Temperature-dependent germination dynamics of herbicide-resistant and susceptible blackgrass (Alopecurus myosuroides) and silky windgrass (Apera spica-venti) from Poland

Herbicide-resistant grass weeds, including blackgrass (Alopecurus myosuroides Huds.) and silky windgrass (Apera spica‑venti (L.) P.Beauv), pose an escalating challenge to sustainable cereal production in Europe. This study examined temperature‑dependent germination dynamics of herbicide‑resistant (HR) and susceptible (S) biotypes of both species collected from Polish agroecosystems. Germination was tested under five temperatures: constant 5, 10, 15, and 20 °C, and alternating 15/5°C. Resistance groups were evaluated using the area under the germination curve (AUC), a cumulative measure that integrates both the speed and extent of germination. In both species, temperature strongly modulated germination dynamics. Multiple‑resistant blackgrass biotypes exhibited higher germination rates at certain temperatures, suggesting distinct physiological responses among resistance types rather than uniform adaptation across temperature ranges. Conversely, multiple-resistant silky windgrass biotypes (e.g., M1235) germinated vigorously at 5 °C. Still, they declined at warmer temperatures, achieving the highest AUC at 5 °C but the lowest at 20 °C (a difference exceeding 74 units), suggesting a temperature-specific shift in dormancy release or germination physiology. Susceptible groups germinated more slowly and consistently across temperatures. These contrasting thermal responses reveal that herbicide-resistant populations can exploit different temperature niches, potentially influencing their emergence timing and competitive ability in the field. Understanding these patterns is essential for developing climate-adapted, resistance-aware weed management strategies, including optimized sowing schedules and integrated, non-chemical control measures.