Main research question/goal
Breeding for disease resistance is a priority in garden roses. This research focuses on breeding for better resistance towards powdery mildew (Podosphaera pannosa) by specific selection procedures, increasing knowledge of the disease and plant resistance. Powdery mildew is one of the main rose diseases. The disease occurs in greenhouses on cut roses as wall as on field grown garden roses.Research approach
We focus on the combination of characteristics of the pathogen and resistance in the plant: differences in virulence between pathotypes, resistance reactions in leaves during fungal development and molecular markers for disease resistance.
Differences in resistance are studied in a diploid rose population (‘Yesterday’ x R. wichurana). For the offspring plants, differences in resistance are found for powdery mildew pathotypes. A genetic map for roses is also developed. This map serves for the location of molecular markers (QTLs – Quantitative Trait Loci) for pathotype specific resistance. Relevance/Valorisation
In this study it was shown that different resistance reactions occur in roses. In the rose cultivar ‘Yesterday’ for one specific pathotype of powdery mildew, conidia germinate but further development is stopped. In another pathotype the fungus develops but cellular reactions are part of the plant defense. Certain cells die when the fungus tries to get established (hypersensitivity response). Numbers of cells responding leads to diminished fungal growth. Pathothype specific QTLs are found on the genetic map of roses. It is possible to combine defence responses by hybridization of specific rose genotypes; this results in a rose with improved resistance.