Sapogenin production in relation to age of tuber in two Dioscorea species

Abstract

Two sexually propagated, sapogenin-producing Dioscorea selections were tested over 54 months of growth to determine the rate of steroid deposition and production. In both selections, sapogenin concentration increased with tuber age. In Dioscorea floribunda, sapogenin concentration increased more rapidly than in D. composita, but because of rapid tuber growth, D. composita surpassed the other species in total sapogenin yield after the third growth season. Decreases in sapogenin content were noted during spring growth and increases in summer and fall. D. floribunda can be harvested after three growing seasons, while four or five growing seasons can increase the average annual yield of D. composita. Both species should be harvested during winter when sapogenin content is more stable.