Résumé
Besides the production of an embryonic primary root, rice mainly produces different kinds of post-embryonic roots that have different ontological origins and differentiation fates. Indeed, rice produces crown roots from the stem and two kinds of lateral roots from the existing roots: the large lateral roots and the small lateral roots. All of them possess different radial differentiation, growth capacities, and gravitropism sensitivity. Rice, being an important cereal crop, was adopted by the scientific community as a model plant. Consequently, several tools and resources were developed such as mutant libraries, an agrobacterium-mediated transformation procedure, transcriptomic databases, and genomes of thousands of varieties were sequenced to perform genome-wide association studies. This supported the identification and functional study of genetic determinants involved in rice root formation. Thanks to the data obtained over the last decade, the discovery of conserved and specific genetic elements governing the formation of the different types of roots has been initiated. This opens the prospect of better understanding how these branching processes have evolved within the same species to produce different types of roots and between species compared to what is known of these processes in other plants. This chapter overviews the main hormonal and genetic elements involved in the control of different post-embryonic root development events in rice, stressing the similarities and the specificities leading to the creation of these distinct root axes in rice.