Short-term cold stress in two cultivars of Digitaria eriantha: effects on stress-related hormones and antioxidant defense system

The two cultivars of Digitaria eriantha: cv. Sudafricana (a cold-sensitive cultivar) and cv. Mejorada INTA (a cold-resistant cultivar) were exposed to low temperature and compared in terms of the involvement of abscisic acid (ABA) and catabolites, jasmonates, and antioxidant defense in cold tolerance. Cold stress caused a greater ABA increase in cv. Mejorada INTA than in cv. Sudafricana. In both cultivars abscisic acid glucose ester and dihydrophaseic acid were the most abundant catabolites. Cold treatment decreased JA in leaves of both cultivars. In cv. Sudafricana, 12-hydroxyjasmonate (12-OH-JA) decreased and 12-oxo-phytodienoic acid increased. In regard to antioxidant defense, both cultivars increased the non-protein thiols in response to cold stress. However, reduced glutathione (GSH) level was higher in leaves of cv. Mejorada INTA than cv. Sudafricana. Cold-treated leaves of cv. Sudafricana increased thiobarbituric acid-reactive substances (TBARS), but cv. Mejorada INTA leaves showed no such increase. Superoxide dismutase activity decreased and ascorbate peroxidase activity increased in cold-treated leaves of cv. Sudafricana. No significant change of these enzymes was observed for cv. Mejorada INTA. The cold tolerance of cv. Mejorada INTA could be related to JA, 12-OH-JA and GSH high basal contents, ABA increase, and TBARS stability after cold treatment.