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Title: Reconciling Alternative Models of Phenological Development in Winter Wheat

Author
item JAMIESON, P - NEW ZEALAND
item BROOKING, I - NEW ZEALAND
item SEMENOV, M - ENGLAND
item McMaster, Gregory
item White, Jeffrey
item PORTER, J - KVL,DENMARK

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2007
Publication Date: 6/6/2007
Citation: Jamieson, P.D., Brooking, I.R., Semenov, M.A., Mcmaster, G.S., White, J.W., Porter, J.R. 2007. Reconciling Alternative Models of Phenological Development in Winter Wheat. Field Crops Research.103:36-41.doi:10.1016/j.fcr.2007.04.009.

Interpretive Summary: Accurately representing development is essential for applying crop simulation models to investigate changes in climate, varieties, or crop management. Development in wheat (Triticum aestivum , T. durum) is primarily driven by temperature (i.e., thermal time), but affected by vernalization and photoperiod. The influence of climate, genotype, and management is often simulated by reducing thermal time accumulation by vernalization or photoperiod factors or when an optimum temperature (Topt) is exceeded. We examined different values of Topt (15, 20, 25, and 50oC) and methods for applying vernalization and photoperiod factors (either the most limiting or the multiplicative value of the vernalization and photoperiod development rate factors) for predicting anthesis predictions across a broad range of planting dates and genotypes. Simulated results were compared to observed field data from Ludhiana, Punjab, India with July through December planting dates and seven cultivars varying in vernalization response. Simulating anthesis was similar for Topt values of 20, 25, and 50oC, but a Topt of 15oC resulted in a consistent bias towards predicting anthesis late for early planting dates. Results for Topt above 15oC may have occurred because mean temperatures rarely exceeded 20°C before anthesis for many planting dates. For cultivars having vernalization requirements, anthesis was more accurately simulated when vernalization and photoperiod factors were multiplied rather than using the most limiting of the two factors. Setting Topt 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 with temperatures above 20°C for much of the pre-anthesis period, possibly a lower Topt (23°C) is appropriate. This highlights the need to test models over a wide range of environments before applying them to climate change and other problems.

Technical Abstract: • Background and Aims Accurately representing development is essential for applying crop simulation models to investigate changes in climate, genotypes, or crop management. Development in wheat (Triticum aestivum , T. durum) is primarily driven by thermal time, but affected by vernalization and photoperiod. The influence of climate, genotype, and management is often simulated by reducing thermal time accumulation by vernalization or photoperiod factors or when an optimum temperature (Topt) is exceeded. We examined Topt and methods for applying vernalization and photoperiod factors for anthesis predictions across a broad range of planting dates and genotypes. • Methods We examined Topt values of 15, 20, 25, and 50oC and either the most limiting or the multiplicative value of the vernalization and photoperiod development rate factors for simulating anthesis. Field data were from Ludhiana, Punjab, India with July through December planting dates and seven cultivars varying in vernalization response. • Key Results Simulating anthesis was similar for Topt values of 20, 25, and 50oC, but a Topt of 15oC resulted in a consistent bias towards predicting anthesis late for early planting dates. Results for Topt above 15oC may have occurred because mean temperatures rarely exceeded 20°C before anthesis for many planting dates. For cultivars having vernalization requirements, anthesis was more accurately simulated when vernalization and photoperiod factors were multiplied rather than using the most limiting of the two factors. • Conclusions Setting Topt 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 with temperatures above 20°C for much of the pre-anthesis period, possibly a lower Topt (23°C) is appropriate. This highlights the need to test models over a wide range of environments before applying them to climate change and other problems.