Genetic Dissection of Flowering and Plant Architectural Traits to Develop Early Maturing Compact Upland Cotton Genotypes for High-Density Planting

Earliness in cotton is a highly valued trait that allows the crop to dodge late-season stress and facilitates efficient harvesting, ultimately benefiting farmers with optimal yield. Understanding the genetics of these complex traits is a prelude to designing extra-early maturing cotton genotypes. Two crosses with six generations (ESS-20 x FLT-25 and S-32 x FLT-25: P1, P2, F1, F2, BC1P1, and BC1P2) and one cross with five generations (NNDC-30 x NNDC-47: P1, P2, F1, F2, and F2:3) were field-evaluated for ten earliness and plant architecture traits in cotton. ANOVA presented significant generational differences for most traits. The inadequacy of the Additive-Dominance (A-D) model in explaining trait inheritance using scaling and joint-scaling tests highlighted the presence of epistatic gene actions. Further, the analysis of gene action unveiled the predominance of dominance effect [h] and dominance x dominance [l] epistatic effect, influencing the expression of most traits. Contrasting signs of [h] and [l] effects for these traits suggested the occurrence of duplicate epistasis across crosses. Therefore, population improvement strategies and heterosis breeding could be effective in designing extra-early maturing genotypes. All traits exhibited quantitative inheritance, with partial and overdominance favouring early maturity. Notably, days to flowering and boll opening, exhibited negative heterosis, suggesting the efficient development of short-duration cotton hybrids. Besides, the study also predicted less than one gene block for the majority of traits, suggesting a significant role of complex non-allelic interaction in trait expression. These findings offer valuable insights for strategizing efficient breeding methods to develop early-maturing cotton genotypes.