AOBPreview published online on July 15, 2008
Annals of Botany, doi:10.1093/aob/mcn115
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Published by Oxford University Press on behalf of the Annals of Botany Company 2008
Simulating the Influence of Vernalization, Photoperiod and Optimum Temperature on Wheat Developmental Rates
1 USDA-ARS, Agricultural Systems Research, 2150 Centre Avenue, Building D, Suite 200, Fort Collins, CO 80526, USA
2 USDA-ARS, Plant Physiology and Genetics Research Unit, US Arid Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85239, USA
3 Department of Plant Agriculture, University of Guelph, Guelph, Ontario N1G 1K1, Canada
4 New Zealand Institute for Crop & Food Research, Ltd, New Zealand
5 Punjab Agricultural University, Department of Plant Breeding, Ludhiana, Punjab, India
6 CIMMYT, Apdo. Postal 6–641, 06600 Mexico, D.F., Mexico
* For correspondence. E-mail Greg.McMaster{at}ars.usda.gov
Received: 21 February 2008 Returned for revision: 8 April 2008 Accepted: 12 June 2008
Background and Aims: Accurately representing development is essential for applying crop simulations to investigate the effects of climate, genotypes or crop management. Development in wheat (Triticum aestivum, T. durum) is primarily driven by temperature, but affected by vernalization and photoperiod, and is often simulated by reducing thermal-time accumulation using vernalization or photoperiod factors or limiting accumulation when a lower optimum temperature (Toptl) is exceeded. In this study Toptl and methods for representing effects of vernalization and photoperiod on anthesis were examined using a range of planting dates and genotypes.
Methods: An examination was made of Toptl values of 15, 20, 25 and 50 °C, and either the most limiting or the multiplicative value of the vernalization and photoperiod development rate factors for simulating anthesis. Field data were from replicated trials at Ludhiana, Punjab, India with July through to December planting dates and seven cultivars varying in vernalization response.
Key Results: Simulations of anthesis were similar for Toptl values of 20, 25 and 50 °C, but a Toptl of 15 °C resulted in a consistent bias towards predicting anthesis late for early planting dates. Results for Toptl above 15 °C may have occurred because mean temperatures rarely exceeded 20 °C before anthesis for many planting dates. For cultivars having a strong vernalization response, anthesis was more accurately simulated when vernalization and photoperiod factors were multiplied rather than using the most limiting of the two factors.
Conclusions: Setting Toptl to a high value (30 °C) and multiplying the vernalization and photoperiod factors resulted in accurately simulating anthesis for a wide range of planting dates and genotypes. However, for environments where average temperatures exceed 20 °C for much of the pre-anthesis period, a lower Toptl (23 °C) might be appropriate. These results highlight the value of testing a model over a wide range of environments.
Key words: Wheat, Triticum aestivum, T. durum, air temperature, thermal time, shoot apex, phenology, growth stages, anthesis, flowering
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