PHENOTYPIC EVALUATION OF COTTON GENOTYPES FOR DROUGHT TOLERANCE AT SEEDLING STAGE

Abstract

Drought stress is a major constraint to sustainable cotton production, making the identification of genotype with desirable growth and root characteristics under limited water availability an important breeding objective. The present study evaluated 60 cotton genotypes under two water regimes i.e. normal and drought conditions using morphological, biomass, leaf, and root-related traits. The experiment was conducted for 40 days at the Cotton Research Station, Vehari, Punjab, Pakistan, using a completely randomized design with two replications. Analysis of variance revealed significant differences among genotypes for all evaluated traits, while genotype × treatment interaction was significant for all traits, indicating considerable variation in genotype response to water availability. Drought stress reduced plant height and number of leaves, whereas root length, root weight, root–shoot ratio, total biomass and several other traits showed comparatively stable or improved performance. Correlation analysis demonstrated strong positive associations of root weight with root–shoot ratio (r = 0.90, P<0.001) and total biomass with stem weight (r = 0.76, P<0.001) under drought conditions, highlighting the importance of biomass partitioning and root development in drought response. Principal component biplot analysis explained 36% of the total variation through the first two components and separated the genotypes into four major clusters. Based on favorable multivariate positioning, NH-161, Malmal, A-555 and BH-180 were identified as promising genotypes, particularly in association with root weight, root–shoot ratio and other desirable growth characteristics under the drought stress conditions. Overall, the results demonstrated substantial genetic diversity among the tested cotton genotypes and indicated that combined assessment of morphological, biomass and root traits through correlation and biplot analysis can assist in identifying promising material for drought-tolerance breeding.