An SSR from the leucine‐rich repeat region of the rose Rdr1 gene family is a useful resistance gene analogue marker for roses and other Rosaceae

P>We developed the Rd1LRR microsatellite marker from a highly conserved part of the LRR region of nine completely sequenced Rdr1 paralogues of a black spot-resistant Rosa multiflora genotype. The black spot resistance gene Rdr1 belongs to the class of nucleotide-binding site and leucine-rich repeat (NBS-LRR)-encoding genes. The occurrence of a distinct (CT)(n) repeat in each Rdr1 paralogue allowed us to fingerprint rose genotypes for the diversity within the Rdr1 gene family. PCR analysis with Rd1LRR in 34 rose cultivars resulted in 52 distinct bands corresponding to a minimum of 52 different NBS-LRR encoding resistance gene analogue genes. In addition, 31 wild rose species and 34 accessions of R. arvensis were analysed with this marker. The high diversity for the number and allelic composition of Rd1LRR banding patterns even within individuals of R. arvensis indicated that the Rdr1 locus is highly diverse. The Rd1LRR may be used in future mapping projects for tests of cosegregation of new resistance specificities to the Rdr1 gene cluster. Furthermore, this marker is a useful tool for the identification of distinct Rdr1 genes in cloning experiments.