Assessing alfalfa (Medicago sativa L.) tolerance to salinity at seedling stage and screening of the salinity tolerance traits

Salt is among the most harmful agents that negatively influences crop yield. Alfalfa is an important perennial forage crop that exhibits wide cultivar variations in salt tolerance. Developing salt-tolerant alfalfa plants is a promising way to utilize salinized land. A comprehensive method was developed to achieve reliable and effective evaluation of alfalfa salt resistance. This included principal components, membership functions and cluster and stepwise regression analyses. These were used to analyse the salt tolerance coefficients of 14 traits and to evaluate 20 diverse alfalfa cultivars at the seedling stage. The various morphological root parameters of six alfalfa cultivars with contrasting salt tolerance were also tested by a scanning apparatus. According to the comprehensive evaluation value (D value), one highly salt-tolerant, two salt-tolerant, four moderately salt-tolerant and 13 salt-sensitive alfalfa cultivars were screened. A mathematical equation for the evaluation of alfalfa salt tolerance was established: D' = -0.126 + 0.667SFW + 0.377SDW + 1.089K⁺ /Na⁺  + 0.172SFW/RFW (R²  = 0.988; average forecast accuracy of 96.95%), where four indices were closely related to the salt tolerance: shoot fresh weight, ratio of shoot fresh weight to root fresh weight, shoot dry weight and ratio of K⁺ to Na⁺ in the shoot. We also found that SSA correlated strongly with SFW, SDW, K⁺ /Na⁺ , D values, while SRV correlated obviously with SFW, SFW/RFW and D values after 150 mm NaCl treatment. In conclusion, the SFW, K⁺ /Na⁺ , SDW, SFW/RFW, SSA and SRV could be used as indicators of salt tolerance in alfalfa seedlings grown under 150 mm NaCl treatment.

Effect of saline water on seed germination and early seedling growth of the halophyte quinoa

Salinization is increasing on a global scale, decreasing average yields for most major crop plants. Investigations into salt resistance have, unfortunately, mainly been focused on conventional crops, with few studies screening the potential of available halophytes as new crops. This study has been carried out to investigate the mechanisms used by quinoa, a facultative halophytic species, in order to cope with high salt levels at various stages of its development. Quinoa is regarded as one of the crops that might sustain food security in this century, grown primarily for its edible seeds with their high protein content and unique amino acid composition. Although the species has been described as a facultative halophyte, and its tolerance to salt stress has been investigated, its physiological and molecular responses to seawater (SW) and other salts have not been studied. We evaluated the effects of SW and different salts on seed germination, seedling emergence and the antioxidative pathway of quinoa. Seeds were germinated in Petri dishes and seedlings grown in pots with SW solutions (25, 50, 75 and 100 %) and NaCl, CaCl2, KCl and MgCl2 individually, at the concentrations in which they are present in SW. Our results demonstrated that all salts, at lower concentrations, increased the germination rate but not the germination percentages, compared with control (pure water). Conversely, seedlings were differently affected by treatments in respect to salt type and concentration. Growth parameters affected were root and shoot length, root morphology, fresh and dry weight, and water content. An efficient antioxidant mechanism was present in quinoa, activated by salts during germination and early seedling growth, as shown by the activities of antioxidant enzymes. Total antioxidant capacity was always higher under salt stress than in water. Moreover, osmotic and ionic stress factors had different degrees of influence on germination and development.