Seed germination modeling of sterile oat biotypes susceptible and resistant to ACCase-inhibiting herbicides in response to temperature and drought stress

Temperature and water potential are the main determinants of the seed germination of plant species. Experiments were conducted to quantify the seed germination response of two sterile oat Avena sterilis subsp. ludoviciana (Durieu) Nyman biotypes susceptible and resistant to acetyl coenzyme A carboxylase inhibitor herbicides under six temperature regimes (5, 10, 15, 20, 25, and 30 °C), and five levels of drought stress (0.0,-0.3, -0.6, -0.9, and -1.2 MPa). The base temperature of seed germination in both biotypes was affected by drought stress. The base temperature changed from no stress to maximum stress in the susceptible biotype from 3.24 to 7.15 °C and in the resistant biotype from 3.12 to 7.43 °C. Thermal times required for 50% germination of the seed population at sub-optimal temperatures was increased from 26.2 to 87.8 °C day in the susceptible biotype and from 28.8 to 90.6 °C day in the resistant biotype. Increasing the temperature from 5 to 30 °C decreased the constant hydrotime from 10.92 to 1.66 MPa in the susceptible biotype and 11.52 to 1.98 MPa in the resistant biotype. The hydrothermal time constant for susceptible and resistant biotypes was 28.6 and 31.1 MPa. According to the hydrothermal time model, the herbicide-resistant biotype (-0.858 MPa) seeds require more water potential than the susceptible biotype (-0.905 MPa) to germinate at higher temperatures. Based on the parameters of the models, the germination response to temperature and water potential was similar in both susceptible and resistant biotypes. Consequently, maximum emergence of both biotypes is possible at 15 °C and without water stress conditions.