Cryopreservation of yams using vitrification modified by including droplet method: effects of cold acclimation and sucrose.

Cryopreservation of yams (Dioscorea spp.) is important for the preservation of valuable genotypes for food, medicine and breeding purposes. This study on four species of yams was conducted to evaluate the influence of cold acclimation in an alternating 5 degree C and 28 degree C, 12 h thermo-photo-period and of two sucrose concentrations in the preculture medium using a modified droplet method. Acclimation of a 3-week period provided the best preconditioning treatment averaged over four genotypes. Effect of sucrose concentration in the preculture medium depended on the genotype (significant genotype x sucrose interaction; P = 0.036). High survival (67 to 70%) with 30% to 50% shoot recovery was obtained for D. bulbifera, D. polystachya and D. cayenensis, compared to 20 percent survival without shoot recovery for D. alata.