Combining ability analysis and breeding for early- maturing cotton (Gossypium hirsutum L.) varieties using Line x Tester analysis

The development of early-maturing and high-yielding cotton varieties is a strategic priority in regions with limited growing seasons and increasing climate variability. This study investigates the genetic basis of earliness and evaluates the combining ability of selected cotton lines and cultivars using the Line x Tester hybridisation method. A set of lines (L-158, L-75, L-1703, L-1858, L-257) and testers (L-302, L-597, and the standard cultivar S-6530) were crossed to produce F1 hybrids and their F2 and F3 populations. Field trials were conducted under arid continental conditions in Uzbekistan using standard agronomic practices. The results revealed significant variation in the length of the vegetative period among parental lines and hybrids. General and specific combining ability (gca and sca) analyses showed that lines L-158 and L-1858 had the highest negative gca effects for the vegetative period, indicating their potential for breeding early-maturing genotypes. F1 hybrids displayed predominance and overdominance effects toward early-maturing original lines, while F2 and F3 generations exhibited wider-than-parental variation, leading to the identification of ultra-early recombinant lines. Several new breeding lines, including L-215, L-218, and L-178, demonstrated superior performance in earliness and agronomic traits. These findings provide a valuable framework for optimising selection strategies in cotton breeding programs and highlight the relevance of hybridisation for developing climate-resilient, early-maturing cultivars.