Relationship and dissection of compact plant architecture traits amenable for mechanical harvesting in cotton

The need for mechanical harvesting in cotton production has become paramount as labor costs continue to rise. Efficient machine harvesting requires short and compact cotton plants. This study developed ten F1 populations by crossing five Indian-origin cotton genotypes using a half-diallel mating design. Field trials were conducted in two seasons, Kharif 2022 and summer 2023, at Coimbatore, India. Significant genetic variability was observed across all plant architecture traits, with strong G × E interactions (P ≤ 0.01), highlighting clear opportunities for breeding compact high-yielding cotton types. A consistent negative correlation between plant height and seed cotton yield in both environments suggested that shorter plants provided greater yield stability. An ideal plant height of 75-110 cm was identified as the most suitable for mechanized harvesting. Within this ideal range, architecture traits such as zero monopodia, internode and branch lengths showed a consistent negative association with yield, while plant density, sympodial branch origin and number were positively linked to higher yield. Stepwise regression identified the groups of mainstem internode (1st-4th nodes) and sympodial branch lengths (lower, middle, upper) as key yield-influencing traits, offering targets for breeding compact, high-performing cotton types. Pooled values indicated an ideal mean mainstem internodes lengths (MIL) of approximately 5.2 cm and sympodial branches lengths (SBL) of approximately 19.9 cm, with shorter internodes enhancing plant sturdiness and uniformity, while reduced sympodial length improved canopy openness, light penetration and harvest efficiency with minimal trash intake. The findings provide practical recommendations on compact plant architecture traits, particularly ideal internode and branch lengths, to enhance yield potential and facilitate mechanical harvesting in cotton.