Antioxidant responses to waterlogging stress and subsequent recovery in two Kentucky bluegrass (Poa pratensis L.) cultivars

The antioxidant enzyme activities and gene expressions in leaves of Kentucky bluegrass (Poa pratensis L.) were investigated in response to waterlogging stress and subsequent drainage. Two cultivars contrasting in waterlogging tolerance, ‘Moonlight’ (waterlogging-tolerant) and ‘Kenblue’ (waterlogging-sensitive), were subjected to waterlogging for 28 days (d) followed by 7 d of drainage recovery. Waterlogging stress increased malondialdehyde (MDA), superoxide anion (O2·−) and hydrogen peroxide (H2O2) in both cultivars. Moonlight exhibited greater turfgrass quality (TQ) rating and chlorophyll (Chl) content than Kenblue during the waterlogging and drainage period. After 7 d of drainage, all physiological parameters returned to the control level for Moonlight, but not for Kenblue. Higher activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) as well as more abundance of isozymes were found in Moonlight relative to Kenblue under waterlogging stress. Moonlight showed higher SOD and APX activity and isozymes intensity when compared with Kenblue during the drainage period. The transcript levels of chloroplastic Cu/ZnSOD (Chl Cu/ZnSOD), MnSOD, FeSOD, POD and cytosolic APX (Cyt APX) were higher in Moonlight relative to Kenblue under waterlogging conditions, and higher transcript activities of Chl Cu/ZnSOD, FeSOD and Cyt APX were observed in Moonlight than in Kenblue at 7 d of drainage. The results of this study indicate that higher SOD and APX activity, isozymes intensity and gene expression level in Moonlight relative to Kenblue may play crucial roles in Kentucky bluegrass tolerance to waterlogging stress.