Photoperiod and vernalization effect on anthesis date in winter-sown spring wheat regions

Accurate prediction of phenology is required to guide crop management decisions and to predict crop growth and yield. However, the relative importance of photoperiod and vernalization in predicting anthesis dates for spring bread and durum wheat (Triticum aestivum L. and T. durum Desf.) sown in the winter has not been reported. The purpose of this research is to determine the improvement in predicting anthesis dates of spring wheat sown in the winter when photoperiod and vernalization are considered. Observed dates of anthesis were obtained from University of Arizona wheat variety trials conducted at Maricopa, Wellton, and Yuma, AZ. The Cropping Systems Model CROPSIM-CERES as released in DSSAT 4.5 was used to simulate days to anthesis based on temperature, daylength, and vernalization. For 12 bread and durum wheat cultivars, the model predicted days to anthesis with a root mean square error (RMSE) of 7.6 d if all cultivar differences were ignored, 6.4 d considering only differences in thermal time (TT), 6.1 d with differences in TT and daylength response, 6.4 d with TT and vernalization, and 6.2 d with TT, daylength, and vernalization. Consideration of cultivar differences in TT and photoperiod response improved the prediction of days to anthesis for winter-sown spring wheat, but there was no benefit from considering effects of vernalization in CROPSIM-CERES.