Cross Breeding And Cross-compatibility Between Rosa Rugosa And Modern Roses

Rosa cvs, which are famous for their gorgeous colors, graceful flower shapes, abundant cultivars and varied types, have become one of the most widely used ornamental plants. At present, there are more than25,000Rosa cultivars, which have a quite limited genetic background as they were developed by crossing and back crossing with merely7-15wild species. As a result, the fragrance of modern roses faded away and the disease resistance declined gradually. It is an important way to breed new rose cultivars with fragrance and strong resistance by introducing prominent genes of agreeable scent and strong resistance to disease and adversity into its simplex genome background via inter-specific crossing.Rosa rugosa, a well-known Chinese traditional flower, has many prominent traits, including strong hardiness, excellent resistance to drought and disease, remarkable saline-alkaline tolerance, and intense perfume, which make it a valuable parent material in breeding of new rose cultivars. In this study, R. rugosa cultivars and modern rose cultivars were used as parents to breed new rose cultivars with fragrance and strong resistance to disease. And the influence of ploidy level and karyotype of parents on inter-specific cross compability was discussed. The main results were as follows:1.11.R. rugosa cultivars and56modern rose cultivars were used as parents in77crossing combinations, among which13compatible crossing combinations were selected and143F1plants were obtained. The fruit setting rate of inter-specific crossings were obviously higher in combinations with modern rose cultivars, whose self-crossing fruit setting rate were higher, as female parents.2. Thorns and leaflet numbers of hybrid plants obtained showed an obvious similarity to male parents (R. rugosa cultivars), while the leaf surface was more like female parents (modern rose cultivars). The flower colors, types, sizes and the petal texture of hybrid plants showed a separation between the male and female parents.SSR molecular markers were used in hybrid identification of10F1plants, and all the10plants were confirmed as real hybrids. In addition, Flow cytometry was used to identify the ploidy levels of6hybrids, and all of which were confirmed as triploids. The results also showed that the6tested hybrids were true progeny of modern roses (4x) and R. rugosa (2x). 3. Traditional squashing method was used in karyotype analysis of7modern rose cultivars and5R. rugosa cultivars, to explore the influence of ploidy level and karyotype on inter-specific cross compability, and it was found that the karyotypes of cross-compatible parents were similar, which indicated that the difference of evolution level between female and male parents could have some relationship with inter-specific compatibility. The results in this study laid foundation for efficient breeding new cultivars with intense fragrance and strong resistance, using R. rugosa as parent.