Is Breeding the Answer? How Long Will It Take?

Rose Rosette Disease is caused by the Rose Rosette Virus (RRV) and transmitted by a wind-blown eriophyid mite (Phyllocoptes fructiphilus). Little is known about the resistance of the rose to the virus or the mite vector. At present only a few species such as Rosa palustris, Rosa setigera, Rosa carolina, Rosa virginiana, and Rosa spinosissima but no cultivated roses have been reported resistant to the disease. Preliminary observational data indicates that there is resistance to the disease among the cultivated rose germplasm. Experiments in Tennessee and Delaware are in place to verify which cultivars are resistant. Although work is being done with the resistant species, the introgression process of transferring the resistance from a cultivated rose to develop new resistant rose types would be quicker than starting with resistance from a species rose. In both situations, breeding tools such as marker-RRD resistance associations are being explored. The protocol to generate molecular markers via genotyping by sequencing has been developed for roses and a consensus map with more than 1,000 markers has been constructed. Crosses have been made among various RRD resistant rose species and putatively resistant commercial roses on both the diploid and tetraploid level. These populations will allow an accurate assessment of the inheritance of and the identification of markers associated with RRD resistance to accelerate its introgression into a range of rose germplasm.