Assessment of Alfalfa varieties under salt stress through morpho-physiological and biochemical traits using a...

Salt stress is widely recognized as a major abiotic constraint that limits plant growth and productivity. Alfalfa (Medicago sativa L.), a globally important forage legume, exhibits considerable variability in salt toll,erance across its diverse cultivars. The present study aims to provide a comprehensive evaluation of eight alfalfa varieties by examining their morphological, physiological, and biochemical responses at four NaCl levels (0, 60, 120, and 180 mM NaCl).

Salt tolerance is quantified using a combination of the membership function method, correlation analysis, principal component analysis, and different indices of salt tolerance.

High salt stress significantly reduced plant height (PH), shoot dry weight (SDW), root dry weight (RDW), and number of leaves (NOL) of all alfalfa varieties by 47.21%, 61.36%, 64.19%, and 59.91%, respectively, compared with the control. Similarly, physiological traits including relative water content (RWC) and stomatal conductance (SC) declined by 43.93% and 60.87%, respectively, whereas electrolyte leakage (EL) and malondialdehyde (MDA) increased by 267.35% and 178.48%, respectively. Salt stress also markedly altered antioxidant responses among varieties, with superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities increasing by 111.27%, 170.87%, and 125.87%, while V5 (A'erjienong) and V2 (Weinasi) consistently showed tolerance, whereas V4 (Fudina) and V8 (Qianjing) exhibited susceptibility across varying stress levels. Principal component analysis (PCA) classified the traits into three main groups, which explained 93.15% of the total variation, and identified SOD, POD, CAT, SS, and Car as crucial factors affecting salt tolerance.

Comprehensive membership function analysis indicated that variety V5 (A'erjienong) was the most tolerant, while variety V4 (Fudina) remained the most sensitive. This study highlights the importance of morpho-physiological and biochemical traits, along with stress tolerance indices, as reliable indicators for evaluating salt tolerance in alfalfa. Future integration of these traits with advanced genetic and breeding approaches may facilitate the development of high-yielding, salt-tolerant alfalfa cultivars.