W481 Genetic Complexity of Black Spot Resistance in Roses

Date: Saturday, January 14, 2012
Time: 8:00 AM
Room: Royal Palm Salon 1-2
Thomas Debener , Leibniz University Hannover, Niedesachsen, Germany
Diro Terefe-Ayana , Leibniz Universtitšt Hannover, Hannover, Germany
Marcus Linde , Leibniz University of Hannover, Lower Saxony, Germany
Meraluna Canunayon , Leibniz Universtitšt Hannover, Hannover, Germany
Dennis Burgwinkel , Leibniz University of Hannover, Hannover, Germany
Black spot is the most devastating disease of field grown roses. Previously we have characterized single dominant black spot disease resistance genes in diploid hybrids and cloned one of these genes which is a member of a TIR-NBS-LRR (TNL) gene family with nine members in a resistant Rosa multiflora genotype. We compared different rose genotypes for the genetic diversity at the locus using SSR-markers generated from the LRR region of the gene and indicated distinct patterns for all TNLs. Furthermore we sequenced an additional contig from a second rose species, Rosa rugosa, with 11 copies and compared the structure of the locus in roses to the syntenic regions of the strawberry, peach, apple, Medicago and Arabidopsis genome. Preliminary analyses indicate that the black spot resistance (Rdr1) locus is a young locus with possible duplication after the divergence of the Rosoideae from other Rosaceae. Unlike short-living annual plants, the rose TNLs are highly similar and clustered within close proximity. Nevertheless, extensive sequence rearrangements based on unequal crossing over, gene conversion and mutations occurred within the rose gene family are similar to observations made in annuals. Evolutionary rates of theTNL clusters is much higher as compared to those of other genes at the locus if rosaceous and non rosaceous species are compared. Recent results from a third species (Rosa majalis) with resistance to black spot show that three additional resistance genes map within the cluster of Rdr1 homologues.