Mapping of the New Fertility Restorer Gene Rf-PET2 Close to Rf1 on Linkage Group 13 in Sunflower ( Helianthus annuus L.).

The PET2-cytoplasm represents a well characterized new source of cytoplasmic male sterility (CMS) in sunflower. It is distinct from the PET1-cytoplasm, used worldwide for commercial hybrid breeding, although it was, as PET1, derived from an interspecific cross between Helianthus. petiolaris and H. annuus . Fertility restoration is essential for the use of CMS PET2 in sunflower hybrid breeding. Markers closely linked to the fertility restorer gene are needed to build up a pool of restorer lines. Fertility-restored F1 -hybrids RHA 265(PET2) × IH-51 showed pollen viability of 98.2% ± 1.2, indicating a sporophytic mode of fertility restoration. Segregation analyses in the F2 -population of the cross RHA 265(PET2) × IH-51 revealed that this cross segregated for one major restorer gene Rf-PET2 . Bulked-segregant analyses investigating 256 amplified fragment length polymorphism (AFLP) primer combinations revealed a high degree of polymorphism in this cross. Using a subset of 24 AFLP markers, three sequence-tagged site (STS) markers and three microsatellite markers, Rf-PET2 could be mapped to the distal region of linkage group 13 between ORS1030 and ORS630. Three AFLP markers linked to Rf-PET2 were cloned and sequenced. Homology search against the sunflower genome sequence of HanXRQ v1r1 confirmed the physical location of Rf-PET2 close to the restorer gene Rf1 for CMS PET1. STS markers were mapped that can now be used for marker-assisted selection.