Change in several Antioxidant Enzymes Activity and Seed Yield by Water Deficit Stress in Soybean (Glycine max L.) Cultivars

Drought stress is one of several environmental factors greatly limiting crop production. In order to study the effect of water deficit on antioxidant enzymes activity and seed yield of five soybean cultivars, an experiment was conducted in two growing seasons in 2008 and 2009. The experimental design was randomized complete block in a split plot arrangement with four replications. Irrigation treatments were (S1, 50; S2, 100 and S3, 150 mm evaporation from the Class "A pan" evaporation) and cultivars were ('L17', 'Clean', 'T.M.S.', 'Williams*Chippewa' and 'M9'). The results showed that, water deficit stress increased antioxidants content [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX)] significantly, but content of them were more at mild than high water deficit stress (S2>S3>S1). Furthermore, water deficit stress, decreased total chlorophyll content, number of pods per plant, thousand seed weight, seed yield and harvest index in all of cultivars. Among cultivars, 'L17' and 'Williams*Chippewa' produced the highest seed yield at the optimum condition of irrigation and both water deficit stress levels, respectively. Assessment of correlation results indicated that, there was a positive and significant correlation among SOD and seed yield in both water deficit stress levels, too.