Résumé
After drynesses of the years 1970 and 1980, important means were deployed to create adapted cultivars to shorter rain season. The diffusion of these cultivars knew little success because unsuited to the interannual variability of the climate and the strategies deployed by farmers to take account it. The soudano-salian climate is characterized by an unimodale rain season whose beginning and end are extremely variable one year on the other. The frequential analysis of rain season structure with the Soil Balance Water model makes it possible to determine the beginning date and the completion date of season. Seventy rainfall stations distributed on the whole of the zone of rain agriculture of Mali were used. The photoperiodism of local varieties allows the plant to naturally adjust the duration of its cycle at the probable duration of rain season. A simplified Crop Growth model of photoperiodism sorghums allows expecting the date of flowering of some cultivars representative of the zone of rain agriculture. A cultivars is considerate adapted to an ecology if its flowering occurs in the 20 days which precede the completion date of rain season. The coupling of both models (Soil water Balance and of Crop Growth of the photoperiodic sorghums) within a Geographical Information System makes it possible to delimit for each cultivar its optimal zone of adaptation. The obtained maps represent a synthesis useful tool for the agronomists who wish to determine a possible diffusion area of cultivars. This result also allows the breeders to improve the definition of the adapted "ideal" cultivars and makes it possible to envisage deserting the concept of broad geographical adaptation by the search for specific adaptations to each ecology. (Résumé d'auteur)