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.

Due to its very important agronomic value and nutritional quality, Medicago sativa L. is considered as the queen of fodder and the first cultivated forage crop in the world. In field conditions, M. sativa is exposed to several biotic and/or abiotic constraints that affect its quality. In this regard, research is still underway to improve M. sativa resistance to many biotic stresses and, in this context, we analyzed the responses of a core collection of 10 varieties of M. sativa to Phoma medicaginis infection. Results from ANOVA showed that most growth parameters exhibited significant differences between the studied varieties. Nevertheless, only the number of healthy leaves among infection parameters varied significantly between the varieties. The local variety Gabès2355 exhibited the highest biomass. Positive correlations were found between the measured parameters. PCA based on the traits showing significant differences among the studied lines showed that the Gabès variety formed a separate group. Cluster analysis revealed that the studied varieties are classified into three major groups. The first group is formed by Gabès2353, the second group is composed of the Californian and El Hamma varieties, and the third group is constituted of the seven remaining varieties. Gabès2355 was the most tolerant to the Pm8 strain of P. medicaginis while Magna601 variety was the most susceptible. These two varieties will be useful to analyze the physiological and genetic determinants for M. sativa tolerance to P. medicaginis infection.

Medicago truncatula is an omni-Mediterranean species grown as an annual forage legume. In addition to its small genome size and simple genetics, M. truncatula harbors several attributes, which make it an attractive model forage plant. In this study, we investigated the variation of responses in ten parental lines of M. truncatula to Phoma medicaginis infection. Plants were cultivated in the growth chamber under controlled conditions and were inoculated after two months with P. medicaginis. At harvest, 13 quantitative traits of growth and pathogenicity were measured. Results from ANOVA showed that the variation of analyzed parameters was explained by the effect of line. All measured parameters, except the root fresh weight, showed significant difference among the 10 studied lines. Most tolerant lines are those with the lowest ratios of the number of infected and dead leaves. Studied lines were clustered into three groups according to their responses to P. medicaginis infection. The most resistant TN6.18 line and most sensitive F83005.5 to P. medicaginis are useful for the exploration of physiological mechanisms and genetic determinants for M. truncatula tolerance to this constraint.