Droplet-vitrification methods for apical bud cryopreservation of yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Rob.]

This study aimed to develop a cryopreservation protocol for the long-term preservation of yacon [ Smallanthus sonchifolius (Poepp. and Endl.)], an Andean crop with high fructooligosaccharide content in its tuberous roots. Initially, the cryopreservation protocol was developed using a yacon clone originated from Ecuador classified as ECU 41. Osmotic dehydration of apical buds (2–3 mm long) was carried out by assessing two plant vitrification solutions, PVS2 (15, 30, and 60 min) at 0 °C and PVS3 (30, 45, 60, and 75 min) at 22 °C. After cryopreservation, the apical buds were thawed and placed on MS medium ± 0.1 mg l −1 N 6 -benzyladenine (BA). The survival rates ranged from 37 to 90% within all treatments, with those subjected to PVS2 and PVS3 for 60 min showing the highest survival rates on MS medium without BA (87 and 90%, respectively). At 12 weeks post cryopreservation, these treatments also provided the highest regrowth rates, both reaching 73% of normally growing (shooting, rooting) plantlets. Survival rates on MS + 0.1 mg l −1 BA regrowth medium reached up to 90%; however, regrowth into normally rooted plantlets did not exceed 67% post cryopreservation. The optimized protocols were then applied to 4 additional yacon clones originated from Bolivia and Peru, classified as BOL 22, BOL 23, PER 12, and PER 14. This resulted in survival and regeneration rates ranging between 79.7–94.1% and 66.3–75.4% respectively. Our study shows that optimal cryopreservation protocols for the long-term conservation of yacon can be based on both PVS2 and PVS3 vitrification solutions. Key message An efficient PVS2 and PVS3 based cryopreservation protocol for yacon was developed, ensuring shoot tip survival of up to 94.1% and subsequent regrowth up to 75.4% after cryopreservation.