Comparing the emergence of Echinochloa crus-galli populations in different locations. Part II: similarities and threshold parameters

The variability in the emergence process of different populations was confirmedfor two Echinochloa crus-galli populations, one from Italy (IT) and the second fromNorway (NO). Seeds were sown in 12 localities over Europe and the Middle East, andthe emergence patterns of IT and NO were compared with those of several local populations at each location. Seeds of each population were sown in pots buried to theground level. The base temperature (Tb) for emergence was estimated by (1) analysinglogistic models applied to the field emergence of IT and NO, and (2) a germinationassay set in winter 2020 at constant temperatures (8, 11, 14, 17, 20, 26, 29°C) withnewly collected seeds in 2019 from the same fields where IT and NO had previouslybeen harvested in 2015. The logistic models developed for IT and NO in each locationshowed that the emergence pattern of IT was similar to that of the local populations inPoland, Italy, Spain, Turkey South and Iran, while NO fitted better to those in Swedenand Latvia. No germination was obtained for IT in a germination chamber, but theestimated Tb with the logistic model was 11.2°C. For NO, the estimated Tb was 8.8°Cin the germination chamber and 8.1°C in the field. Results suggest that adaptationto local environmental conditions has led to inter-population differences in Tb andparameter estimates of thermal-time models to predict the emergence of E. crus-gallishould only be used for populations with similar climatic and habitat conditions.