Increasing scarcity of irrigational water is a major threat to sustainable production of cotton (Gossypium hirsutum L.). It could be resolved by developing drought-tolerant cultivars. Osmotic adjustment and cellular membrane stability are well-documented traits that help to sustain yield under drought in cereals. However, their utility in cotton is not well established. Here, we studied genotypic variability and relationships among osmotic adjustment, cell membrane stability and productivity traits under field-induced water stress at the flowering stage. We evaluated a set of cotton germplasm comprising 32 cotton genotypes under contrasting water regimes for measurements of productivity including seedcotton yield, number of bolls per plant and boll weight, and physiological attributes such as osmotic adjustment and cell membrane stability in two field trials. The mean reduction in seedcotton yield due to water deficit was 20 and 43% in 2003 and 2004, respectively. Genotypes differed considerably for relative yield losses due to water stress ranging from 20 to 74%. Significant association between number of bolls and seedcotton yield under a water-limited regime suggests boll retention as the principal determinant of yield in a water-deficit-stress environment. Cell membrane stability varied significantly among the cotton genotypes; however, its association with productivity measurements was not significant in the water-limited regime. The significant positive correlation found between cell membrane stability and osmotic adjustment implicates the role of osmolytes in the protection of various cellular functions, including those associated with cellular membranes. Moderate but significant differences for osmotic adjustment were found among the genotypes in both years. Osmotic adjustment was positively associated with seedcotton yield under the water-limited regime and inversely correlated with the drought susceptibility index. These results demonstrated the contribution of osmotic adjustment in sustaining yield under water-deficit stress in cotton. Thus, like cereals, osmotic adjustment may be useful as a selection criterion in breeding programs with the objective of improving drought tolerance and yield in cotton under water-limited environments; however, the role of cell membrane stability as a drought-tolerant trait requires further investigation.

The idea of enhanced methanol production from cell wall by pectin methyl esterase enzymes (PME) combined with expression of cry genes from Bacillus thuringiensis as a strategy to improve pests control in cotton is presented. We constructed a cassette containing two cry genes (cry1Fa and Cry32Aa) and two pme genes, one from Arabidopsis thaliana (AtPME), and other from Aspergillus niger (AnPME) in pCAMBIA1301 plant expression vector using CAMV-35S promoter. This construction was transformed in Eagle-2 cotton variety using shoot apex-cut Agrobacterium-mediated transformation. The expression of cry genes and pme genes was confirmed by qPCR. Methanol production was measured in control and in the cry and pme transformed plants showing methanol production only in transformed plants, then the non-transgenic cotton plants. Finally, insect bioassays performed with transgenic plants expressing cry and pme genes, showed 100 % mortality for Helicoverpa armigera (cotton bollworm) larvae, 70% mortality for pectinophore gossypiella (pink bollworm) larvae and 95% mortality of Earias fabia, (spotted bollworm) larvae, that was higher than the transgenic plants expressing only cry genes that showed 84%, 49% and 79% mortality, respectively. These results demonstrate that Bt. cry-genes coupled with pme genes is an effective strategy to improve the control of different insect pests.