Genome expression in polyploids is usually considered to be quite different depending on the genetic context. While it is admitted that autotetraploids resulting from polyploidization events within a species do not present major changes of genes expression, allotetraploid which result from hybridization between divergent species or lineage were showed to present very important changes of expression compared to the diploid (2x) parental lines (genomic shock). In this work, we investigated the citrus genome expression using Agilent microarrays in root of different couples of 2x and doubled diploid (4x): Poncirus, Cleopatra mandarin as well in the CLeopatra mandarin x Poncirus intergeneric hybrid. Gene expression is discussed in relation to the genetic status of the genotypes and the phenotypic differentiation observed between 4x parents, the 4x intergeneric hybrid and the 2x parents. (Texte intégral)