To evaluate the effects of drought stress on seed germination and seedling growth traits in different ecotypes of crown vetch (Securigera varia L.), a factorial experiment was conducted using a completely randomized design with three replications. Ten native seed ecotypes were collected from Hamadan, Nahavand, Paveh, Semnan, Sanandaj, Sarvabad, Saghez, Kermanshah, Ilam, and Marivan. Drought stress was imposed using polyethylene glycol (PEG 6000) solutions at osmotic potentials of 0 (control), –2, –4, –6, and –8 bar. After 14 days, traits including germination percentage and rate, mean germination time, radicle and plumule length, seedling dry weight, seed vigor index, and allometric coefficient were measured. Results indicated that increasing drought intensity from 0 to –8 bar significantly reduced germination and seedling growth indices. Germination percentage declined from 100% in some ecotypes to 37.67% in the Marivan ecotype at –8 bar, while the Nahavand ecotype exhibited the highest germination rate (85.33%) at the same stress level. The germination rate decreased from 5.29 under control conditions to 0.73 under severe stress in the Marivan ecotype. The mean daily germination in the Nahavand ecotype decreased from 1.7 (control) to 0.63 (–8 bar), whereas the Sanandaj ecotype demonstrated the greatest reduction from 6.9 to 1.7. Mean germination time increased with stress severity, reaching 6.9 days in the Hamadan ecotype at –8 bar compared to 2.5 days under control conditions. Daily germination speed also decreased, reaching a minimum of 0.15 under severe stress, while the germination rate coefficient in the Semnan ecotype increased to a maximum of 0.20 under mild stress (–2 bar). Radicle and plumule lengths, seedling dry weight, and seed vigor index decreased across all ecotypes, with the allometric coefficient showing significant reductions, particularly in the Sanandaj, Marivan, and Saghez ecotypes. Overall, drought stress negatively affected physiological processes and water uptake efficiency, leading to diminished seed vigor and uniformity. Based on hierarchical cluster analysis, the Nahavand and Semnan ecotypes exhibited high performance across most drought levels and were classified in the resistant group, indicating their potential for use in breeding programs and cultivation under water-limited conditions. |
