LAUSR

Chromium-VI (Cr (VI)) is a toxic metal pollutant to both plants and animals. In this study, we cultured two transgenic cotton cultivars (J208 (herbicide-resistant), Z905 (insect-resistant)) and their hybrid line (ZD14) in hydroponic media using 0, 10, 50, 100 µM Cr/L for 7 days. Leaf-related growth parameters such as leaf length and width considerably declined. Decrease in leaves’ fresh biomass was less in Z905 followed by ZD14 and J208, while the leaves dry biomass was less in Z905 followed by J208 and ZD14, respectively. Tolerance potential of plant height, root dry weight and leaf dry weight of both transgenic cotton cultivars significantly decreased at Cr concentration (100 µM) as compared with their hybrid line. Cr accumulation in roots tissues was higher (> 90%) than leaf tissues. Stress biomarkers (i.e., (Malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ), total soluble protein (TSP)) as a whole upregulated in leaf tissues of all experimental cultivars. Differential changes in superoxide dismutase (SOD) activity were observed, while peroxidase (POD), catalase (CAT) and glutathione-reductase (GR) activities almost showed increasing trend in all cultivars under exceeding levels of Cr. Correlation studies, in terms of principal component analysis (PCA), revealed that 75.36% of the total variation was present among all the traits. The leaf-based ultrastructural modifications at 100 µM Cr stress level occurred more in Z905 followed by J208 and ZD14. All these changes revealed differential role of experimental cotton cultivars against Cr stress. Hybrid line (ZD14) performed well in comparison with its parental cultivars (J208, Z905) as a whole. Deeper molecular studies like transcriptomic and metabolomic need to be carried out to explore the genetic facts regarding such differential responses among these cotton cultivars under Cr stress.