Considering climatic changes, improving crops for drought tolerance is one of the major challenges of plant breeders for the coming years. During domestication and selection events of major food crops in different eco-geographical environments, humankind has generated some selection pressure acting on key adaptive genes that could be still useful for crop improvement. Generation Challenge Program has funded in 2006 - 2008 a commissioned project called "allelic diversity of orthologous candidate genes" (ADOC) aiming to assess the allelic diversity of candidate genes or gene families for drought tolerance, in reference collections of about 300 accessions of seven mandate crops of the CGIARs (rice, barley, sorghum, bean, chickpea, potato and cassava). Here we report results obtained on rice for several genes families, including ASR (ABA-stress ripening), ERECTA and SuSy (sucrose synthase) genes, involved at different steps of drought stress response. A detailed analysis of nucleotide polymorphism from aligned DNA sequences, representing total or partial coding and non coding regions of the different genes studied, reveal different diversity patterns within gene families. Several genes present evidence of selection acting on specific subgroups of this germplasm collection. Implications in term of plant adaptation, domestication and use in plant improvement for drought tolerance will be discussed.