In peach [Prunus persica (L.) Batsch], trees showing columnar (also termed pillar or broomy) growth habit are of interest for high-density production systems. While the selection of the pillar homozygous phenotype (brbr) can be carried out prior to field planting, the intermediate heterozygous upright phenotype is difficult to distinguish from standard trees until they are quite large in the field. Application of marker-assisted selection would be helpful in establishing more efficient breeding programmes developing pillar and upright varieties. Thirty-four amplified fragment length polymorphism (AFLP) markers and three simple sequence repeat (SSR) markers identified by bulked segregant analyses mapped together with the br gene on linkage group 2 (LG 2) of the Prunus reference map. The linkage group covers 92.9 cM. The AFLP marker ETGM61_291R mapped with 4.8 cM to the br gene on one side and the closest AFLP markers ETAM56_267A, ECAM61_426A and ETAM48_279A with 3.8 cM on the other side. These four AFLP markers were sequenced, and two, ETGM61_291R and ETAM48_279A, were successfully converted into sequence-tagged site (STS) markers for marker-assisted selection. BLAST searches against the peach genome placed the br gene in the region 17-18 Mb on LG 2.
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.
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