Phylogenetic relationships of the sorghum genus

To determine the phylogenetic relationships within the Sorghum genus, the internal transcribed spacer 1 (ITS1) region of the twenty-five species were sequenced. The length of the ITS1 was 273bp to 274bp, with GC content ranging from 55.7% to 65.9%. Parsimony analysis revealed two main groups within the Sorghum genus, with close relationships between the cultivated S. bicolor and five Australian native species, with one showing no difference in ITS1 sequence. These Australian native species are phenotypically very diverse, with their relationships to the cultivated species much closer than previously thought. Recent research has shown that microsatellites (SSRs) specific for one species can be amplified in related species. To establish whether S. bicolor specific primers amplify product in the wild species, twenty microsatellite markers were screened across the twenty-four wild Sorghum species. Twelve markers amplified product in at least 6 wild species, with two markers able to amplify product in all Sorghum species. Most of the markers were amplified within their expected size range, however in some wild species the markers were present in multiple copies, potentially at homologous loci. The co-dominant nature of microsatellite markers was shown by confirming the hybrid nature of two crosses between S. bicolor and the wild species S. drummondii and S. purpureosericeum. The new genetic information on the wild Sorghum species will facilitate the assessment and maintenance of their biodiversity, and in utilising wild species in conventional sorghum breeding programs.