Effects of oligosaccharide elicitors from endophyitc Fusarium oxysporum Dzf17 on diosgenin accumulation in Dioscorea zingiberensis seedling cultures

The effects of the oligosaccharides prepared from endophytic fungus Fusarium oxysporumDzf17 on diosgenin accumulation in Dioscorea zingiberensis seedling cultures were investigated. Among three oligosaccharide fractions (DP2-5, DP5-8, and DP8-12), DP8-12 at concentration of 20 mg/L resulted in the highest diosgenin content and yield of the seedlings with the values individually as 1.28 mg/g dw and 18.05 mg/L, which were 4.76-and 5.65-fold higher, respectively compared to the control. Among three oligosaccharide monomers (DP4, DP7, and DP10) separately derived from fractions DP2-5, DP5-8, and DP8-12, DP10 showed the most significant enhancement on diosgenin accumulation. When the seedlings were treated with DP10 at 6 mg/L and harvested on day 36 of culture, both diosgenin content and yield increased to 1.85 mg/g dw and 27.69 mg/L, which were 7.24-and 9.33-fold higher respectively compared to the control. The results indicated that addition of the oligosaccharides from endophytic fungus F. oxysporum Dzf17 as elicitors could significantly enhance diosgenin production in D. zingiberensis seedling cultures.   Key words: Dioscorea zingiberensis, endophytic fungus, Fusarium oxysporum Dzf17, seedlings, polysaccharide, oligosaccharide, diosgenin.