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 (۵, ۱۰, ۱۵, ۲۰, ۲۵, and ۳۰ °C), and five levels of drought stress (۰.۰,-۰.۳, -۰.۶, -۰.۹, and -۱.۲ 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 ۳.۲۴ to ۷.۱۵ °C and in the resistant biotype from ۳.۱۲ to ۷.۴۳ °C. Thermal times required for ۵۰% germination of the seed population at sub-optimal temperatures was increased from ۲۶.۲ to ۸۷.۸ °C day in the susceptible biotype and from ۲۸.۸ to ۹۰.۶ °C day in the resistant biotype. Increasing the temperature from ۵ to ۳۰ °C decreased the constant hydrotime from ۱۰.۹۲ to ۱.۶۶ MPa in the susceptible biotype and ۱۱.۵۲ to ۱.۹۸ MPa in the resistant biotype. The hydrothermal time constant for susceptible and resistant biotypes was ۲۸.۶ and ۳۱.۱ MPa. According to the hydrothermal time model, the herbicide-resistant biotype (-۰.۸۵۸ MPa) seeds require more water potential than the susceptible biotype (-۰.۹۰۵ 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 ۱۵ °C and without water stress conditions.

Keywords:

Cardinal temperatures , Fitness cost , Hydrothermal time , Quantification , Water potential