Teruo Tsukihashi

Composition of storage carbohydrate in tubers of yacon (Polymnia sonchifolia)

Abstract Yacon (Polymnia sonchifolia or P. edulis; Compositae or Asteraceae) plants originating from the Andean highlands have large (100-500 g FW) subterranean tubers, and the fresh, boiled or fried tubers are edible. The appearance of the yacon tubers is similar to that of the dahlia or sweet potato tubers, but the fresh yacon tubers are juicy and sweet like fruits such as pears. Recently, yacon cultivation has been introduced to Japan.

Studies on the Cultivation of Yacon(Polymnia sonchifolia) (VIII) Effect of topdressing on the growth and yield of yacon.

Tuberous roots of yacon (Polymnia sonchifolia) contain a large amount of oligofructans. So, they draw great attention as a healthful diet. Powder of tuberous roots and tea of leaves are commercially sold.Establishment of yacon cultivation technique is now a necessity. But the effect of topdressing on growth and yield of yacon has not yet been tested.Effects of topdressing were tested in 1993 and 1994.Results as follows:1) Tops of yacon grew vigorously and stem numbers increased by topdressing.2) Total yield of tuberous roots did not increase by topdressing.3) Yield of tuberous roots exceeding 300-400g decreased by topdressing.4) Topdressing has little effect on yield of tuberous roots in the tested.

Studies on the Cultivation of Yacon(Polymnia sonchifolia). (VI) Influence of the methods of ridging on the growth and yield of yacon.

We have been cultivation tests of Yacon (Polymnia sonchiforia) since 1987, and their results were reported. But it is not yet tested that the influence of ridging on the growth and yield of yacon.We tested on the influence of the methods of ridging on the growth and yield of yacon in Light-colored Andosol.Three experimental plots were made; level row plot, level row→high ridge (by earthing up) plot and high ridge plot. Three replications were made on each plot.The results were as follows:1) Growth of yacon of main stem in all stage was nonsignificant difference in each plot.2) The top was produced 748g/plant in level row plot, 900g/plant in level row→high ridge plot and 904g/plant in high ridge plot, but nonsignificant difference in each plot.3) The tuberous roots was produced 1268g/plant in level row plot, 1280g/plant in level row→high ridge plot and 1584g/plant in high ridge plot, but nonsignificant difference in each plot.4) From yield of yacon tuberous roots in each plot, it was suggestted that the earthing up at August 4, it would have little influence on yacon yield.5) From yield of yacon tuberous roots in each plot, it was judged that high ridge culture would be useful for the harvest of the tuberous roots of yacon with a potato digger.