A comparison of cardinal temperatures between haloxyfop R methyl ester- resistant and susceptible winter wild oat (Avena ludoviciana Durieu.) biotypes

Evolution of resistance in weeds leads to induction of fitness cost. Five winter wild oat biotypes resistant to haloxyfop R methyl ester collected from Kalaleh Township located in Golestan province were evaluated along with the susceptible biotype in terms of variation in cardinal temperatures in the following study. The experiment was conducted at laboratories of Gorgan University of Agricultural Sciences and Natural Resources as completely randomized design with 4 replications each consisting of 25 seeds. Petri dishes containing seeds were incubated and monitored continuously at temperatures 5-40 °C (at 5°C intervals) following a 72 hours vernalization at 4°C. Non-linear regression models were used to quantify germination response to temperature. No notable difference was observed among winter wild oat biotypes and beta model at 50 percentile was the most suitable model to describe cardinal temperatures. Base, optimum and ceiling temperatures were estimated between -4.21 to -5.91, 23.37-23.94 and 36.99-37.54 °C, respectively. Thermal tolerance range of susceptible and resistant biotypes were not significantly different. Susceptible and resistant biotypes showed similar response. Lack of fitness cost regarding cardinal temperatures demonstrates that similar non-chemical management practices including early sowing may be implemented to control resistant and susceptible biotypes germination and emergence