Seed set by artificial pollination and seed storage under cryogenic, freezer and dry conditions in the medicinal plant Uncaria rhynchophylla

Abstract

Uncaria rhynchophylla (Rubiaceae), a woody liana with significant medicinal value, has been used as a traditional Japanese and Chinese medicine. While effective seed production is required for breeding and efficient seedling production, the physiology of sexual reproduction remains largely unknown in this species. Therefore, we first observed the flowering behaviour, and next attempted artificial pollination using flowering individuals in a greenhouse. In this study it became clear that this species sets seeds by allogamy, but not by autogamy. The obtained seeds showed about a 90% germination rate. We also examined seed desiccation tolerance and storage conditions which are important to preserve the genetic resources. Seeds of this species were found to have a characteristic of the orthodox type, having high desiccation tolerance. Seeds after 6 months of storage at + 22, −20 and −160°C showed comparable germination rates to the seeds before storage.