An integrated phenotypic and molecular approach to identify salinity-tolerant lentil (Lens culinaris Medik) genotypes

Salinity in soil and irrigation water has emerged as a serious challenge to global agricultural productivity. Lentil (Lens culinaris Medik.) is highly sensitive to salinity, particularly during early seedling establishment, which adversely affects growth and development. Systematic screening at the seedling stage can therefore serve as an effective strategy to identify novel sources of salt-tolerant donors. In this study, 50 elite breeding genotypes from ICARDA breeding program were evaluated for seedling-stage salinity tolerance under salt stress (electrical conductivity of 8 dS m^-1) and control conditions through pot culture. Important morpho-physiological traits, including shoot and root length and their biomass were recorded at 30 days after sowing, revealing substantial genetic variability. Based on the cumulative salt tolerance index (CSTI), 35 genotypes were classified as salt sensitive, eight as moderately tolerant, and seven as salt tolerant, with "X2018-482-S5" as the most tolerant and "FLIP2014-083L-S9" as the most sensitive. Selected tolerant genotypes were further evaluated under saline field conditions, where X2018-482-S5, ILL7547, X2011S-89-23-S1, X2011S-91-77-2-S1, and ILL6819/ILL6207-S2 exhibited stable growth and yield performance comparable to the tolerant checks PSL9 and PDL1. Gene expression analysis revealed coordinated upregulation of the High-Affinity Potassium Transporter (HKT) and NAC domain-containing protein-72 in tolerant genotypes, with significantly higher transcript levels compared to sensitive check FLIP2014-083L-S9 at 6 and 12 h post treatment with 100 mM NaCl treatment, indicating enhanced ion homeostasis and stress-responsive regulation. Overall, the integration of seedling-stage phenotyping, field validation, and molecular analysis provides robust evidence for identifying promising salinity tolerant lentil genotypes for breeding programs targeting salt-affected environments.