Antioxidant responses to water deficit by drought-tolerant and -sensitive sugarcane varieties

Water deficit is the major yield-limiting factor of crop plants. The exposure of plants to this abiotic stress can result in oxidative damage due to the overproduction of reactive oxygen species. The aim of this work was to study the antioxidant-stress response of drought-tolerant (SP83-2847 and SP83-5073) and drought-sensitive (SP90-3414 and SP90-1638) sugarcane varieties to water-deficit stress, which was imposed by withholding irrigation for 3, 10 and 20 days. The drought-sensitive varieties exhibited the lowest leaf relative water content and highest lipid peroxidation, hydrogen peroxide (H2O2) and proline contents during the progression of the drought-stress condition. The antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPOX) and glutathione reductase (GR) activities changed according to variety and stress intensity. SP83-2847 exhibited higher CAT and APX activities than the other varieties in the early stage of drought, while the activities of GPOX and GR were the highest in the other varieties at the end of the drought-stress period. A Cu/Zn SOD isoenzyme was absent at the end of drought period from the SP90-3414-sensitive variety. The results indicate that lipid peroxidation and early accumulation of proline may be good biochemical markers of drought sensitivity in sugarcane.