MOLECULAR CHARACTERIZATION OF CMS SOURCES AND THEIR FERTILITY RESTORATION IN THE GENUS Helianthus

¹ Institut für Pflanzenbau und Pflanzenzüchtung I, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany

² Department of Genetics, Biochemistry and Life Science Studies, Clemson University, 100 Jordan Hall, Clemson, SC 29634-0318, USA

Molecular characterization of 28 CMS sources and the fertile cytoplasm in sunflower demonstrated that cytoplasms different by their origin show a considerable similarity that cannot be expected from their pedigree. Cluster analysis using the UPGMA method allowed differentiation of 10 mitochondrial (mt) types based on RFLP data. Characteristic proteins specific for one or more CMS sources could be identified, which correspond to the mt types. In addition, the data obtained on fertility restoration for a subset of nine new CMS sources support the classification of the cytoplasms made on mtDNA level as demonstrated in the UPGMA dendrogram. A map-based cloning approach was followed for isolating the restorer gene Rf1, which restores pollen fertility in hybrids based on PET1. Markers closely linked to the restorer gene could be identified using AFLP and RAPD technologies. The map for the linkage group carrying the restorer gene now consists of 43 markers (7 RAPD-, 1 SSR-, and 35 AFLP-markers) and covers 191.9 cM. Two of the RAPD markers, OPK13_454 and OPY10_740, were successfully converted into SCAR markers, HRG01 and HRG02, which are now available for marker-assisted selection. The SCAR markers were tested in a set of 11 restorer and nine maintainer lines of PET1. For cloning the restorer gene Rf1, colony hybridizations against high density BAC filters of our sunflower BAC library and 3D-PCR pooling strategies were used to identify positive BACs. BAC fingerprinting using different restriction enzymes in combination with hybridizations was performed to develop a contig around the restorer locus Rf1.