Abstract
Drought is one of the major abiotic stresses that significantly reduces seed cotton yield worldwide. Therefore, Drought
tolerance is a complex phenomenon that comprises a combination of morphological and physiological parameters which results
in the enhancement of drought tolerance in cotton. Therefore, in the present study 150 cotton genotypes were evaluated for
drought tolerance by planting at two water regimes i.e., normal water and limited water conditions. Data were recorded for
morphological and physiological parameters i.e. root fresh length (FRL), shoot fresh length (FSL), lateral root numbers (LRN),
root fresh weight (FRW), shoot fresh weight (FSW), shoot dry weight (DSW), weight /length ratio(W), root dry weight (DRW),
plant weight (PW), the difference in shoot fresh weight and shoot dry weight (SDWR), stomatal conductance (SC), canopy
temperature (CT), water potential (WP), osmotic potential (OP) and relative water contents (RWC) at the seedling stage.
Principal component analysis (PCA) of seedling at normal water conditions explained PCA1 35.21% and PCA2 15.25% of the
total variance. The cluster analysis of the recorded data for the morpho-physiological parameters grouped 150 genotypes into
six clusters. First Cluster included 16 cotton genotypes, 2nd cluster having 44, clusters 3, 4, 5, and 6 contains 22, 52, 10, and 6
genotypes respectively. In water stress conditions PCA1 containing 18 cotton genotypes, 2nd cluster having of 32 cotton
genotypes, clusters 3, 4, 5, and 6 contain 14, 35, 30, and 21 genotypes, respectively. The use of morpho-physiological seedling
traits associated with drought resistance can facilitate breeding strategies to evolve cotton genotypes having tolerance against
drought stress in the changing climatic conditions. Screening of available cotton genotypes for drought tolerance in controlled
greenhouse conditions can shorten the duration with improvement in efficiency for screening.
Keywords: Cluster analysis, cotton, drought tolerance, morpho-physiological traits, seedling traits, principal component
analysis (PCA).
Muhammad Asif, Asif Ali Khan, Hafiza Masooma Naseer Cheema, Zafar Iqbal. (2022) Genetic variability in diverse cotton germplasm for drought tolerance, Pakistan Journal of Agricultural Sciences, Volume 59, Issue 1.
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