A First Step in Short-Term Conserving Nuclear-Stock Plum via Seed Encapsulation

Shoot tips from ten Prunus domestica L. cultivars, maintained as pathogen-free pre-basic material and preserved ex situ under insect-proof conditions, were encapsulated in calcium alginate, to evaluate their short-term conservation potential. The germination and regrowth capacity of encapsulated explants, developed under different carbon sources, storage conditions and dehydration treatments were assessed. Two experimental approaches were performed: (i) shoot tips encapsulated in MS medium supplemented with 3% sucrose, sorbitol, or mannitol, stored at 4 °C in darkness for 90 days; (ii) shoot tips encapsulated in MS medium supplemented with 3% sucrose, with or without prior dehydration in sucrose solution, and stored either at 22 °C or 4 °C under 16/8 h photoperiod for eight weeks. All cultivars exhibited vigorous shoot formation in vitro, and the encapsulated shoot tips showed a good regrowth capacity for storage. Sucrose encapsulated explants regenerated successfully after 60 days in the first experiment, with rates of 50% for ‘Geta’ and 36.7% for ‘Gras Ameliorat’. In the second one, the highest regrowth rate was observed at 4 °C after six weeks for ‘Geta’ (67.8%), and after eight weeks under sucrose-induce dehydration for ‘Gras Ameliorat’ (67.8%). These results demonstrate that synthetic seed technology, when combined with optimized storage conditions can effectively support the short-term conservation of the tested plum cultivars.