Abstract
Pakistan's agriculture, especially the cotton area is facing serious threat of water shortage, which is negatively affecting the sizeable foreign reserves. Besides other irrigation management practices, selection of drought tolerant varieties can support to tackle the issue. The current study was aimed at the assessment of drought tolerance potential of various Bt cultivars of Gossypium hirsutum L. Under the current study, sixteen cotton cultivars were placed for germination in petri dishes under distinct osmotic potentials with seven different concentrations of PEG-6000 (i.e., 0, 5, 10, 15, 20, 25 and 27 percent, having osmotic potential of 0.0,-0.05,-0.148,-0.295,-0.491, 0.735 and-0.846 MPa respectively). The results revealed significant differences among various traits of all genotypes. It was observed that seed germination and root length increased up to concentration level of 25% PEG-6000 (at-0.735 MPa) whereas increment in shoot length stopped further. Root/shoot ratio increased until PEG concentration of 20% and then ceased. NIBGE-8 was the best performer under all simulated osmotic adjustments with maximum mean germination percentage of 62.86 %. The growth parameters of NIBGE-8 recorded on 12th and 18th days after sowing were noted as root length (6.87 and 9.9) cm, shoot length (5.9 and 6.37) cm, root/shoot ratio (1.03 and 1.23), root length-index (597 and 843) and shoot-vigor index (539 and 576) respectively. The results of study revealed that the genotypes NIBGE-8, NIBGE9, BH-201 and RH-668 were found osmotic stress tolerant while Mubarak, CEMB-88 and DEEBEL were found highly sensitive to drought conditions.