Abstract
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.
Highlights
Cytoplasmic male sterility (CMS) is a maternally inherited trait in higher plants, in which these plants fail to develop or shed functional pollen
The results clearly showed that cytoplasmic male sterility (CMS) PET2 is different from CMS PET1 and could represent an interesting alternative for commercial hybrid breeding
The segregating progeny of a cross between the CMS line RHA 265(PET2) and the restorer line IH-51 was evaluated for male fertility/sterility to determine the number of genes involved in fertility restoration
Summary
Cytoplasmic male sterility (CMS) is a maternally inherited trait in higher plants, in which these plants fail to develop or shed functional pollen. Fertility restoration by dominant nuclear restorer genes is essential to produce fully fertile F1 -hybrids that allow exploitation of CMS/Rf-systems for commercial hybrid breeding [3]. Only one CMS system, the so called PET1-cytoplasm, has so far been used for commercial hybrid breeding [4], more than 70 CMS sources have been described [5]. The lack of restorer lines and molecular markers closely linked to the restorer genes has hampered the use of the new CMS sources as well as the development of new restorer and maintainer pools for these cytoplasms. An interest exists for introducing new CMS cytoplasms into commercial sunflower breeding
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