The utilisation of molecular tools for rose breeding and genetics

Roses are among the most important ornamental plants worldwide. Despite its economic importance, little work has yet been conducted to elucidate the inheritance of important characters. An overview of the molecular tools currently applied to rose research and breeding is given and examples from our own research programs are presented. We have begun to analyse morphological characters and resistance to two of the most important pathogens, blackspot and powdery mildew, both genetically and molecularly. Several morphological traits including single genes and Qtls (quantitative trait loci) were mapped relative to molecular markers. For resistance to black spot and powdery mildew, one resistance gene each were mapped on the rose chromosome map. In addition, for Rdr1, a gene conferring resistance to black spot, high density mapping and the isolation of BAC-clones with closely linked markers led to the identification of a contig carrying several disease resistance analogous sequences which spanned the locus. The structure of this locus and the identification of Rdr1 among the candidate genes are currently under investigation. Furthermore, strategies for the marker assisted selection against the genetic background of wild donor species in introgression programs were developed. Within two generations of backcrossing, wild donor germplasm could be reduced more effectively by means of molecular markers than by conventional morphological analyses. In addition to the application of molecular markers, a regeneration and transformation protocol for roses has been established and.