Résumé
Most modem sugarcane cultivars are complex aneuploid polyploid clones derived from two ancestral species, Saccharum officinarum (presumably 2n=80 and x=10) and S. spontaneum (presumably 2n=40-128 and x=8). We are focussing on cultivar R570 (CERF, Reunion). R570 has about 115 chromosomes; GISH revealed up to 12 whole chromosomes originating from S. spontaneum and 11 S. officinarum/S. spontaneum recombinant chromosomes, the rest being whole chromosomes originating from S. officinarum (D'Hont et al, 1996, MGG250:405-413). RFLP analysis of individuals derived from selfing of the cultivar allowed construction of a first map (Grivet et al, 1996, Genetics 142:987-1000). Inheritance appeared essentially polysomic. The two genomic components showed general colinearity and several products of interspecific crossingover were observed. The 96 cosegregation groups detected could be assembled into 10 linkage groups based on homology. This map revealed global colinearity with our current sorghum map (Dufour et al, in press, TAG). We are now using the sorghum map in order to select heterologous probes for filling the gaps of the sugarcane map. This strategy already led to the fusion of two pairs of previously separate linkage groups and to the coverage of two new linkage groups. Sorghum is thus confirmed as an excellent diploid reference for sugarcane. AFLPs were also found efficient as a complementary source of single dose markers. The map now has 573 RFLP markers derived from 166 probes, 2 isozyme markers and 100 AFLP markers. Another 204 segregating markers remain unlinked, probably characterizing the less polymorphic S. officinarum part of the genome. (Texte intégral)