Studies on the ecology of dyer’s woad: a common non-crop weed worldwide

Abstract Dyer’s woad ( Isatis tinctoria L.) is a noxious and invasive weed that has predominantly spread globally in non-cropped areas. However, recent observations indicate that it has begun to invade cropped areas as well, necessitating effective management strategies to mitigate its impact in both cropped and noncropped environments. The objective of this study was to determine the effect of environmental factors in an incubator (temperature, light/dark period, salinity, osmotic potential, pH levels) and seed burial depths (in a greenhouse) on the germination of I. tinctoria . Results showed that under normal conditions (25 ºC, exposed to light on filter paper in Petri dishes placed in an incubator), the seeds exhibited no dormancy, achieving 96% germination within 5 days. Among the temperature treatments, germination was highest at 25 and 20 ºC (96 and 94%, respectively), while no germination occurred at 5, 10, and 40 ºC. There was no effect of light treatments (12/12 light/dark, 24 h dark, and 24 h light) on germination, suggesting that I. tinctoria is non-photoblastic. Germination decreased as salinity levels increased from 0 mM (96%) to 200 mM (4%), with no germination occurring at 250 or 400 mM. Similarly, as the osmotic potential decreased from 0 to -0.8 MPa, germination declined from 98 to 3%, respectively and ceased entirely at -1.0 MPa. In the pH experiment, the highest germination rate (99%) was obtained at pH 7, while the lowest (22%) was observed at pH 3. Seedling emergence was greatest (92%) for seeds buried at shallow depths (2 cm), decreasing to 6% at a depth of 6 cm, suggesting that soil tillage could be an effective strategy for reducing infestation. These findings provide valuable insights for developing integrated management strategies for I. tinctoria , offering new approaches for its effective control.