Salinity tolerance of lentil is achieved by enhanced proline accumulation, lower level of sodium uptake and modulation of photosynthetic traits

Lentil (Lens culinaris, Medik.), an accessible low-cost high-quality protein form for many people, is a salt-sensitive legume, which already at an electrical conductivity (EC) of 3 dS/m (similar to 30 mM NaCl) has a yield loss of about 90% compared to other crops. Identifying salinity-tolerant lentil germplasm is nowadays of primary importance for ensuring the production of superfood and the sustainability of the lentil industry. In this study, four cultivars Castelluccio di Norcia, Eston, Ustica and Pantelleria were grown up to a complete life cycle, in an open field, in soils conditioned with 100 mM NaCl and were compared with the same cultivars grown in unsalinized soils. Growth parameters, osmolytes and phenotypic characteristics of lentils were assessed. Our results evidenced different mechanisms specific for each tolerant cultivar. Pantelleria was the cultivar that mostly accumulated sodium in shoot and root and used it in addition to proline as osmoregulatory. Ustica accumulated less sodium and calcium than Pantelleria but more chlorine in root and enhanced also the production of the osmoregulatory. Castelluccio accumulated less sodium but more calcium and sulphates than the other two resistant cultivars, producing at the same time also osmolytes. The preference of ion uptake and compartmentalization can depend on the growth environment. PANT and UST are islander, therefore, prevalently in contact with sodium and chlorine, while CAST originated from central Italy is cultivated in soil where calcium and sulphate are the most abundant element.