Molecular diversity of CMS sources and fertility restoration in the genus: Helianthus

Abstract

Molecular characterization of 28 CMS sources and the fertile cytoplasm of H. annuus 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 differentiating 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 is followed for the isolation of 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. A bacterial artificial chromosome (BAC) library was constructed using the sunflower restorer line RHA325 and pBeloBAC11 as vector. The first sunflower BAC library corresponds to 1.7 haploid genome equivalents (104,736 clones average insert size approx. 50 kb). Use of STS markers, which had been developed from RAPD markers, allowed to identify three BAC clones by colony hybridization against high density filters. DNA fingerprinting using HindIII allowed to build a contig for the restorer locus Rf1.