Biotechnology of tamarillo (Cyphomandra betacea): From in vitro cloning to genetic transformation

Cyphomandra betacea (Solanaceae), commonly known as tamarillo, produces edible fruits with a high content of vitamins, minerals, phenolic and carotenoid compounds. The species is originated from Andean regions of South America but is cultivated in different regions of the world, mainly in Colombia, USA and New Zealand, which is now the main producer and exporter of this still underutilised crop. Tamarillo can be propagated by conventional methods such as seeds and cuttings but problems such as poor rooting ability and variability of the obtained plants have restricted their application. In vitro propagation and genetic transformation are valuable biotechnology tools that can be applied to tamarillo breeding. Protocols for the in vitro regeneration of tamarillo have been established, including axillary shoot proliferation, induction of organogenesis and somatic embryogenesis. Somatic embryogenesis is particularly interesting whether it could be applied to the propagation of adult selected trees. The data now available have shown that somatic embryogenesis can be easily induced from juvenile explants such as zygotic embryos, hypocotyls and young leaves but direct regeneration from adult explants was not yet achieved. However, leaves of in vitro established adult plants can be used to induce somatic embryogenesis, an indirect approach to achieve the propagation of particular trees. Protocols for genetic transformation of tamarillo have been developed and can be applied, in the future, to the regeneration of plants with suitable characteristics. Genetic transformation is also being used as a functional genomics tool, helping to better understand the process of somatic embryogenesis. In this article the information available concerning the biotechnology of this important horticultural tree is reviewed and updated.

► Tamarillo is an important fruit crop with interesting nutritional properties.
► In vitro propagation and genetic transformation can be applied to tamarillo breeding.
► Embryogenic and non-embryogenic tissues can be obtained from the same explant.
► Cloning of adult trees through somatic embryogenesis was achieved.
► Genetic transformation protocols are being used to better understand the embryogenic process.