Low-temperature tolerance in cereals: Model and genetic interpretation

Exposure of plants to low temperature (LT) produces a myriad of measurable changes in morphological, biochemical, and pbysiological characters that ar e often highly correlated with plant cold tolerance. These complicated resp onses have made it difficult to separate cause-and-effect adjustments to LT , emphasizing the need for a descriptive framework for the integration of c urrent knowledge so that research efforts can be better focused. The object ive of this study was to construct a functional model that complies with th e known LT responses of cereals so production risks, cause-and-effect proce sses, and genetic theories can be systematically investigated. In the model , a series of equations describe acclimation, dehardening, and damage due t o LT stress. A modular design permits modification and allows the model to be interfaced with other simulation models that input or compute daily meas urements of soil temperature and phenological development. LT tolerance is estimated on a daily basis relative to phenological stage and the input of a genetic coefficient is required. Operation of the model is consistent wit h recent interpretation of LT-gene regulation and it is especially sensitiv e to the switching signals that down-regulate LT-gene expression in plants maintained for long periods of time in the optimum temperature range far co ld acclimation Simulation studies have also shown that small differences in cultivar genetic potential translate into large differences in LT toleranc e when the cumulative effects of LT stress enter the critical range for ove rwinter survival. The model has been field validated for cereals overwinter ed in Saskatchewan, Canada, but it also has potential application in the si mulation of LT responses of a wide range of species and climates.