No abstract

Yacon (Smallanthus sonchifolius) is a tuberous root crop native to the Andean region. The eatable tubers contain up to 70% fructooligosaccharides (FOS) on a dry matter (DM) basis. These FOS are not digestible by the human intestinal tract and do not cause an increase of blood glucose level. Therefore, the consumption of yacon tubers offers health promoting benefits. With regard to cultivation, little to no information about yield potential and FOS content as well as sugar composition of diverse genotypes is known. However, this information is crucial for the development of new health beneficial food products out of different genotypes of yacon. In the present study nine different genotypes were studied in a field experiment in 2017 and 2018 regarding their tuber yield formation, sugar yield, and sugar composition. The genotypes red-shelled (‘RG’), brown-shelled (‘BG’), and ‘Morado’ reached the highest tuber yields of 46.6, 43.5, and 41.6 t ha−1 FM, respectively. These three genotypes also had the highest sugar yields in the same order (2.2, 2.0, and 1.9 t ha−1). Considering the sugar composition and sugar content, these three genotypes were outstanding, with a sugar content up to 66% of DM (‘RG’, 2018). With regards to the development of possible food products, cv. ‘Peru’ can be considered as favorable for the fresh market due to high amounts of both monosaccharides and FOS. Genotypes ‘BG’, ‘RG’, and ‘Morado’ seem to offer various options for the food processing industry, due to their high amounts of FOS.

As the prevalence of diabetes is predicted to rise globally in the coming decades, the demand for sugar substitutes is expected to increase significantly. In this context, natural sweeteners have been receiving particular attention, as artificial sweeteners have been associated with obesity and cardiovascular disease. One natural sweetener is yacon (Smallanthus sonchifolius) ((Poepp. and Endl.) H. Robinson), which could play a prominent role due to its high fructooligosaccharides yield. Yacon is currently only a minor crop in Europe and there is little information available on the environmental and economic impacts of its various cultivation systems. These are especially affected by nitrogen fertilization levels and genotype selection. Thus, before the crop is introduced on a larger scale, it is expedient to identify the most sustainable cultivation system. The life-cycle assessment (LCA) and life-cycle costing (LCC) analysis of yacon cultivation systems conducted in this study revealed significant differences between yacon genotypes and found that a nitrogen fertilization level of 80 kg N ha−1 significantly decreased production costs and simultaneously led to a comparatively good environmental performance. The results indicated that, for the holistic evaluation of agricultural systems, it is crucial to assess both the economic and environmental performance of new crops.

The tuberous root crop, yacon, is native to the Andean region and contains high amountsof fructooligosaccharides (FOS) with up to 70% of dry matter. Due to FOS, consumption of tubersmay have health-promoting effects. However, regarding the overall cultivation system, norecommendations exist for farmers on nitrogen fertilization and nitrogen (N) uptake of yacon.Therefore, three different N fertilization levels (0, 40, and 80 kg N ha−1) and two genotypes (brownshelled(BG) and red-shelled (RG)) were examined in a two-year field experiment regarding theirtuber yield, sugar composition, and nitrogen uptake. Tuber yields increased with increasingfertilization level and were highest for B80 and R80 (50 and 67 t FM ha−1), while significantdifferences between the genotypes existed. Sugar and the amount of FOS slightly decreased withincreasing N fertilization level, and ranged between 36% and 73% and 30% and 58% of dry matter,respectively. An overall decreasing amount of FOS led to a slight increase in the amount of FOSwith a higher degree of polymerization. Regarding the N-use efficiency of tubers and the total plant,an N fertilization level of 40 kg N ha−1 seems to favor tuber yield.