In this study, we evaluated arbuscular mycorrhizal fungi inoculation effect on three durum wheat cultivars grown under well-watered and post heading water deficit conditions. Inoculation improved water use efficiency and drought tolerance. This improvement was shown by a lower proline content, and an increase in the following parameters as soluble sugars content, leaf area development, relative water content, leaf specific weight, root and shoot biomass, spike fertility, and grain yield. Response to inoculation varied by genotype, suggesting a genotypic effect which is involved in root colonization and inoculation response, and may play an important role in maximizing plant profit from this symbiosis. In this study, root colonization was proportional to inoculation response that could be used as a selection index for a better cultivar-inoculum combination to maximize durum production under water stress conditions.