Effects of salt stress on the germination of two contrasting Medicago sativa varieties.

Selection strategies for increased salt tolerance in Medicago sativa must involve several growth stages, with the germination stage as a particularly important stage. At this stage, M. sativa is known to be more sensitive to salt than later growth stages. Cultivars differ significantly in their capacity to germinate under saline conditions. For this consideration and in order to analyze the response to salinity, initial screening at the germination stage for two varieties of M. sativa was undertaken. Seeds were germinated in Petri dishes under control treatment (0 mM NaCl) and four concentrations of NaCl (100, 150, 200 and 250 mM). Results from ANOVA showed that variation in root length (RL), fresh root weight (RFW) and shoot fresh weight (SFW) was explained by variety effect. The variation in hypocotyl length, (HL) SFW and RL was explained by the interaction of variety x treatment. Under salt stress, there was a major reduction (46, 66%) in final germination rate (GR) when seeds were geminated in 250 mM NaCl. The RL and HL were affected by salt stress and their respective values were reduced by more than 40% in 200 mM NaCl. The Californian variety was lesser affected by salt stress for RL and RFW while the local variety from El Hemma showed the lowest reduction for SFW. Further work is needed to asses these effects in later growth stages and in field conditions under salt stress.