Oxidative stress indicators as selection tools for salt tolerance in Chloris gayana

Oxidative stress indicators, malondialdehyde (MDA) accumulation and chlorop hyll retention, were tested as tools for salt-tolerance screening in Chlori s gayana (Kunth), a forage grass exhibiting inter- and intracultivar variab ility in the response to salt stress. Three types of experimental system we re compared: salt shock, gradual salt treatment and leaf segments floated o n control and saline solutions. Results followed the same trend in the thre e systems, but leaf segments or gradually salinized plants are the most con venient. Lower mean MDA and higher mean chlorophyll content were found unde r salinity in cv. 'Katambora', which is considered, from previous field tri als, to be more salt tolerant than cv. 'Boma'. Nevertheless, chlorophyll co ntent did not give consistent results in other tests and it is not recommen ded for selection purposes. Within cv. 'Boma', clones rating higher in a sa lt tolerance evaluation under greenhouse conditions had lower MDA content u nder salinity and lower mean MDA ratios between salt-treated and control sa mples. The survival of 80 'Boma' plants under increasing NaCl concentration was assessed and MDA was measured in the leaves of every plant before the final NaCl level was reached, to assess whether it was predictive of surviv al capability. MDA values were significantly lower in the group surviving l onger, thus, a selection based on low MDA values would have enriched the or iginal population with more tolerant individuals.