The Application of Biotechnology in an Integrated Project of Conservation and Utilization of Papaya and Its Wild Relatives
Carica papaya is an important crop species throughout tropical and subtropical regions of the world, including northern regions of Australia. Biotechnology is relatively advanced in papaya including techniques for micropropagation, embryogenesis, embryo rescue, transformation and the application of molecular markers. Plant improvement projects are underpinned by such technologies but also require a range of germplasm as a source of new and useful agronomic traits. A collection of valuable germplasm in the form of superior cropping genotypes of papaya and wild relatives of papaya, the Vasconcella spp., are being used in a range of plant improvement projects in our laboratories. The Vasconcella spp. are a particularly rich source of agronomically important traits, including resistance to papaya ringspot virus type P (PRSV-P), phytophthora, phytoplasma and blackspot. Intergeneric hybrids between wild relatives and papaya are now segregating for PVSP-P and molecular mapping and marker technologies are assisting with further selection of useful hybrid plants. The long-term conservation and availability of this range of germplasm is critical to sustainable utilization. Tropical fruits are typically difficult to store as seed and we are currently involved in international collaborations to develop alternative conservation technologies for tropical fruits, including papaya. This paper reports on advances in seed storage technologies, slow-growth storage and cryopreservation of both shoot tips and seeds as alternatives for use across a range of papaya genotypes for long-term ex situ conservation.