The development of high-yielding heat-tolerant cotton cultivars harboring plastic phenotypes across warming climatic regions is prime objectives of today’s cotton breeding programs. We evaluated eight parents and 15 F₁ hybrids under normal and heat stress conditions. Agronomic and biochemical characters were analyzed using standard least square, correlation, principal component analysis (PCA), and hierarchical clustering. The results explained a significant reduction in all traits except hydrogen peroxide contents, catalase, and peroxidase activities with a prominent increase under heat stress. A significant positive correlation was observed among all agronomic and biochemical traits. POD was found to have a maximum positive correlation with CAT (0.947) and minimum with boll weight (0.050). PCA showed first two components accounting for 78.64% of the total variation, with 55.83% and 22.80% of the total variation, respectively. Based on multivariate analyses methods 23 genotypes have been placed in 3 groups: tolerant (cluster-3), moderately tolerant (cluster-2), and susceptible (cluster-1). In a general perspective hybrids have better performance across normal and heat stress supports the idea of hybrid adaptability across stress environments. In specific FH-458 × FH-313 cross performed best across both conditions for yield and physiological traits. Hence, the generated information from the present study would support breeders in developing heat-resilient cultivars to endure the prevailing extreme environmental conditions.

To understand the effect of heat stress on morphology and physiology of the cotton, eight cotton genotypes with their 15F1 hybrids (five lines, three testers) were grown in the field conditions under randomized complete block design (RCBD) with two treatments i.e. normal and high-temperature stresses with two replications followed by split-plot arrangement. Data were collected for biochemical and yield-related parameters. Mean values of all studied traits were reduced significantly under high-temperature stress whilst the mean value of lint%, catalase activity, total soluble proteins, peroxidase, and carotenoids were increased under high-temperature. Under both conditions, the number of bolls, boll weight, seed cotton yield, lint index, seed mass per boll, hydrogen peroxide content, catalase activity, total soluble proteins, carotenoids, and chlorophyll contents had high heritability values along with high genetic advance percent mean which revealed, these traits were controlled by additive gene action. The lint%, seed index, short fiber index, fiber strength, fiber fineness, upper half mean length and peroxidase activity had high heritability with moderate genetic advance under heat stress conditions which showed, these traits were controlled by non-additive gene action. Under both temperature conditions, FH-458, IUB-65, CRS-2, and FH-313 were good general combiners for physicochemical and yield-related traits. The cross combination of IUB-013× CRS-2 and FH-458× FH-313 were good specific combiner for plant height and seed cotton yield whilst for fiber quality and biochemical traits, the best specific combiners were VH-329× FH-313 and IUB-013× CRS-2. These identified parents and cross combinations might be used for improving already present commercial varieties under high-temperature stress.

The production of cotton is negatively affected by salinity. For this purpose, 8 parents and their 16 F1 hybrids were evaluated under saline stress (15 dSm⁻¹) in Line × Tester fashion. Mean values of plant height, number of bolls plant⁻¹, boll weight, lint weight, seed cotton yield plant⁻¹, seed index, no. of seeds boll⁻¹, seed mass boll⁻¹, lint mass boll⁻¹, seed volume per 100 seeds, fiber strength, fiber length, lint%, K⁺, K⁺/Na⁺ ratio, CAT, TSP, chlorophyll a, b, and relative water contents decreased under salt stress whilst the values of lint index, seed density, fiber fineness, Na⁺, H₂O_2, SOD, POD carotenoids, malondialdehyde, phenolic contents, ascorbic acid, and flavonoids increased under saline conditions. Under saline MS-71× CRS-2007, MS-71× KAHKASHAN, and IUB-65 × FH-312 exhibited performed better than other genotypes for most traits. For fiber quality traits IUB-65× CRS-2007 and IUB-65× FH-312 showed the highest value under salt stress. Improved identified cotton genotypes can enhance our capacity to grow cotton in salt-affected soils and the key morpho-biochemical traits can potentially be exploited to obtain higher and more stable crops yield under stressed environments.

Drought is one of the major abiotic stresses limiting cotton productivity, particularly in arid and semi-arid regions. The screening at the seedling stage has been extensively utilized to accelerate the process of selection, but the role of growth, water status, and oxidative traits can change with moisture conditions. Understanding this dependence on moisture-level is essential for trait-based phenotyping and drought-resilient breeding. A greenhouse study was conducted using forty upland cotton accessions grown under 100%, 75%, and 50% field capacity in a two-replications factorial completely randomized design. After two weeks of sowing, stress was imposed, and measurements were recorded at 45 days. Analysis of variance, regime-specific trait summaries, principal component analysis, and K-means clustering were used to interpret the dataset. Drought had decreased the shoot length and relative water content and changed the covariance pattern among traits. ANOVA revealed that genotypes, moisture treatment, and the interaction of genotype and treatment had significant effects on all traits. Multivariate analysis revealed a trait architecture shift as moisture decreased. ELWL and RL were observed to play a major role in principal component structure under normal water conditions, whereas POD and H2O2 had a dominant role under moderate and severe drought. Cluster centroids further distinguish between profiles related to higher antioxidant activity. The findings revealed that cotton seedlings are moisture-level specific instead of being determined by a hierarchical set of traits under drought stress. This study can be useful for selecting drought screening traits in cotton.