Evaluation of uncharacterized quinoa (Chenopodium quinoa Willd.) accessions for salinity tolerance during seedling...

Salinity stress is a major constraint to crop establishment and productivity in arid and semi-arid regions, necessitating the identification of salt-tolerant crops and accessions.

This greenhouse study assessed the salinity tolerance of 22 quinoa (Chenopodium quinoa Willd.) accessions, including uncharacterized accessions, seedling emergence, and early seedling growth under six irrigation water salinity levels (ECiw ≈ 1, 3, 6, 9, 12, and 15 dS m^-1). A completely randomized design with three replications was employed. Salinity tolerance was assessed using the salinity tolerance index (STI) and membership function value (MFV), and accessions were classified through hierarchical cluster analysis.

Increasing salinity significantly reduced seedling emergence, delayed emergence, and decreased growth and biomass (P ≤ 0.01). At 15 dS m^-1, emergence declined by 66.7%, and biomass decreased by more than 90%. Salinity altered ion accumulation, increasing Na⁺ and Ca²⁺ concentrations while decreasing K⁺ concentration and the ionic ratios (K⁺/Na⁺ and Ca²⁺/Na⁺). Among the accessions, PI 634923 exhibited the highest salinity tolerance, followed by PI 698783, PI 698773, PI 698780, and PI 698775. Biomass-related traits showed stronger associations with overall tolerance than seedling emergence traits. The threshold salinity corresponding to 50% STI was estimated at approximately 10.5 dS m^-1 for seedling emergence and the early growth stage.

Overall, the study reveals substantial genetic variability in quinoa and identifies promising accessions for saline environments. The inclusion of previously uncharacterized germplasm provides novel insights into breeding programs and supports the development of climate-resilient cropping systems.