Oxidative damage and antioxidant defenses as potential indicators of salt-tolerant Cenchrus ciliaris L. genotypes

Oxidative stress was used as a tool for a differential characterization of salt-tolerant Cenchrus ciliaris L. genotypes, as part of a genetic improvement program. Four genotypes of Cenchrus ciliaris L. were subjected to gradual salinity stress. After 17 days of 300 mM NaCl treatment, the level of damage in morphological traits was lower in two genotypes, Americana and Biloela (named the salt-tolerant genotypes), than in Texas and Sexual (named the less salt-tolerant genotypes). Oxidative stress characters were evaluated at early time points of salt treatment. Thus, at 48 h, salt tolerance in Americana was correlated with a lower increase in total superoxide dismutase (SOD) activity but a higher increase in total catalase (CAT) activity than in the less tolerant Texas. Salt tolerance was accompanied by a decrease in oxidative damage, evaluated as foliar malondialdehyde (MDA) and O2− content in roots, in salt-tolerant Americana, as compared with the less salt tolerant, Texas. Moreover, in the more salt-tolerant Americana, the decrease in O2− in roots was associated with an enhanced total SOD activity. To validate oxidative damage characters they were measured in Biloela and Sexual, the other two genotypes with contrasting salt tolerance. We propose oxidative stress characters, particularly foliar MDA and root O2− content, as potential indicators of salt tolerance, since they allow a simple, rapid, and cost-effective identification of salt-tolerant Cenchrus ciliaris L. genotypes.