Plant & Animal Genome VI Conference Plant & Animal Genome VI Conference
W48
Introgression with wild relatives plays a major role in sugarcane breeding. Present sugarcane cultivated clones (Saccharum spp. 2n = 100 to 130) are derived from interspecific hybridizations between the sugar producing species, S. officinarum, and wild relatives, mainly S. spontaneum. We are using DNA in situ hybridization to investigate the complex genome structure of sugarcane cultivars. The rDNA sites have been located by in situ hybridization in the main species of the Saccharum genus. The results support a basic chromosome numbers of 10 for S. officinarum and S. robustum and 8 for S. spontaneum and provide a first bridge between physical and genetic mapping. Using genomic DNA in situ hybridization, we showed the possibility of distinguishing the chromosomes contributed by the species S. officinarum and S. spontaneum in sugarcane cultivars and, contradicting previous assumptions, demonstrated the occurence of chromosome exchange between these two species. Characterisation of S. spontaneum contribution to cultivars from various temperate/sub-tropical and tropical origins is curently in progress. In the cultivar R570 and NCo 376, we identified about 10% and 22% of whole chromosomes contributed by S. spontaneum, respectively, and about 10% of chromosomes derived from exchanges between the two species S. officinarum and S. spontaneum. Investigating the genome structure of S. barberi using genomic in situ hybridization, we could identify two groups of chromosomes derived from S. officinarum and S. spontaneum illustrating the interspecific origin of this taxonomical group.