PEROXIDASE ACTIVITY AS AN INDICATOR OF WATER DEFICIT TOLERANCE IN SOYBEAN CULTIVARS

This study had as purpose to test the hypothesis that peroxidase enzyme activity could be used as an indicator of tolerance to water deficit in soybean cultivars. The experiment was carried out in pots containing 20-L of a Rhodic Hapludox soil in greenhouse conditions. Treatments were arranged in a randomized block design in a 2 x 4 factorial: two water regimes (with and without water deficit) and four soybean cultivars (CD 204, CD 215, CD 225RR and CD 226RR), with four replications. Soybean plants were grown until the beginning of flowering (R1-R2) with soil moisture content near at the field capacity, and then, it started the differentiation of treatments under water deficit by the suspension of water supply. Changes in relative water content (RWC) in leaves, protoplasmic tolerance, peroxidase activity, and plant growth were measured after four days of drought stress and 4-d recovery. The soybean cultivars used in this study have different responses under water deficit conditions. The CD 215 cultivar was the most sensitive to water deficit in the beginning of flowering stage. Soybean cultivars presented variable responses to the peroxidase enzyme activity, and this variable can be used in the selection of soybean genotypes with greater tolerance to drought.