A MOLECULAR APPROACH TO UNRAVELING THE GENETICS OF SUGARCANE, A COMPLEX POLYPLOID OF THE ANDROPOGONEAE TRIBE

Modern sugarcane varieties are complex aneuploids and typically have c hromosome numbers in the 100-125 range with about 5-10% of them contri buted by wild relatives, mainly Saccharum spontaneum, and the rest by S. officinarum. This particular genomic constitution was found favorab le for mapping the S. spontaneum genome, using maize as a diploid refe rence for comparison. We conducted an analysis of 32 individuals deriv ed from the selfing of variety SP 701006 using four isozymes and 53 ma ize probes which covered the whole maize genome. A total of 348 segreg ating bands were generated. Highly significant cosegregations enabled us to place 94 markers into 25 cosegregation groups. Eighteen of these groups involved S. spontaneum specific markers and might therefore ma rk S. spontaneum chromosomes in segregation. On the basis of probes in common, the 25 cosegregation groups could be assembled into eight ten tative linkage groups, of which seven describe S. spontaneum chromosom es. A large degree of synteny between sugarcane and maize could be inf erred, with a much lower rate of recombination in sugarcane.