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Cotton is an important agro-industrial crop across the globe. Improving the fiber quality and yield potential of cotton are major commercial targets for cotton breeders. The cotton lint yield is computed by multiplying three fundamental yield constituents: average boll weight, boll number per unit ground area, and lint percentage. The cotton species Gossypium arboreum exhibits a wide range of desirable traits, which are absent in the congener Gossypium hirsutum. Four parental lines of G. hirsutum and G. arboreum, with significant differences in boll-related traits, were used to develop the following four F2 populations: Mei Zhongmian × Chimu Heizi (MC), Mei Zhongmian × L-02292-3 (ML), Dixie king × Suyuan 04-44 (DS), and Dixie king × Pamuk (DP), in order to study complex traits, such as boll weight (BW) (g), lint percentage (LP) (%), boll upper width (BUW), boll medium width (BMW), boll lower width (BLU), and boll length (BL) (mm). In segregation populations, extensive phenotypic differences and transgressive segregation were observed. The results show that most of the correlation clusters were negatively associated with boll weight and lint percentage. The positive correlation clusters were observed among boll upper width (BUW), boll medium width (BMW), boll lower width (BLW), and boll length (BL). Seven of the twenty-four extracted principal components had eigenvalues > 1. This accounted for 62.2% of the difference between the four F2 populations. Principal component 1 accounted for 15.1% of the overall variability. The variation in principal component 1 was mainly attributed to boll lower width (BLW), boll medium width (BMW), boll upper width (BUW), boll length (BL), and boll weight (BW) of the ML population. The heritability estimates varied between high, medium, and low for various traits among the studied F2 populations. Interestingly, all traits demonstrated low genetic advance, which indicates that non-additive genes controlled these characters and that direct selection for these traits is not beneficial. The outcome of the present investigation will help to develop cotton cultivars with improved boll weight and lint percentage. [ABSTRACT FROM AUTHOR]

The development of high-yielding heat-tolerant cotton cultivars harboring plastic phenotypes across warming climatic regions is prime objectives of today's cotton breeding programs. We evaluated eight parents and 15 F1 hybrids under normal and heat stress conditions. Agronomic and biochemical characters were analyzed using standard least square, correlation, principal component analysis (PCA), and hierarchical clustering. The results explained a significant reduction in all traits except hydrogen peroxide contents, catalase, and peroxidase activities with a prominent increase under heat stress. A significant positive correlation was observed among all agronomic and biochemical traits. POD was found to have a maximum positive correlation with CAT (0.947) and minimum with boll weight (0.050). PCA showed first two components accounting for 78.64% of the total variation, with 55.83% and 22.80% of the total variation, respectively. Based on multivariate analyses methods 23 genotypes have been placed in 3 groups: tolerant (cluster-3), moderately tolerant (cluster-2), and susceptible (cluster-1). In a general perspective hybrids have better performance across normal and heat stress supports the idea of hybrid adaptability across stress environments. In specific FH-458 × FH-313 cross performed best across both conditions for yield and physiological traits. Hence, the generated information from the present study would support breeders in developing heat-resilient cultivars to endure the prevailing extreme environmental conditions. [ABSTRACT FROM AUTHOR]