In vitro sucrose concentration influences microtuber production and diosgenin content in white yam (Dioscorea rotundata Poir)

Abstract

Dioscorea spp. is an important food crop in many countries and the source of the phytochemical diosgenin. Efficient microtuber production could provide source materials for farm-planting stock, for food markets, and for the production of high-diosgenin-producing cultivars. The first step in this study was optimizing the plant growth regulators for plantlet production, followed by a study of the effects of sucrose concentration on microtuber induction and diosgenin production. Significantly, more shoots (3.5) were produced at 4.65 μM (1 mg L−1) kinetin (KIN), longer shoots (4.1 cm) were obtained at 2.46 μM (0.5 mg L−1) indole-3-butyric acid (IBA), and root number (3.9) was significantly higher at 5.38 μM (1 mg L−1) naphthalene acetic acid (NAA) than in other treatments. Increased sucrose concentrations in the optimized growth medium with 4.65 μM KIN and 5.38 μM NAA had significant effects on microtuber production (p < 0.01) and diosgenin content (p < 0.05). The most microtubers (6.2) were obtained with 100 g L−1 sucrose, while those on 80 g L−1 sucrose were the heaviest (0.7 g) and longest (7.4 mm). Microtubers formed in medium with 80 g L−1 sucrose had significantly higher diosgenin content (3.64% [w/w]) than those in other sucrose treatments (< 2%) and was similar to that of field-grown parent tubers (3.79%). This result indicates an important role for sucrose in both microtuber growth and diosgenin production. Medium containing 4.65 μM KIN and 5.38 μM NAA is recommended for plantlet production, and medium containing 80 g L−1 sucrose is recommended for microtuber and diosgenin production.