Evaluation of Rosa palustris As a Parent for Breeding Rose Rosette Disease-resistant Roses

Rose rosette disease (RRD) is a viral disease of the genus Rosa, causing plant death in 2-4 years. No cultivars have been confirmed to be resistant and no consistently effective control methods exist, making the breeding of resistant rose cultivars a priority. To this end, we investigated the usefulness of Rosa palustris Marsh., a species reported resistant to RRD though seldom used in rose breeding, as a parent in breeding for RRD resistance. Rosa palustris was crossed with various cultivars chosen either for their reported resistance to RRD or for their past success as breeding parents. Additionally, crosses were made between these cultivars for a total of 90 unique crosses. Success of crosses was determined by hip set, seed production and germination rates. Rosa palustris was most successful as a parent when used as a male; however, most crosses with R. palustris still resulted in high flower abortion. Embryo rescue was performed on select R. palustris crosses but with limited success. We suggest this is due to the wide nature of these crosses, as R. palustris is in section Carolinae while most cultivars are hybrids from sections Synstylae and Indicae. While attempts to breed with R. palustris will be continued, future breeding will focus on alternative parents, such as reported-resistant Rosa setigera (section Synstylae), which may prove more productive.