Characterization of water-stress tolerant cotton cultivars based on plant growth and in activity of antioxidant enzymes

The aim of this study was to characterize cotton cultivars based on growth data and on antioxidant enzymes activity, in order to identify better-adapted cultivars to water-stress conditions. Nine genotypes were submitted to 7 days of water suppression starting at 45 days after seedling emergence (phase R1). The essay was carried out in greenhouse conditions, where plants were grown in 5 L vases filled with sandy soil previously fertilized as recommended for the crop. A completely randomized experimental design adopted in a 9×2 (genotypes × water treatment) factorial scheme and 4 replications.  Cultivar classifications were performed by multivariate analysis, using canonical variable and UPGMA cluster analysis. The following growth traits were recorded: Plant height, leaf stalk diameter, number of leaves and root length and weight. Antioxidative activities (SOD, CAT and APX) were also tested by spectrophotometry. Water stress affected all genotypes with different response level.  The genotypes adapted to semiarid environment showed better capacity to grow under water limitation, and also better performance of antioxidative enzymes in order to avoid cellular damages. BRS 286, CNPA 7MH and CNPA 5M were better adapted to drought period and regarded as the best cultivars to use in cotton breeding aiming tolerance to water stress.   Key words: Gossypium hirsutum L., antioxidative enzymes, water stress.