Cryopreservation of Bletilla striata mature seeds, 3-day germinating seeds and protocorms by droplet-vitrification

Abstract

Droplet-vitrification was studied for the cryopreservation of Bletilla striata mature seeds (0 day after sowing), 3-day germinating seeds and protocorms (6, 9 and 12 days after sowing). Mature seeds, 3-day germinating seeds and 6-day old protocorms were precultured in liquid medium supplemented with 0.3 M sucrose for 3 hon a shaker (110 rpm) and then dehydrated with 2 M glycerol and 0.4 M sucrose in liquid medium (loading solution) for 15 min and exposed to PVS2 solution for 60 min at 25°C. The plant materials were then immersed in liquid nitrogen, rewarmed rapidly and cultured on solidified ND medium supplemented with 3% sucrose for recovery. After cryopreservation, the highest germination percentage of mature seeds, 3-day germinating seeds and survival of cryopreserved 6-day old protocorms was 93%, 91% and 84%, respectively. For 9-day old protocorms, highest survival (66%) after cryopreservation was achieved after preculture with 0.5 M sucrose for 3 h on a shaker, dehydration with loading solution for 15 min, exposure to PVS2 solution for 40 min at 25°C, and culture on solidified ND medium supplemented with 480 mg l-1ammonium nitrate and 3% sucrose. No survival was observed in cryopreserved 12-day old protocorms. © CryoLetters, c/o University of Bedfordshire.