Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2005
Publication Date: 10/25/2005
Citation: Kuhlman, L., Price, H.J., Burson, B.L., Rooney, W.L., Stelly, D.M. 2005. Interspecific hybrids in the genus Sorghum [abstract]. American Society of Agronomy. Paper No. 48-4. Interpretive Summary:
Technical Abstract: Grain sorghum [Sorghum bicolor (L.) Moench] has been improved by public and private breeding programs utilizing germplasm mostly from within the species. Limited genetic resources within the section Eu-Sorghum, containing S. bicolor, S. propinquum, and S. halapense, have been utilized. Genetic resources beyond the Eu-Sorghum section, 21 species in 4 sections, have never been used because of cross-incompatibilities between the wild species and S. bicolor. Overcoming these incompatibilities would provide valuable new genetic resources for continued improvement. By crossing an accession of S. bicolor (2n=20) containing the iap allele, which allows pollen tube growth of foreign species, with S. macrospermum (2n=40), 20 interspecific hybrids were recovered. These hybrids were intermediate to the parents in chromosome number (2n=30) and overall morphology. Meiosis in both parents was regular; S. bicolor had 10 bivalents per pollen mother cell (PMC) and S. macrospermum had an average of 19.89 bivalents per PMC. Six hybrids were studied cytologically and meiosis was irregular with the chromosomes associating primarily as univalents and bivalents. There was an average of 3.54 bivalents per PMC, with a range of 0-8 bivalents, most of which were rods (98%). These bivalents cannot be attributed to autosyndesis because of the absence of quadrivalents in the parents and thus the pairing is likely between members of S. bicolor and S. macrospermum genomes. Pollen stainability was very low with only 5 fully stained pollen grains observed in approximately 20,000 examined, indicating normal gametic formation is rare. However, backcrosses onto cytoplasmic male sterile S. bicolor, using pollen from the interspecific hybrid, resulted in 14 putative BC1F1 plants. The production of backcrosses indicates that genomic introgression of S. macrospermum into S. bicolor is possible. This research could open the door for introgression of important alleles from wild relatives into cultivated sorghum.