Antioxidant system response of different wheat cultivars under drought: field and in vitro studies

The participation of the antioxidant system in the drought tolerance of whe at cultivars (Triticum aestivum L.) was studied under field and in vitro co nditions. Under field conditions, drought tolerance was evaluated by the ca pacity to maintain the grain yield under drought, which was higher in cvv. Elite and La Paz than in the sensitive cvv. Oasis and Cruz Alta. Tolerant c ultivars showed lower relative water content (RWC) and lower above-ground v egetative biomass than sensitive cultivars. Field assays did not show a cle ar correlation between water-stress tolerance and antioxidant system behavi our. However, when leaves of cvv. with contrasting drought tolerance were s ubjected to osmotic stress in vitro, clear differences in the antioxidant s ystem activity and oxidative damage between cvv. were observed. In the tole rant cultivar Elite, it was possible to observe an increase in ascorbate pe roxidase (APX), superoxide dismutase (SOD) and glutathione reductase (GR) a ctivities, a higher glutathione (GSH) and ascorbate content and less oxidat ive damage than in the sensitive cultivar Oasis, which showed no changes or only slight decreases in the enzyme activities. These results indicate tha t water stress tolerance is in part associated with the antioxidant system activity, and suggest that the behaviour of the antioxidant system in vitro assays can be used as an early selection tool.