316 J Appl Genetics (2011) 52:313–318 Fig. 1 Linkage groups of molecular markers from 4RL chromosome and localization of Rfc1 gene. Positions of loci common for both mapping populations are printed in bold. Markers located in the same position on the genetic map are framed The results of this study enable more precise localization of Rfc1 locus than the interval mapping analyses performed before (Stojałowski et al. 2004; Hackauf et al. 2009). In the mapping population (544cms-C×Ot0-20 intercross) used during these former studies, activity of at least two restorer genes was observed resulting in problems with precise localization of the Rfc1 locus on the 4RL chromosome. Linkage maps developed with the use of reported here mapping populations allowed for more accurate localization of this restorer gene. On the other hand, some inconsisten- cies occurred when both new genetic maps were compared. First of all, at the moment it is difficult to explain the unexpected differences in the results of selection of the most tightly linked markers in both related mapping populations. The source of non-restorer alleles was the same in both crosses. Naturally, it can not be absolutely excluded that the restorer locus in lines 2020LM and Ot1-3 is different, but the presence of the same markers revealing lower recombination frequency and similar order of loci on both genetic maps indicates that it is rather the same gene. The total number of polymorphic molecular markers was comparable in both crosses, as well as the number of loci within the identified linkage groups containing the Rfc1 locus. It seems, however, that the level of recombination events on the long arm of 4R chromosome was slightly higher in the population 541×Ot1-3. Distances between loci Table 3 Distances between Rfc1 gene and molecular markers loci on the integrated genetic map of the 4RL chromosome and estimated frequencies of recombinants Marker Distance to the Rfc1 (cM) Frequency of recombinants between a marker and Rfc1 locus per one generation (%) Xpsr119 Xscsz23L500 XrPt508318 XrPt389935 XrPt508766 XrPt398602 XrPt505810 25.04 5.06 2.52 2.51 2.50 2.49 2.47 Mean 6.05 1.37 0.65 0.63 0.63 0.61 0.57 Standard deviation 1.09 0.70 0.75 0.73 0.73 0.71 0.66