Following the difficulties encountered for assembling a 1.2 x sequencing of the highly heterozygous sweet orange genome, the International Citrus Genomic Consortium (ICOC) decided to estab1ish the first reference sequence of a whole nuclear citrus genome from a haploid Clementine. A saturated genetic linkage map of Clementine based on sequence-characterized markers was considered by the ICGC as an important too1 for genome sequence assemb1y. In this framework, CIRAD proposed to use an interspecific population C. maxima x C. clementina to implement the reference Clementine genetic map. A population of 250 hybrids of Chandler pummelo x Clementine was established in Corsica and 190 hybrids were used in this first phase of mapping. Collaboration was established between two French organizations (CIRAD and INRA), two groups from United States (UF-CREC and UCR), one Spanish institute (IVIA), INRA Morocco and Cukurova University from Turkey. Forty markers were found heterozygous in Clementine among a previous set of 90 SSR markers developed by CIRAD from microsatellite-enriched genomic libraries. With the objective to integrate the physical and genetic maps of Clementine, CIRAD and IVIA have developed new SSR markers from microsatellite sequences identified in BAC End Sequences (BES) of diploid Clementine. On hundred and 10 of these new markers were found heterozygous for Clementine or Chandler pummelo and were used for genotyping. INRA France deve1oped 500 SSR markers from ESTs databases and found 170 markers heterozygous for Clementine. INRA Morocco contributed to the genotyping of 112 SSR markers developed from EST databases and genomic libraries, while 50 ESTs SSR were analysed by Cukurova University. SSR markers mainly developed from EST databases and already mapped for sweet orange were genotyped by UF-CREC (70 markers) and UCR (60 markers) to allow comparisons among the C. sinensis. C. maxima and C. c1ementina maps. lndeed, taking advantage of the important allelic d