Background: Unravelling the relationship between trichome density and resistance to jassids in upland cotton, nine parental lines, viz. MCU 5, CO 14, CO 17, TCH 1828, KC 2, KC 3, GISV 323, GTHV 15–34, and RHC 1409 were obtained from the Tamilnadu Agricultural University. These genotypes were subjected to molecular analysis using 27 primers, merely the JESPR 154 primer amplifying a 150-bp fragment in genotypes exhibiting the pubescence. Result: This finding validated the association between pubescence and jassid resistance. Further analysis revealed that resistant genotypes (KC 3, GTHV 15–34, GISV 323, and RHC 1409) exhibited significantly higher trichome densities and length compared with susceptible genotypes. These results stalwartly support the hypothesis that trichomes play a pivotal role in conferring resistance to jassids in upland cotton. Conclusion: By breeding cotton varieties with increased trichome density and length, it is possible to reduce jassid infestations, thereby decreasing the reliance on chemical pesticides and promoting a more sustainable agricultural environment.

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.

The parents MCU 5, CO 14, CO 17, TCH 1828, KC 2, KC 3, GISV 323, GTHV 15–34 and RHC 1409 of upland cotton were used for the present study. They were obtained from the Tamilnadu Agricultural University, Department of cotton, Coimbatore. Among the 27 primers used only JESPR 154 primer showed amplified fragment at 150 bp which validates the corresponding parents with hairiness trait conferring resistance to Jassid. The hairy nature of trichome density was observed among the resistant genotypes (KC 3, GTHV 15–34, GISV 323 and RHC 1409). Hairiness confers resistance to jassids was evidence from the results and discussion which would confer breeders develop varieties with high resistance genotypes thereby reducing the jassid infestation. The trichomes were found to confer resistance to sucking pests. This henceforth reduce the pesticide consumption in cotton plants thereby paving the way for a safety environment for ecological species without harming them. Pesticide usage would be lowered with the use of tolerant genotypes. It also paves way for the improvement of future integrated pest management (IPM) programme.