Abstract
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.
Highlights
Plants submitted to environmental stresses respond with several physiological and biochemical chain reactions in order to minimize or avoid the cell damages
We evaluated the response to water stress in nine Brazilian cotton cultivars, based on growth analysis and in activity of antioxidative enzymes, during early growth
Nine cotton cultivars were submitted to water suppression at beginning of flowering and evaluated as tolerance based on growth traits and activity of antioxidative enzymes
Summary
Plants submitted to environmental stresses respond with several physiological and biochemical chain reactions in order to minimize or avoid the cell damages. The genotypes from M. galante types have broad adaptation to dry environments, they show less fiber yield than latifolium ones. The effect of water stress is most critical in reproductive phase, mainly in boll and fiber developments (Baldo et al, 2009; Ball et al, 1994). Baldo et al (2009) evaluated cotton genotypes submitted to 45 days of water suppression and observed severe reduction on plant height, stem diameter, number of leaves, number of leaves and reduction of 25% on boll yield, as well. In Brazil, the main commercial cultivars growth in Savanna region have limited yield in environments with water irregularities. Considering the world climatic changes, mainly those related to water availability, the development of cultivars tolerant to drought is a valuable strategy adopted by several plant breeder in several countries. We evaluated the response to water stress in nine Brazilian cotton cultivars, based on growth analysis and in activity of antioxidative enzymes, during early growth
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