J Appl Genetics (2011) 52:313–318 Table 1 Male fertility (mean scores) of analyzed testcrosses with the CMS-C cytoplasm Male sterile (MS) Male fertile (MF) 1-1.9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9 1) RILs heterozygous in Rfc1 locus were omitted. Total Chi2 (1:1 segregation ratio of MS:MF) P Phenotype Intervals of average male fertility scores Number of recombinant inbred lines1) 541×2020LM 541×Ot1-3 0 21 10 0 0 0 0 23 23 77 2.92 0.10-0.05 1 44 5 0 0 0 4 32 16 102 0.0004 >0.99 315 polymorphism. A similar situation was observed in the research on mapping of the Rfg1 gene controlling male fertility in rye with CMS-G cytoplasm (Börner et al. 1998). Production of fertile pollen in plants with G cytoplasm stays under control of at least three genes (Melz and Adolf 1991), but in the cross used by Börner et al. (1998) for localization of the Rfg1 locus on the 4RL chromosome, monogenic model of inheritance was assumed. It should be noted, that assessment of male fertility/ sterility of testcrosses with C cytoplasm was performed in only one environment. This does not allow us any consideration about environmental sensitivity of the studied trait. According to observations of Geiger et al. (1995) on rye plants with Pampa sterilising cytoplasm, environmental conditions are important for expression of male fertility, but their significance is rather limited to partially male fertile genotypes. This class of genotypes was not observed in testcrosses assessed in our study (Table 1), and for this reason we assumed that classification of phenotypes reported here should be sufficient for mapping purposes. The first linkage group (LOD =15) containing the Rfc1 locus was constructed after the analysis of 2281 poly- morphic markers in the 541×2020LM population. The group was composed of 174 loci (173 molecular markers and Rfc1 gene). The selection of markers very tightly linked with the Rfc1 resulted in identification of a group of 94 molecular markers (Table 2). This group consisted of three SCAR markers and 91 DArTs. Recombination frequency between Rfc1 and molecular markers, not exceeding the level of 0.01, was observed in the case of 27 DArTs. In the population 541×Ot1-3 2097 polymorphic markers were genotyped. In the linkage group containing Rfc1 locus there were 238 molecular markers (mostly DArTs), but only nine of them showed recombination frequency not exceed- ing the 0.05 level (Table 1). The mapping analysis was performed only with the use of markers revealing recombination frequency below 0.05 with the exception of Xpsr119 STS marker and the SCAR marker Xscsz23L500. Although Xscsz23L500 was localized not so close to the Rfc1 locus in the 541×Ot1-3 cross, it belonged to the group of markers tightly linked to the restorer gene in the 541×2020LM population. Seven markers (Xpsr119, Xscsz23L500, and five DArT loci) were present in both linkage maps. Considering only the order of these common markers, the genetic maps constructed for the two studied populations remain in agreement (Fig. 1). However, some significant differences between both linkage groups are easily noticed. The distances between the Xpsr119, Xscsz23L500, common DArT markers and Rfc1 gene are longer on the map of 541×Ot1-3, in spite of significantly lower number of loci in the linkage group. The same five DArT markers, which in the population 541×2020LM revealed no recombination with the Rfc1, in the cross of 541×Ot1-3 belonged to the most closely located markers, but with the distance of about 5 cM. Table 2 Number of markers within the linkage groups and their recombination frequency with the Rfc1 locus Recombination frequency 541×2020LM 541×Ot1-3 <0.01 0.01-0.02 0.02-0.03 0.03-0.04 0.04-0.05 Total in the linkage group1) 27 9 42 7 9 173 1) linkage groups containing the Rfc1 locus were constructed at LOD= 15. 0 0 0 0 9 238