Functional integrated genetic linkage map based on EST-markers for a sugarcane (Saccharum spp.) commercial cross

The growing availability of ESTs provides a potentially valuable source of new DNA markers. The authors examined the SUCEST database and developed EST-derived markers. Thus to enhance the resolution of an existing linkage map and to identify putative functional polymorphic gene loci in a sugarcane commercial cross, 149 EST-SSRs and 10 EST-RFLPs were screened in the SP80-180 x SP80-4966 mapping population. With the markers already analyzed in the previous map, 2303 polymorphic markers were generated, of which 1669 (72.5%) were single-dose (SD) markers. Out of these 1669 SD markers, 664 (40%) were scattered onto 192 co-segregation groups (CGs) with a total estimated length of 6.261,1 cM. Using both genomic and EST-derived SSR and RFLP markers, 120 out of the 192 CGs were formed into fourteen putative homology groups (HGs). The EST-derived markers were subjected to BLASTX search in the SUCEST database, of which putative function was assigned to 113 EST-SSRs and six EST-RFLPs based on high nucleotide homology to previously studied genes. The integration of EST-derived markers improved the map, making it possible to consider additional fine mapping of the genome, and providing the means for developing 'perfect markers' associated with key QTL. To summarize, this paper deals with the construction of a genetic linkage map of sugarcane that is populated by functionally associated markers.