|OTTMAN, MICHAEL - University Of Arizona|
|HUNT, L - University Of Guelph|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2012
Publication Date: 4/19/2013
Citation: Ottman, M.J., Hunt, L.A., White, J.W. 2013. Photoperiod and vernalization effect on anthesis date in winter-sown spring wheat regions. Agronomy Journal. 105(4):1017-1025.
Interpretive Summary: Accurate predictions of time of flowering and maturity can greatly assist producers in making decisions on crop management, leading to higher yields and reducing input use. Extension services and farm advisors often use simple models to predict flowering that only consider the effects of temperature on crop development. Flowering time of wheat is also influenced by daylength and by a response to low temperature called "vernalization," wherby a plant has to experience low temperatures in order to flower. Modern spring wheats are thought to have little or no response to daylength and vernalization, but it was hypothesized that considering one or both factors might improve predictions of flowering time for spring bread and durum wheats grown as winter annuals, as commonly done in Arizona and California. Measured data on flowering of wheat cultivars were obtained from University of Arizona wheat varity wheat variety trials conducted at Maricopa, Wellton, and Yuma, AZ. A computer model called "The Cropping Systems Model CROPSIM-CERES" was used to simulate flowering dates based on air temperature, daylength, and vernalization response. For 12 bread and durum wheat cultivars, the best accuracy was obtained when cultivar differences in daylength response were considered. Including and effect of vernalization bought no benefit. The estimated accuracy considering just temperature was 7.6 days vs 6.1 days with cultivar differences in temperature and daylength responses. These results should be directly applicable to prediction of time of flowering for wheat producers in Arizona and California, allowing them to manage crops with greater precision.
Technical Abstract: 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.) grown as a winter annual has not been reported. The purpose of this research is to determine the improvement in predicting anthesis dates of spring wheat grown as a winter annual 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 preducted 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 for the current range of sowing dates (early December to mid-January), there was no benefit from considering possible effects of vernalization.