Dormancy release, germination and ex situ conservation of the southern highland papaya (Vasconcellea quercifolia, Caricaceae), a wild crop relative

The genetic traits of wild species closely related to crop plants provide opportunities for increased crop production and food security in the face of global climate change. Highland papayas, Vasconcellea spp., have valuable traits for the improvement of common papaya. Vasconcellea quercifolia is the only species of the genus that inhabits both the Andean lowlands and highlands, and it has been proposed as the best option for intergenic hybrids. However, limited information is available on seed dormancy release, germination and ex situ conservation of species belonging to this genus. We investigated the effects of desiccation and storage, in combination with seven pre-germination treatments, on dormancy release and viability of seeds from five wild populations of V. quercifolia along a latitudinal gradient in NW Argentina. Effectiveness of pre-germination treatments on dormancy release increased concomitantly with a decrease in seed moisture content (MC). Ultra-dry (<3 % MC) in combination with potassium nitrate treatment, as well as dry (3-5 % MC) storage at 25 degrees C consistently alleviated seed dormancy. In general, desiccation and dry storage for 6 months at different temperatures did not affect seed viability; however, there were population differences in the ability of seeds to remain viable. Our data demonstrate the central role of seed MC in the alleviation of V. quercifolia seed dormancy and provide new insights into the conditions required for short- to medium-term ex situ conservation.