Comparative assessment of okra and non-okra leaf cotton (Gossypium hirsutum L.) genotypes for drought tolerance

Abstract Cotton production worldwide is adversely affected by drought stress, and the variation in drought tolerance among genotypes can be attributed to differences in their physiological, morphological, and root-related parameters. In upland cotton, there are two major leaf types: okra and non-okra. To investigate genetic variations related to drought tolerance, a study was conducted using two cotton genotypes from each leaf type (IUB 14052, IUB 14053, isolines of IUB-13, and MM-58 for okra leaves; IUB-13 and MM-58 for non-okra leaves) under both normal and drought conditions for two seasons. The experiment followed a factorial layout with a completely randomized design. Cotton genotypes were examined for root, morphological, physiological, and fibre-related variables using genotype × treatment × year interactions. Traits such as transpiration rate, stomatal conductance, chlorophyll contents, leaf area, seed cotton yield, number of nodes, fibre strength and ginning out-turn were higher in okra leaf type genotypes as compared to non-okra leaf type genotypes. As a result, genotypes of okra showed less reduction during drought in all parameters indicated above. Furthermore, under drought conditions, root parameters such as primary root length, lateral root numbers, root fresh weight, and root dry weight increased in okra leaf type accessions, indicating that okra leaf cotton genotypes have a greater drought tolerance capacity. Correlation studies demonstrated a negative correlation between stomatal conductance and leaf area in okra leaf genotypes. This correlation ultimately led to an increase in boll weight and seed cotton yield for okra leaf genotypes. This relationship underscores the role of resource allocation and stomatal conductance in enhancing the overall drought tolerance and productivity of okra leaf cotton genotypes.