 0.9 to 71 mm in 2021–2024. Results revealed significant differences among these years for all studied traits (p < 0.001). According to the average membership function values of 13 traits, the cluster heat map indicated a clear separation into groups, such as low-yielding and late-maturing accessions, and high-yielding and early-maturing accessions. Overall, 41 accessions out of 750 accessions were selected as early-maturing and high-yielding from the 2021–2024 period. This study is the first report on the development of a classification system based on more valuable phenological, morphological, and agronomic traits in the Kazakhstan Cotton Collection. The results demonstrate substantial genetic variability and highlight the potential for developing cotton cultivars adapted to stress-prone environments.