An Integrated Analysis of Genetic Diversity and Physiological Responses to Salinity Stress in 128 Genotypes of Foxtail Millet (Setaria italica L.)

Foxtail millet (Setaria italica L.), a vital crop in semi-arid regions, exhibits strong tolerance to environmental stresses. To investigate genetic diversity and trait relationships, an experiment was conducted with 128 foxtail millet genotypes from Iranian indigenous, foreign, and hybrid cultivars. Stepwise regression analysis showed that Panicle weight (Pw), RDW, Panicle thickness (PT), and Chlorophyll (SPAD value) together explained 73% of the variation in total dry weight (TDW). The trait Panicle weight (Pw) had the highest direct effect on TDW (0.569), consistent with its strong positive correlation (0.785**). Genetic variation was highest for Flag leaf width (110.91), followed by panicle number (71.14). The highest heritability was observed for Flag leaf width (97.51%) and Peduncle thickness (76.88%), indicating these traits are less affected by environmental factors. Building on these findings, a subset of 25 genotypes selected for further evaluation under salinity stress. These genotypes were subjected to a hydroponic experiment with two conditions: a control (0 mM NaCl) and moderate salinity (60 mM NaCl). The study focused on assessing key physiological and biochemical responses, including Proline content and the activity of antioxidant enzymes Superoxide Dismutase (SOD) and Catalase (CAT). The results showed that genotype and condition had a highly significant effect on all three traits, with a significant interaction effect confirming that the genotypic response to salinity stress is not uniform.