This study examines the base water potential ( b) required for germination in several European populations of Echinochloa crus-galli, a significant agricultural weed, from Spain, Greece, Norway, and the Czech Republic. Seeds were collected in summer/autumn 2023 and sent to the University of Padova (Italy). Initial germination tests revealed varying dormancy levels among populations. To uniformly break seed dormancy, seeds were scarified with 96% sulphuric acid for 8 minutes, thoroughly washed with distilled water, and air-dried for 48 hours. Germination trials were conducted at constant 24 °C to estimate b using polyethylene glycol (PEG) 6000 to simulate eight water potentials (-0.05, -0.10, -0.25, -0.38, -0.50, -0.80, -1.00, -1.25 MPa); additionally, distilled water was used as control. For each population and water potential, four replicates of 50 seeds were tested. Germination was monitored every 2-3 days germinated seeds were recorded and removed. Besides, physical seed traits, including total area, perimeter, and circularity, were analysed by scanning 100 randomly selected seeds per population and processing images in ImageJ software. Statistical analyses in R were used to estimate b with drc and drcSeeds packages, differences between b were examined using Student's t-test. Differences in seed dimensions among populations were assessed via one-way ANOVA and Tukey’s HSD post hoc test (p < 0.05). Results revealed significant variation in b and seed traits. The Norwegian population had the lowest b (-1.81 ± 0.04 MPa), indicating greater drought tolerance, followed by the Greek population (-1.11 ± 0.01 MPa). The Spanish and Czech populations showed the highest b (-0.93 ± 0.01 MPa and -0.92 ± 0.01 MPa, respectively), with no significant difference between them. Seed dimensions also differed significantly, the Spanish population had the smallest seeds (1.61 ± 0.02 mm²) and the most spherical shapes, while the Greek population had the largest seeds (2.79 ± 0.08 mm²), and Norwegian seeds were the most elongated. These findings provide valuable insights into the germination patterns of E. crus-galli and seed traits across different populations. Furthermore, these results are crucial for the development of predictive models for weed emergence, offering practical applications for improving management strategies for this globally problematic species.
