Induction and Identification of Colchicine-mediated Polyploidy in Three Rosa roxburghii Accessions

The induction of polyploidy in Rosa roxburghii has significant potential to enhance the horticultural and commercial value of this crop and meet specific market demands. In this study, seeds from three R. roxburghii germplasms were germinated and then treated with colchicine to induce polyploidy. The polyploids were identified using morphology, physiology, and cytology, and this study predicts prickleless traits in the polyploids through marker-assisted selection. The results indicate that the highest induction rate was reached after 12 hours of treatment with 1% colchicine. In total, 20 new mutants were successfully obtained, comprising two mutants from Wuci1 seed, three mutants from Wuci2 seed, and 15 mutants from Duanci1 seed. Aspects of morphology and physiology varied significantly between diploids and polyploids. The leaflet width and leaflet shape index of polyploid seedlings from three R. roxburghii germplasms showed a substantial increase, and the relative chlorophyll content was significantly higher than in diploid seedlings. Furthermore, there were differences in stomatal length, guard cell length, and stomatal density. Additionally, the main vein diameter, upper epidermal thickness, palisade tissue, and sponge tissue of polyploid leaves were greater than in those of diploid leaves. Furthermore, using insertion-deletion (InDel)-specific molecular markers, polymerase chain reaction (PCR) amplification was performed on 15 polyploids from Duanci1 seeds and predicted that three polyploids may carry the prickleless fruit trait. These polyploid mutants provide valuable materials for breeding large-fruited types of R. roxburghii without prickles and lay a theoretical foundation for future research.