The origin of limes and lemons has been a source of conflicting taxonomic opinions. Cultivated Citrus species certainly resulted from interspecific hybridization between four basic taxa (C. reticulata; C. maxima; C. medica and C. micrantha). However, the origin of most lemons and limes remains controversial. We studied the maternal phylogeny and nuclear structure of 133 Citrus accessions. The lime and lemon horticultural group is highly polymorphic with diploid, triploid and tetraploid varieties. It results from many independent reticulation events defining genetic subgroups. All these limes and lemons genetic subgroups are highly heterozygous with interspecific admixture of two, three and even four ancestral taxa genomes for some triploid varieties. C. medica contributed to all limes and lemons and was the direct male parent for the main subgroups in combination with C. micrantha, C. reticula, C. aurantium or C. maxima x C. reticulata hybrid. Among triploid imes, C. latifolia accessions (Tahiti type) result from the fertilization of a haploid ovule of C. limon by a diploid gamete of C. aurantifolia. As limes and lemons were vegetatively propagated the intra-subgroup phenotypic diversity results from asexual variations. (Texte intégral)