Sugarcane Allelic Variation: What Does It Tell About Polyploidization

Modern sugarcane cultivars (Saccharum spp.) are highly polyploid and aneuploid. They were initially derived from interspecific crosses between Saccharum officinarum (domesticated sugar accumulating species; 2n= 8x=80) and Saccharum spontaneum (more vigorous wild species; 2n = 5x = 40 to 16x = 128) which are two of the six polyploidy species forming the Saccharum genus. The polyploidization processes that shaped the genomes of these species and the extent to which these genomes diverged still need to be better defined. One approach to get new insight into this issue is to investigate into detail the range of intra- and inter-specific polymorphism (haplotypes) at specific nuclear loci. To this end, we sequenced and analyzed homo/homeologous BACs carrying one of the single nuclear genes TOR Kinase (Target of Rapamycin); PHY C (Phytochrome C) or LEAFY (LFY) from the Saccharum spp. R570 and SP80-3280 cultivars. Selected small exons and introns from these genes were sequenced from the Saccharum species to evaluate haplotype divergence. In addition, to broaden up our analysis, a similar approach was undertaken for a set of small putative single nuclear genes.The data should help in improving our knowledge on genome architecture and evolution of Saccharum species.