Abstract
The advent of bacterial artificial chromosomes (BACs) and development of high quality methods for fluorescent in situ hybridization (FISH) to plant chromosomes offer revolutionary tools for plant genome analysis. We discovered a 45 kb sorghum BAC (22B2) that differentially hybridizes to centromere regions of 10 of the 20 chromosomes of sorghum (Sorghum bicolor). Moreover, hybridization of this BAC to plants trisomic (2n = 20 + 1) for the five available trisomes identified their respective subgenomic affiliations. Plants trisomic for chromosomes E, H, and I displayed 11 signals, indicating that these chromosomes are in the subgenome marked by the BAC-FISH signal, whereas plants trisomic for chromosomes D and G had only 10 signals and therefore belong to the subgenome not displaying the FISH signals. The results provide strong evidence that sorghum is at least of tetraploid origin, and that there are two subgenomes of five chromosomes each in the S. bicolor genome.