QTLs associated with powdery mildew resistance responses in roses

In roses, powdery mildew is one of the most important fungal pathogens. Host plant resistance exists in roses for example by highly localized host responses. Nevertheless, breeding for better resistant roses is difficult because of the occurrence of powdery mildew pathotypes. Also, in the development of molecular markers, pathotypes and plant specificity are very important. We used two ways of evaluating the pathogen-plant interaction to develop QTLs for two powdery mildew pathotypes. An existing genetic map developed for a rose hybrid F1-population (n=90) was used for disease resistance response and QTL development. The parent plants used, ‘Yesterday’ and Rosa wichurana, exhibit different resistance responses towards the two rose powdery mildew pathotypes, R-E and R-P. Existing data and QTLs on the rose-powdery mildew interaction evaluated by scoring fungal development were compared to additional data and QTLs on cell responses in the rose leaves.