| S. bicolor (Moench.) BAC clones were selected from the TAMU sorghum BAC library after screening with twenty three PUC18 clones previously used to construct a sorghum RFLP map and two cDNA clones, one containing the sorghum alcohol dehydrogenase (adh) gene, and the other the maize shrunken-2 ;FISH of the selected BAC clones collectively marked 19 single-copy sites on seven different chromosomes. One marked chromosome D;BACs 22 B2 (45 Kb) and 128 H4 preferentially hybridized to centromeric regions. Moreover, hybridization was much stronger on 5 of the 10 pairs of S. bicolor chromosomes, providing extremely strong evidence that S. bicolor is tetraploid, with five chromosomes per set. Each set of five chromosomes can be termed a subgenome. Both, molecular recombinational mapping and physical mapping utilizing FISH of RFLP-selected BACs suggest that extensive rearrangement has occurred among the sorghum chromosomes following polyploidization. |
