Drought stress is considered to be a major factor responsible for reduced agricultural productivity, because it is often linked to other major abiotic stresses, such as salinity and heat stress. Understanding drought-tolerance mechanisms is important for crop improvement. Moreover, under drought conditions, it is possible that growth regulators are able to protect the plants. Brassinosteroids not only play a regulatory role in plant growth, but also organize defense mechanisms against various tresses. This study aimed to evaluate the effect of brassinolide on physio-biochemical amendment in two contrasting cultivars (drought-tolerant RH 725, and drought-sensitive RH 749) of Brassica juncea under drought stress. Two foliar sprayings with brassinolide (10 and 20 mg/L) were carried out in both cultivars (RH 725 and RH 749) at two stages—i.e., flower initiation, and 50% flowering—under stress conditions. The results clearly revealed that the activities of antioxidative enzymes and non-enzymatic antioxidants (carotenoids, ascorbic acid, and proline) increased significantly in RH 725 at 50% flowering, whereas 20 mg/L of brassinolide showed the most promising response. The different oxidative stress indicators (i.e., hydrogen peroxide, malondialdehyde, and electrolyte leakage) decreased to a significant extent at 20 mg/L of brassinolide spray in RH 725 at 50% flowering. This study indicates that brassinolide intensifies the physio-biochemical attributes by improving the antioxidant system and photosynthetic efficiency in RH 725 at 50% flowering. It is assumed that enhanced production of proline, improvement of the antioxidant system, and reduction in the amount of stress indicators impart strength to the plants to combat the stress conditions.

Background: Cotton is a natural fibre grown in over 100 countries worldwide and is a key agricultural crop that provides raw material for various industries (Radhakrishnan, 2017). One effective strategy to address yield and productivity issues, as well as reduce cultivation costs, is to utilize the Gossypium arboreum species. This species has the ability to thrive in rainfed conditions, is resistant to sucking pests and requires fewer inputs compared to Bt cotton hybrids. Methods: Twenty-nine genetic male sterility -based intra-arboreum cotton hybrids were evaluated for yield and fibre quality traits compared to the standard check AAH 1. The study was conducted in a randomized block design with three replications at the research area of the cotton section, Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar during the Kharif season of 2023. Result: Analysis of variance showed significant differences for all traits. The standard heterosis for seed cotton yield varied from -47.1% (AAH 73) to 23.67% (AAH 59). Hybrid AAH 59 displayed the highest positive standard heterosis for lint yield (35.03%) and ginning outturn (9.22%), while the highest standard heterosis for seed index (29.14%) was observed in hybrid AAH 60. Based on standard heterosis, hybrids AAH 59, AAH 54, AAH 66 and AAH 58 showed promise for seed cotton yield and its related traits, while hybrids AAH 61, AAH 47, AAH 56 and AAH 55 performed well for seed cotton yield and fibre quality traits. These heterotic crosses can be utilized for enhancing seed cotton yield and improving fibre quality.