|Gulya Jr, Thomas|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/4/2007
Publication Date: 1/10/2007
Citation: Feng, J., Seiler, G.J., Gulya, T.J., Jan, C.C. 2007. Advancement of pyramiding new Sclerotinia stem rot resistant genes from H. californicus and H. schweinitzii into cultivated sunflower. 5th Annual Sclerotinia Initiative Meeting, January 17-19, 2007, Bloomington, MN. p. 13. Interpretive Summary:
Technical Abstract: Sclerotinia is a major disease in cultivated sunflower across the world and the present-day sunflower hybrids are considered lacking high resistance to Sclerotinia. In general, wild Helianthus species are known to possess a much wider genetic variability than that of the cultivated sunflower for Sclerotinia stem rot resistance. An abundance of wild Helianthus accessions have been evaluated as potential sources for Sclerotinia stem rot resistance with the perennial species having been found to be highly resistant, especially the higher ploidy level species. Interspecific hybridization of perennial hexaploid species H. californicus and H. schweinitzii with HA 410 were conducted in 2006 based on the BC1F1's obtained in 2005. In total, 109 BC1F1 plants were grown in the greenhouse for backcrossing. The backcross BC1F1 progenies were triploids with a 2n chromosome number of around 51. Because of the unbalanced chromosome number in the triploid BC1F1, the BC1F1 pollen fertility ranged from 2.45% to 4.63%, and seed set was very low. In total, 59 BC2F1 seeds were obtained from 136,220 pollinated florets. After germination, only 24 BC2F1 plants were established with a chromosome numbers of 2n=40 to 49, and a pollen stainablity of 34.2%. Based on these results, we are re-crossing the BC1F1 with HA 410 to produce more BC2F1 seeds to screen for resistance individuals. Our results clearly demonstrated that the major obstacle in interspecific gene transfer between hexaploid perennials and cultivated sunflower is the BC1F1 generation, with a chromosome number of 2n=51. We would strongly suggest using the embryo rescue technique to improve the establishment of the BC2F1 seedlings. Presently, we are crossing additional BC1F1 plants with HA 410 and culturing the BC2F1 embryos. We expect to produce a large population of BC2F1 progenies to provide a better foundation for further backcrosses as we approach the base 2n=34 chromosome of the recurrent parent HA 410. Identification of resistant progenies will be initiated as early as the BC3F1 or BC4F1 generation.