Identification and Selection for Salt Tolerance in Alfalfa (Medicago sativa L.) Ecotypes via Physiological Traits

Salt stress is a serious environmental problem throughout the world which may be partially relieved by breeding cultivars that can tolerate salt stress. Plant breeding may provide a relatively cost effective short-term solution to the salinity problem by producing cultivars able to remain productive at low to moderate levels of salinity. Five alfalfa cultivars, ‘Seyah-Roud’, ‘Ahar-Hourand’, ‘Oskou’, ‘Malekan’ and ‘Sefida-Khan’ were assessed for salt tolerance at mature plant stage. A greenhouse screening system was used to evaluate individual alfalfa plants grown in perlit medium, and irrigated with water containing different amounts of NaCl. Three salt levels were achieved by adding 0, 100 and 200 mM NaCl to Hoagland nutrient solution, respectively. Forage yield, sodium and potassium contents and K/Na ratio was determined. Also, leaf samples were analyzed for proline and chlorophyll contents. The ecotypes Seyha-Roud and ‘Sefida-Khan’ had comparatively less sodium contents than ‘Oskou’, ‘Ahar-Hourand’ and ‘Malekan’ ecotypes, also potassium content increased under saline condition. Forage yield of different alfalfa ecotypes was significantly influenced by the salinity. The ecotypes ‘Malekan’, Ahar- Hourand and ‘Oskou’ were successful in maintaining forage yield under salinity stress. Sodium contents increased due to salinity in all alfalfa ecotypes however ecotypes ‘Ahar-Hourand’ and ‘Malekan’ maintained the highest leaf Na concentration. They showed higher content of K than other ecotypes but had lower K/Na ratio. It was concluded that, two ecotypes ‘Malekan’ and ‘Ahar-Hourand’ were better.