Résumé
The fit of rice genotypes and copping calendars into an agro-ecological niche is largely a function of hydrology and the thermal environment. Although rice can be grown in very diverse climates, a given genotype has a narrow band of thermal adaptation. The most sensitive processes are development per se and reproduction, namely the microspore stage (chilling) and anthesis (heat). The crop-generated microclimate must be taken into account because organ temperature can differ greatly from ambient temperature. A multi-environment study in Senegal (hot-dry and cool-dry seasons), Philippines and southern France was conducted to observe and model microclimate (water, canopy and panicle temperatures, the latter by IR imagery), phenology, the flowering period, time of day of anthesis (TOA) and spikelet sterility. Water and panicle temperatures differed strongly from air temperature, both being by up to 10°C colder than air at midday under dry atmospheric conditions. TOA occurred in the morning or early afternoon, depending on night temperature and VPD, but had a constant duration of 2 h. The plasticity of TOA was adaptive because it helped anthesis escape from very hot or very cold conditions. Together, transpiration cooling (heat avoidance) and plasticity of TOA (temporal escape) constitute powerful coping mechanisms in rice for extreme temperatures. The simple crop model RIDEV V2 (V1 was a simpler tool in the 90s) was developed to predict phenology and thermal sterility of rice while taking into account microclimate. RIDEV can be used as a predictive tool for agronomy and agro-ecology (e.g. climate-change impacts), but is also equipped with a powerful parameter-optimization tool for reverse modeling approaches (heuristics). The latter was applied to phenotype phenological traits (photothermal constants of genotypes) for 230 diverse rice accessions studied in Senegal and Madagascar in the ORYTAGE (Diversité des caractères d'adaptation aux contraintes hydriques et thermiques chez le riz) project. Future uses of RIDEV in rice genetics and agronomy are discussed in the paper, namely for phenotype- genotype association studies (reverse mode) and mapping of climate-change impacts on the rice crop (forward mode). (Résumé d'auteur)