| Summary: | 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 <i>Gossypium arboreum</i> exhibits a wide range of desirable traits, which are absent in the congener <i>Gossypium hirsutum</i>. Four parental lines of <i>G. hirsutum</i> and <i>G. arboreum</i>, with significant differences in boll-related traits, were used to develop the following four F<sub>2</sub> 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 F<sub>2</sub> 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 F<sub>2</sub> 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.
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