Résumé
A large sugarcane EST project recently gave us access to 261,609 sugarcane EST sequences assembled into 81,223 clusters. Among them, we identified 88 resistance gene analogs (RGAs) based on their homology with typical pathogen resistance genes using a stringent BLAST search with an expect value of e-50. They included representatives of the three groups of resistance genes with NBS/LRR, LRR or S/T KINASE domains. Fifty RGAs revealed a total of 148 single dose polymorphic RFLP markers that could be located on the sugarcane reference genetic map (cultivar R570, 2n=ca 115). Fifty-five SSR loci corresponding to 134 markers in R570 were also mapped to enable the classification of the various haplotypes into homology groups. Several RGA clusters were found. One cluster of two LRR-like loci mapped close to the only disease resistance gene known so far in sugarcane, that confers resistance to common rust. Detailed sequence comparison between two NBS/LRR RGA clusters in relation to their orthologs in rice and maize suggests their polyphyletic origins and indicates that the divergence between sugarcane paralogous RGAs can be larger than the divergence with an orthologue in a distant species. (Texte intégral)