Yacon

1. Yacon (Smallanthus sonchifolius) Classification

Superkingdom: Eukaryotes

Kingdom: Plantae (Plants)

Subkingdom: Tracheobionta (Vascular plants)

Superdivision: Spermatophyta (Seed plants)

Division: Magnoliophyta (Flowering plants)

Class: Magnoliopsida (Dicotyledons)

Subclass: Asteridae

Order: Asterales

Family: Compositae = Asteraceae (Aster Family)

Tribe: Heliantheae

Subtribe: Melampodinae

Genus: Smallanthus Mackenzie

Species: Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson; in Phytologia 39: 51. 1978.

Common Names: “leafcup”, “yacón”, “yacon strawberry” Castilian/Spanish: Peru, Bolivia, Argentina “yacón”, “llacon”, “llacjon”, “llag'on”; Colombia “arboloco”; Colombia, Venezuela “jíquima”, “jiquimilla”. Aymara: Peru, Bolivia “aricoma”. French: “poire de terre”.

Colloquially, Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson has also been named “apple of the earth”, because of the fact that its root is eaten raw and possesses a sweet tasting and crunchy texture. The term yacón and its derivatives come from Quechuan words; yacu and unu are words that mean «water», whereas yakku is an adjective that means «watery» or «insipid», alluding to its tuberous roots, which are watery and insipid immediately after harvest. The terms jícama, jíquima, jiquimilla, jikima and derivatives are the result of the similarity between its roots and those from Pachyrrhizus sp., “jícama”.

The term yacón is also applied in Argentina and Paraguay to the species Jacaratia hassleriana Chod., a Caricaceae with juicy roots weighting up to 60 kg, and used as source of water in the dry forest where it grows.

Synonyms:

• Polymnia sonchifolia Poeppig & Endlicher, Nov. Gen. Sp. Pl. 3: 47. 1845.
• Polymnia edulis Weddell Ann. Sci. Nat. Bot. IV. 7: 114. 1857 (Typus, P).

Related Species:

Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson belongs to the same family of sunflower, common daisy, dandelion, and lettuce, among other species. Its closest relatives are, evidently, species within the genus Smallanthus. In total, 21 species for this genus are known; all of them are endemic to America. Most of these 21 species are restricted to regions of temperate climate. Near the equator, some species proliferate at altitudes over 3 000 m asl, whereas others grow up almost at sea level. No one of them –except Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson—produces tubers.

There exist 3 species within the same genus that are used as medicinal. These species are Smallanthus uvedalius (L.) Mackenzie (Uphof, 1968), Smallanthus glabratus (DC) H. Robinson (Wells, 1965:156) and Smallanthus maculatus (Cav.) H. Robinson (Lipp 1971). In Peru, there also exists a Smallanthus species, 5 m in height that is locally known as taraca or yarita, whose stems are used to make thatches (Weberbauer, 1945:198).

Within its own family, the family Compositae or Asteraceae, Smallanthus sonchifolius shares the property of stocking carbohydrates in the form of inulin –or inulin-related compounds—with most of the species. However, inulin or inulin-related molecules seldom appear in such concentration or such purity as they do in Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson. There exist only few species with a considerable content of inulin.

One of this few species is Helianthus tuberosus, “Jerusalem artichoke” or “topinambur”, native to North America, that also produces underground tuberous roots. However, these tuberous roots are amorphous and extremely knotty, so that cleaning them is a hard task. The tuberous roots have to be brushed and polished under a water jet in order to remove the earth and dirt deposited within its knots and curves, although they do not need to be peeled. There exists a French cultivar of Helianthus tuberosus called ‘Fusau’ that has less knots, but many people say this cultivar is not as delicious as knotty cultivars. All these facts turn commercial exploitation of Helianthus tuberosus unviable.

The other species with a considerable content of inulin belong to the genus Cichorium, and are commonly known as chicory. However, the strong tasting of the roots of Cichorium species limits its use as a source of sweeteners. Instead, they are used as substitutes for coffee.

The tuberous roots of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, on the other hand, look like enormous swelled fingers, so that their processing results easier. The yield of Smallanthus sonchifolius is also bigger than Helianthus tuberosus, and its fresh tuberous roots contain almost 19% of inulin (Calvino, 1940) or inulin-related compounds.

Compared with its competitors, Smallanthus sonchifolius has the advantage of not only producing high yields and probably being easier to harvest and process, but also providing additionally a special food in the form of animal fodder, the latter due to the high content of protein in its leaves (between 11% and 17%, dry weight). Because all of this, Smallanthus sonchifolius easily could be the equivalent for sugar beet, but for the production of fructose sugar.

2. Yacon Description

Habit: Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson is a perennial herb, compact and rough-textured. This herb rises up to 1.5 m to 2 m in height –although some individuals can reach up to 2.5 m and even 3 m tall—. Two kinds of stems are present in this plant species: aboveground and underground.

The aboveground stems are thick, cylindrical or a little angular, striated, densely pilous –especially on the upper part—and with purple lines. These stems tend to radially incline from the centre to the outside, at a distance equivalent to their height. Although succulent when young, they tend to harden (lignify) and form a hole through their central axis as they get older. When dry, they commonly acquire a yellowish-orange color.

The underground stems form a system of short, thick, and sympodial rhizomes, and are used in order to vegetatively propagate this plant species. Although they are not usually eaten, these rhizomes are edible.

Leaves: The leaves are opposite, dark-green, large, and variable in shape. The lower leaves are widely ovate and hastate or sub-hastate, up to 33 cm long and 22 cm wide. They are pinnatifid, with short lobes that are separated by wide and not much deep sinus. Their margin is dentate, and the teeth have calli at their tips. The base of the expanded portion of the leaf blade is triangular or abruptly cuneate. The petiole possesses wings up to 4 cm wide and 14 cm long. At the base, the lower leaves are auriculate and connate. They present 3 main veins.

The upper leaves are ovate-lanceolate, with no lobes or hastate bases, and with densely glandulous-pilose petioles. Both, the adaxial and abaxial leaf faces of all the leaves, present trichomes (0.8 mm to 1.5 mm long, and 0.05 mm in diameter) and glands containing terpenoid compounds.

The phyllaries (bracts) are 5, green, uniseriated, ovate or ovate-lanceolate, sharp-pointed, up to 15 mm long and 10 mm wide, glandulous-pilose at the base, almost glabrous at the top, and with pilose margins.

Flowers: The flowers are somewhat scarce, which is a common feature among clonally propagated tuberous crops. They are arranged in capitula (heads) that are born on 1 to 5 axes, each one with 3 capitula on densely pilose peduncles. These inflorescences are terminal. Its delicate flower heads are small, approximately 2.5 cm in diameter, similar to common daisy, and yellow or light orange. They are located at the upper part of the plants and on additional stems that emerge from the lowermost leaf axils; these flowers are not much conspicuous, and look a little strange among the enormous leaves.

The external flowers (ray flowers) are up to 15 and have a pistil. They have long ligules, 10 mm to 15 mm long, and 7 mm wide, yellow or orange, bidenticulate or tridenticulate at the apex, and a tube densely pilose on the outside.

The central flowers (disc flowers) are staminate, tubular, and between 7 mm to 8 mm long. The corolla is yellow and slightly pubescent on the outside. The paleae of the corolla are ovate-lanceolate, near 6 mm long, and 2 mm wide. The paleae of the disc are obovate, with the upper margin denticulate, near 3 mm long and 2 mm wide.

Fruit: Achene, purple when immature and dark brown or black when mature. Seed formation is very rare. Even when produced, a high percentage of the seeds result unviable or show a low vigor.

Roots: The radical system of Smallanthus sonchifolius is densely ramified. It is constituted by a vast system of cylindrical roots (non storage roots) and tuberous roots (storage roots) of adventitious nature. The latter ones are pretty irregular in shape, between spindle-shaped and round-shaped (a little similar to those of the common dahlia), and can vary considerably with respect to shape, size, and sweetness. The youngest ones tend to be more sharp-pointed at both extremes. The fully mature ones can reach up to 30 cm in length –although they commonly measure between 15 cm and 20 cm—and 10 cm in diameter, and got fused at their point of origin to the underground swelled rhizomatous stem.

The irregularity of its shape many times is due to the contact with stones in the soil or the pressure of neighbor tuberous roots. Four, 5, or even 20 tuberous roots can be disposed around the stem base, just beneath the soil surface, pointing outside as a manner of rays in a bicycle wheel –although tremendously thicker—emerging from its centre.

Externally, the tuberous roots can be brown, pink, purple, cream, or ivory, with a skin between 1 mm and 2 mm thick that easily separates from the root by friction and contains resiniferous conducts plenty of yellow crystals Internally, they are white-, cream-, yellow-, purple-, or pink-colored, some times white with purple striae. The pulp is fleshy, finely fibrous, crunchy, amazingly sweet, a little juicier than apple, refreshing, and translucent when seen against the light.

Generally, each tuber weights between 200 g and 500 g, although they can reach up to 2 kg. Because of its flavor and texture, this root has been compared to a combination of apple and watermelon. Left under sunlight, they turn sweeter. The thickening of the storage roots is owed to the proliferation of parenchymatous tissue in the root cortex and particularly in the vascular cylinder. The parenchyma accumulates sugars and, in certain cases, pigments.

As other Compositae (=Asteraceae) species, the roots of Smallanthus sonchifolius synthesize inulin or inulin-related compounds, although not starch (Bredemann, 1948). Effectively, spherocrystals typical to inulin have been found in the parenchyma of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson.

3. Yacon Origin, Distribution and Ecology

Origin: Smallanthus sonchifolius originated in the Andes. Many wild species related to this plant species show a clear preference for disturbed habitats, such as river shores, terrains dragged by floods, and roadsides.

The habit of this plant species is well adapted in order to take advantage of terrains cleared of vegetation. The strategy of colonizing areas free of vegetation could be the reason by which Smallanthus sonchifolius got associated with humans for the first time.

Agriculture on the steep slopes in the Eastern Andes, particularly ‘cut and burn’ agriculture practiced by people in the Andes since prehistoric times, could have supported an ideal niche for the ancestral relatives of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson.

Today, this behavior can be observed in the watershed of the Vilcanota River, where Smallanthus siegesbeckius is a common invader of abandoned fields and a common weed in coffee plantations. The same strategy is used by Smallanthus macroscyphus, in northwestern Argentina, where it invades abandoned sugar cane plantations, as well as free space between the parcels of land. It seems highly possible that a hybrid of two or more Smallanthus species accustomed to colonize disturbed habitats has originated an ancestral form of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson.

It is possible that Andean peasants have discovered the properties of Smallanthus sonchifolius since the beginning, by which they changed its status of weed to managed plant and then cultivated plant. The most probable area were this action took place corresponds to the humid slopes of the Eastern side of the Andes, in a region that extends from North Bolivia to Central Peru, which is the area with the most clone diversity and where native names are used, Quechuan and Aymaran.

Although mountainous forests in Central Peru and North Bolivia are evergreen forests supplied with abundant rain water during most of the year, they are subjected to a relative dry winter season of between 2 and 4 months of duration. This dryer and slightly cooler interval could have played a crucial role on the evolution of Smallanthus sonchifolius by generating conditions by which a plant species with big tuberous roots could have an adaptive advantage.

The centre of origin for Smallanthus sonchifolius seems to be a narrow band of land along the Eastern slopes of the Andes, from the Apurimac river watershed (12º S) in Peru, toward the La Paz River watershed (17º S) in Bolivia. This zone is where most of the germplasm diversity of Smallanthus sonchifolius is found, and is also the place where 3 wild species closely related to Smallanthus sonchifolius grow spontaneously (Smallanthus macroscyphus, Smallanthus riparius and Smallanthus siegesbeckius).

Distribution: Smallanthus sonchifolius grows in Colombia, Ecuador, Peru, Bolivia, and northwestern Argentina, and is commonly found naturalized at moderate altitudes –approximately 2 000 m asl.— in South America, especially in the yunga region, on the western face of the Andes, or in the cloud forest, in tropical and subtropical weathers, on the Eastern slopes of the Andean Mountain Range, from Venezuela to northwestern Argentina. The altitudinal limit within this region seems to be 3 300 m asl.

From the humid and mountainous forests of Peru and Bolivia, Smallanthus sonchifolius could have expanded toward North and South along the humid slopes of the Andes, toward the dry Interandean valleys of the Andes, and toward the Peruvian Coast. The dry Peruvian Coast is precisely the place where the most ancient graphic representations have been found.

This species was lately introduced to Ecuador, maybe by the Incas, a few decades before the Spaniards arrived.

Areas of Traditional Cultivation: Smallanthus sonchifolius is, typically, a self-subsistence crop, so that this plant species is commonly cultivated in small domestic parcels of land. In some zones within its area of ancestral distribution, almost everybody has at least some few plants in their domestic parcels of land, and cultivate this plant species as dainty.

In Northern Argentina, Smallanthus sonchifolius is extensively cultivated; whereas in Latacunga, Ecuador, this plant species is sold in big amounts, especially as a tradition during the Day of the Dead. Contrarily, in some other areas, Smallanthus sonchifolius is rarely seen in the markets; in some places, it is almost unknown. Its forlornness is related to the absence of an intensive technique of production whose origin can be tracked up to the fact that this plant species is not commonly eaten in the urban areas.

In Colombia, Smallanthus sonchifolius grows up in Cauca, in the Cundinamarca Plateau, Boyacá, and Nariño, between 2 600 m and 3 000 m asl., over the high and deserted tablelands  (Rea, 1994).

In Ecuador, this plant species grows up between 2 400 m and 3 000 m asl., spontaneously in the fields plenty of maize and in orchards in the Interandean belt with the following order of importance: Loja, Azuay, Cañar, in the environs of the Lake San Pablo, Imbabura, and Bolívar province. Smallanthus sonchifolius also grows in Chimborazo, Pichincha and Tungurahua.

In Peru, the cultivated varieties are found between 1 300 m and 3 500 m asl., with the most concentration in Northern and Southeastern Sierra, among 2 000 m and 3 000 m asl. Smallanthus sonchifolius has been found in Pre-Incan tombs, which indicates that since ancient times the diffusion of this plant species was broad.

In Bolivia, Smallanthus sonchifolius grows near 2 500 m asl., with a maximal altitude of 3 600 m asl. at the head of the valley in Northern La Paz (provinces of Larecaja, Camacho, Muñecas, Bautista Saavedra), in Cochabamba de Pocona toward the South, Chuquisaca, the mesothermal valleys of Santa Cruz and Tarija. In this country there exist numerous varieties.

In Argentina, Smallanthus sonchifolius grows up in northwestern Jujuy, where it is cultivated in small domestic parcels of land along the Andean misty forest. Although in old times it was extensively cultivated, today Smallanthus sonchifolius almost is unknown in Salta province (Zardini, 1991). In the same city of Salta there exist a street and a town called “Los Yacones”, which remembers and important past for this plant species. It is considered a strange crop, and there are only known 1, 2 or maybe 3 varieties.

This plant species grows rapidly and easily, and even can survive in poor soils. Smallanthus sonchifolius is not restricted to highlands; it has proved to grow excellently at sea level. It has been said that the production of Smallanthus sonchifolius got increased during the generalized drought that devastated the Andean region during 1982-1983, when the production of potato –which resulted seriously affected—was replaced by Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, with good results (Rea, 1994). However, less than one million people are thought to use this plant species in the Andes (Hermann & Heller, 1997). As a matter of fact, this crop is unknown for most of the Andean inhabitants, and scarcely reaches the markets of the zone.

Out of the Andes, Smallanthus sonchifolius is almost unknown, despite of having been taken to Europe a hundred years ago. However, the last years –and, especially, after the publication in the United States of the book Lost Crops of the Incas, in 1989—a considerable interest for Smallanthus sonchifolius has arise due to both, its therapeutic properties and its flavor. Hence, the cultivation of Smallanthus sonchifolius spread to New Zealand –the first country that produced it commercially—and from there to Japan; and from Japan, it went to Brazil –where nowadays it is cultivated in large scale—and Korea.

Genetic Diversity: The IICA started to collect Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson in 1963. Since then, in Peru 200 collections have been obtained, especially in Cajamarca.

In Ecuador, 32 collections have been procured; furthermore, a wild form has been found. The best time to collect is from June to August. A preliminary evaluation of sugar content has been carried out in 10 clones.

In Bolivia, 2 varieties are predominant: one with red anthocyanin spots, and other without spots (Cárdenas, 1950). However, there exist 32 morphotypes.

In Argentina, only one variety is known.

The most common cultivars in each country –white, purple, and yellow—coincide with the color of the edible part of the roots; the yellow one is the most wanted.

4. Yacon History

Since time immemorial, Smallanthus sonchifolius has been recognized as a food of relatively low energy, in spite of its sweetness. Its value has been linked to its high productivity, agreeable tasting, and medicinal properties more than its properties as food. Hence, This plant species has been considered mainly as a secondary crop.

Today, the way we consider Smallanthus sonchifolius could be radically different from that of the past. The caloric intake in many regions of the world still remains critic –the Andean region included--; however, worldwide, sugars and carbohydrates are relatively cheap foods that are available in high quantities for certain sectors of the human population, even in very higher quantities than their dietary requirements, and even beyond their physiologic tolerance. Hence, Smallanthus sonchifolius could supply a low-calorie diet, as well as the fiber, necessary in order to overcome the stress of a sedentary life-style and the excess in the intake of carbohydrates and fats.

The oldest known representation of Smallanthus sonchifolius correspond to clusters of roots identified in the Nazca art, pertaining to the early period (500 – 1 200 A. D.), both in textiles (O´Neal and Whitaker, 1947) and huacos (Safford, 1917). Yacovleff (1933) assures that Smallanthus sonchifolius  is found in almost all the funerary bales of Paracas.

Southernmost, in Northwestern Argentina, dry roots have been identified and recovered from Pampa Grande, Serranía Las Piraguas, Guachipas, Salta province (collection of the Museum of La Plata, Argentina) associated with culture Candelaria, which developed between the years 1 and 1000 A. D., southward the present area of cultivation (Zardini, 1991).

The first mention about Smallanthus sonchifolius was written by Felipe Guaman Poma de Ayala in 1615, in a list of 55 native crops. He denominated it as llacum.

The first written register of Smallanthus sonchifolius was made by chronicler father Bernabé Cobo in 1653 (book IV, chapter XVI: 365-366): “They are eaten raw as fruits and possess an agreeable tasting, and a more agreeable one if exposed to sunlight until dry. This is a marvelous fruit to put on board, because it lasts a long time. I have seen it put on board during more than 20 days and, with respect to its juiciness, it became sweeter and was refreshing during warm periods”.

In the 19th century, Weddell (1857) called the attention on the qualities of the roots of Smallanthus sonchifolius and denominated it Polymnia edulis. This plant was exhibited in Europe for the first time by Triana, in the exhibition of Paris in the early 20th century, under the name of jiquimilla, although it does not attracted much attention (Pérez Arbeláez, 1956).

However, a visionary Italian agronomist called Mario Calvino was the one who initiated the cultivation of Smallanthus sonchifolius in Europe, before World War II, in the temperate lowlands of Sanremo, Italy, where this plant species prospered vigorously. He met Smallanthus sonchifolius by chance, while he was working in the Dominican Republic, and decided to take some tubers to Northern Italy, hoping the plant become a high-protein content palatable fodder, as well as a possible source of sugar in order to produce alcohol as fuel.

From Calvino’s fields, Smallanthus sonchifolius spread to other zones in Southern Europe, although with scarce success. Hence, the cultivation of this plant species in order to produce alcohol and inulin from its roots, as well as fodder and vegetables from the whole plant, resulted successful in Italy, although not in Germany Bredemann, 1948). However, war interrupted abruptly its diffusion. After the war, Calvino and his plant were forgotten.

In an extended area comprising from Peru to Argentina, Smallanthus sonchifolius continued being eaten traditionally, particularly during Corpus Christi, Christian celebration that displaced the K’apac Raymi celebration during Inca times (Cárdenas, 1969).

In Ecuador, the tuberous roots of Smallanthus sonchifolius are eaten especially during the holydays of ‘Día de todos los Santos’ and ‘Día de los Muertos’ (National Research Council, 1989).

In some regions of Peru, Smallanthus sonchifolius is eaten during Holy Week, in the form of thick slices, and sugarcane aguardiente; this is called fresco de velorio. These practices could be an evidence of the modification of ancient religious values after the arriving of the Catholic Church.

Until relatively a short time ago, the cultivation of Smallanthus sonchifolius was declining slowly and constantly throughout the Andes. Fortunately, during the 1980 decade, a dramatic international change of mind related to this crop occurred, particularly after the release of the book Lost Crops of the Incas (National Research Council, 1989).

Today, in New Zealand some farmers are offering Smallanthus sonchifolius to amateur gardeners and for commercial planting, and its tuberous roots are being packed the same way as carrots are packed and are sold in supermarkets.

Smallanthus sonchifolius has been satisfactorily reintroduced in Southern Europe, although it has not been broadly spread. Only recently this plant species has been introduced in the United States of North America, where it prospers thanks to amateur cultivators in several states, such as California, Oregon, New Mexico, Florida, Alabama, and North Virginia, among others.

Smallanthus sonchifolius is also rapidly becoming popular in the Far East. In Japan, especially in Hokkaido, this plant species carried from New Zealand is becoming popular as ‘exotic food’, and some farmers are beginning to cultivate it. From Japan it has been introduced to Korea and Brazil. In Brazil its commercial cultivation has already started in the state of São Paulo.

5. Yacon Uses

Parts Used:

Tuberous roots, aboveground stems, leaves, rhizomes.

· Tuberous roots: The tuberous roots are sweet and edible. Its flavor results agreeable for a wide range of people, and has been compared to a combination of apple and watermelon, not only because of its sweetness, but also for the consistency of its pulp. The tuberous roots are customarily eaten raw, especially after exposure to sunlight until the skin gets corrugated, during a period that varies according to the region.

The exposition to sunlight –called chochascca in some regions of Peru (Herrera, 1943)—increases its sweetness. This provokes that in many recondite zones of the Andes these roots are considered –especially by children—as a delicatessen. In the local markets of the Andes, the tuberous roots of Smallanthus sonchifolius are not sold together with potatoes, ocas, and ollucos, as it could be expected, but as if they were fruits, together with cherimoyas, apple pines, apples, avocados, etc.

The tuberous roots are eaten raw but peeled, since their skin is quite resinous. In slices, the tuberous roots result particularly delicious in fruit salads, together with bananas, oranges, papayas, etc. They are also added to vegetable salads, by which flavor and texture is imparted. Furthermore, these roots can also be smashed altogether with carrots and raisins in order to prepare a healthy sweet salad with cabbage.

The tuberous roots are also eaten boiled and baked. When they are boiled with water, the skin separates from the flesh, so that the roots can be peeled easily. Cooked, they maintain sweet and slightly crunchy. These qualities are becoming Smallanthus sonchifolius popular for a series of Oriental dishes, especially in those places where ingredients of the Oriental Cuisine are scarce.

In the Peruvian Andes, they are frequently grated and then squeezed through a piece of clothes in order to obtain a sweet and refreshing drink. Sometimes this liquid is concentrated in order to obtain brown blocks of chancaca de yacón, the same way they do with the juice of sugarcane.

They can be also used as food for cattle since, contrarily to what occurs with humans, ruminants do can metabolize easily all the carbohydrates present in them, including oligofructans or inulin-related sugars, thanks to microorganisms present in their stomach. Finally, the tuberous roots can also be used as source of fructose and to produce alcohol.

Chemical Composition: The tuberous roots of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, similarly to any other tuberous root or stem, are a natural depot for carbohydrates whose purpose is to serve as a reserve for the plant. According to the National Research Council (1989) of the United States, the analysis of fresh tubers of Smallanthus sonchifolius resulted as follows:

Humidity:   69%-83%

Carbohydrates (mainly inulin-type compounds     20%

Protein        0.4%-2.2%

The analysis of the dry tubers, according to the same study, resulted as follows:

Carbohydrates (mainly inulin-type compounds)    ± 65%

Protein         6%-7%

Ash              4%-7%

Fiber            4%-6%

Fat              0.4%-1.3%

Most roots and tubers store carbohydrates in the form of starch, a glucose polymer; Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, on the other hand, stores carbohydrates in several ways: fructose, glucose, sucrose, low polymerization degree oligosaccharides, DP3 to DP10 fructans; DP= degree of polymerization) and traces of starch and inulin (Asami et al. 1989; Ohyama et al. 1990).

Inulin is a high polymerization degree oligofructan, with a polymerization degree or PD=35, approximately, and, besides, one of the most important storage compounds for many plant species within the family Compositae (also called family Asteraceae) such as Helianthus tuberosus y Dahlia sp. However, in Smallanthus sonchifolius inulin appears to be a minor component. On the other hand, oligofructans with a lower degree of polymerization (4.3, on average), seem to represent up to 67% of the dry matter content of Smallanthus sonchifolius at harvest (Asami et al. 1991).

Oligosaccharides purified from Smallanthus sonchifolius have been identified as β-(2-1)-fructooligosaccharides with terminal glucose (inulin-type oligofructans; Goto et al., 1995). The relative proportions of oligofructans and monosaccharides fluctuate significantly during the growing cycle of the plant and after harvesting (Asami et al., 1991; Fukai et al., 1995), resulting in apparently contradictory results. For example, a detailed dry weight analysis of the soluble carbohydrates present in the tuberous roots of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, 96 days after harvested and maintained in cold conditions resulted as follows (Ohyama et al., 1991):

Fructose                  350 mg/g

Glucose                  158 mg/g

Sucrose                   74 mg/g

GF2                        60 mg/g

GF3                        47 mg/g

GF4                        34 mg/g

GF5                        21 mg/g

GF6                        16 mg/g

GF7                        13 mg/g

GF8                        10 mg/g

GF9                        7 mg/g

Total GF2-9            201 mg/g

GFn= fructosylsucrose; n indicates degree of depolymerization

This analysis indicates that oligofructans represent only 20%, instead of 67%, as reported by Asami et al. (1991). However, it is important to note that Ohyama and coworkers used material that had been stored in cold conditions for more than 3 months, whereas Asami’s team used roots immediately after harvest. Unfortunately, an important amount of information about the sugars in the storage roots of Smallanthus sonchifolius is written in Japanese, so that its diffusion is restricted.

Besides the carbohydrates, the tuberous roots of Smallanthus sonchifolius contain small amounts of fiber, vitamins, and minerals.

· Aerial stems: The eating of the tender aerial stems as cook vegetable has been reported (National Research Council, 1989). When mature, they could be used as fodder for cattle, since they have a good content of protein. Besides, when cut, the foliage sprouts again from the underground stems; this fact turns Smallanthus sonchifolius an excellent pasture. However, there does not exist experimental information concerning this use. Terpenoid lactones produced by epidermal glands on the leaves could affect the palatability of the foliage.

Chemical Composition: Calvino (1940) reported 11% of protein content (dry weight).

· Leaves: Leaves are said to be eaten as vegetable, when cooked. Kakihara et al. (1996) have reported the use of a 5% dry leaf infusion, as a kind of tea, drunk as antidiabetic; it is, as a reducer of glucose blood levels or hypoglycemic. Moreover, the use of leaves as fodder for cattle has been suggested because of its high content of protein. However, and similarly to what occurs with the stems, there is no experimental information concerning this fact. Terpenoid lactones produced by epidermal glands on the leaves may affect their palatability.

Chemical Composition: According to the National Research Council of the United States (1989), the chemical composition of dry leaves is as follows:

Protein                                11%-17%

Fat                                      2%-7%

Nitrogen-free extract          38%-41%

Calvino (1940) assigns them 17% of protein content.

· Rhizomes: Although they are not usually eaten, rhizomes are edible (Zardini, 1991). In practice, they are currently used in order to reproduce the plant as a clone.

Properties:

Smallanthus sonchifolius is used as/for/against:

• alcohol
• antidiabetic
• antifungal
• cancer preventive factor
• cholesterol reducer
• dietetic sweetener
• digestive
• favors assimilation of calcium
• food (for animals)
• food (for humans)
• hypoglycemic

pesticide

• renal diseases
• several of its sugars are not cariogenic (they do not produce caries)
• skin rejuvenating
• soil protector
• source of fructose
• stimulates synthesis of vitamins of complex B
• triglycerides reducer

Among the several lost crops of the Andes, maybe Smallanthus sonchifolius is the most promising species due to its surprisingly wide range of advantages (National Research Council, 1989). The use of this plant ranges from sweetener syrups and prickles to dry flakes and leaf tea. The interest in Smallanthus sonchifolius has been fueled because of the discovery of dietetic sugars in its roots (mainly fructans) and putative medicinal compounds in the leaves.

Dietetic Sweetener and antidiabetic

Most roots and tubers store carbohydrates in the form of starch, a glucose polymer. The tubers of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, on the contrary, store carbohydrates in the form of inulin-type sugars; it is, fructose polymers that the human body can not metabolize due to lack of the appropriate enzymes. This means that the sugars in Smallanthus sonchifolius can pass throughout the human digestive tract almost unaltered, until they are evacuated with feces. Hence, the roots of Smallanthus sonchifolius provide scarce calories (4-10Kj/g). For this reason, the sugars present in these roots are an acceptable sweetener for dieters and diabetics. The tuberous roots of Smallanthus sonchifolius store great amounts of these inulin-type sugars.

The tuberous roots of Smallanthus sonchifolius can be eaten raw, since they are sweet and delicious; but, in order to obtain a sweetener that can be used to sweet other products, the roots have to be processed. First, the roots have to be pressed until all its juice is drained. Then, the so obtained juice is to be concentrated by heat, until a solid, dark-brown colored block is obtained; this block is called chancaca de yacón, because of its similarity with chancaca, a solid block of raw brown sugar obtained from sugarcane.

This juice can also be concentrated at low pressure and with sodium bisulphate; these factors prevent the darkening of the syrup by enzymatic activity. The final product is a dense, crystalline syrup similar to that obtained from sugarcane, although with a significantly lesser caloric value (Chaquilla, 1997).

Hypoglycemic

Besides being used as sweetener for diabetics, Smallanthus sonchifolius is also being used in order to reduce blood levels of glucose (hypoglycemic). In Brazil, Kakihara et al. (1996) attributed these properties to the leaves. There, a 0.5% (mass-volume) medicinal tea is prepared from dry leaves. The dehydrated leaves of Smallanthus sonchifolius  are also used in Japan, in order to produce a medicinal tea mixed with leaves of common tea.

Volpato et al. (1997) have scientifically proved the hypoglycemic activity of a water extract obtained from dehydrated leaves of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, in rats with induced diabetes. The hypoglycemic effect of the water leaf extract has also been shown in rats by Aybar et al. (2001). Leaf-infusion has been affirmed to reduce in 10 days sugar levels from 348 mg/dl to 214 mg/dl in rats.

Digestive

In almost all the places where it is cultivated, Smallanthus sonchifolius is considered a desirable component in diets for sick and weak individuals. The low polymerization degree oligofructans present in the tuberous roots are not hydrolyzed by human digestive enzymes or absorbed in the upper part of the gastrointestinal tract. Instead, they arrive almost intact to the large intestine. In the colon, the fermentation of these low polymerization degree oligofructans produces short chain fatty acids that could be important in order to maintain the well functioning of the epithelial cells, thus preventing their carcinogenesis; moreover, they diminish pH of the colon.

Inulin and oligofructans in general are also said to play a role as prebiotics, substances that selectively feed and stimulate the beneficial germs commonly present in our intestinal flora, such as the so called bifidobacteria, favoring their growing and stopping the development of prejudicial microorganisms, such as Clostridium. Therefore, the inulin and oligofructans present in Smallanthus sonchifolius may be important in order to resist colonization and as prophylaxis for gastrointestinal disorders.

Bifidobacteria, at a time, can alleviate hyperlipemia, that is to say the increase of lipids in blood (cholesterol and triglycerides). Moreover, bifidobacteria are believed to favor the development of Bacillus subtilis in the colon, and avoids the growing of putrefactive microorganisms which tend to produce diarrheas. Additionally, they control constipation and increase excretion.

Food for Humans

Smallanthus sonchifolius has a limited nutritional value. Despite this, almost all the plant can be eaten by humans: aboveground stem, leaves, rhizome or underground succulent stem, and, of course, the tuberous roots.

The main stem of this plant is used as a cooked vegetable, provided that is tender, since when mature, it hardens and results inappropriate for eating. The cooked leaves have also been reported to be edible. The nutritional value of the stem and leaves for humans is unknown.

The most interesting part of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, from the point of view of human nutrition, is constituted by its tuberous roots. These roots taste good and usually are eaten raw, as a fruit; especially, after exposure to sunlight for several days, until the skin corrugates. The exposition to sunlight makes them sweeter, although they can result less crunchy. On the other hand, the skin may have a resinous flavor, so that the tubers are peeled before they are eaten.

Although it has few calories and scarce nutritional value, Smallanthus sonchifolius is finding its way in cookery around the world, especially in the Asiatic one. Effectively, this sweet and crunchy root is sliced and added to salads, thus imparting flavor and texture. They can also be milled together with carrots and raisins in order to obtain a healthy cabbage salad. The tuberous roots are also eaten boiled and baked. If they are boiled with their skin, it will separate from the flesh, thus the roots can be easily peeled. Cooked, they maintain sweet and slightly crunchy. This fact is turning them popular for a series of Asiatic dishes.

In the Peruvian Andes, these roots are frequently grated and then squeezed using a piece of clothes in order to obtain dark-brown colored blocks of chancaca de yacón, the same way the juice of sugarcane is treated.

In Japan, Smallanthus sonchifolius is already being commercially exploited in a great variety of processed products, such as pickled slices and dehydrated slices. In Brazil, chips of the roots of Smallanthus sonchifolius are being produced. In order to do this, the tuberous roots are peeled and finely sliced. These slices are first dehydrated in a plastic tunnel and then dried more in an oven at 60º C (Kakihara et al., 1996). Once dehydrated, these chips can be preserved indefinitely.

The pulp of Smallanthus sonchifolius can be preserved doing the following. Heat up to 89º C during 10 minutes; rinse with sodium bisulphate (0.5%) for 10 minutes; add potassium sulphate (0.1%), ascorbic acid (0.3%) and adjust pH in 4.5. The so treated pulp can be used with sugarcane honey in order to prepare ‘glazed yacon’, the same way fruits are glazed.

Source of fructose and alcohol

Japanese scientists are studying Smallanthus sonchifolius as a probable source of fructose purified in the form of fructose syrup. Smallanthus sonchifolius could easily be the equivalent of sugar betel, but for the production of sugar fructose. The fructose obtained could be easily fermented in order to produce alcohol, as it has been suggested.

Food for animals

Smallanthus sonchifolius could have a potential as fodder crop. Its foliage is exuberant, and the leaves have a protein content of 11% to 17% dry weight. Once cut, foliage sprouts again from the underground stems; this turns Smallanthus sonchifolius an excellent pasture. However, no experimental information relative to this use exists. Terpenoid lactones produced by the epidermal glands on leaves may affect palatability of the foliage.

The tuberous roots may also be a good food for cattle, since contrarily to what occurs with humans, ruminants do can metabolize easily all the carbohydrates present in the roots, including oligofructans or inulin-type sugars, due to microorganisms present in their stomachs. On the other hand, pigs are said to be able to eat them, although it is unknown if they can metabolize the roots, since pigs are not ruminants.

Soil protector

Smallanthus sonchifolius can also be used as soil protector due to its ability to maintain as a perennial species, especially in dry agroecological zones. Additionally, Smallanthus sonchifolius could be used in agroforestery, since it grows well under canopy shadow.

Antifungal and pesticide

The leaves of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson have an inhibitory activity against the production of aflatoxins B1 and B2 (E. Gonçales et al., 2003). Aflatoxins are a group of fungal toxins produced by strains of the fungi Aspergillus flavus and Aspergillus parasiticus. These species are known to contaminate a variety of foods and aliments. The interest in aflatoxins has focused in aflatoxin B1, principally due to its huge chronic toxicity and carcinogenic activity in animals and probably in humans.

The leaves of Smallanthus sonchifolius are highly resistant to pests because of the antifungal compounds they produce (Inoue et al., 1995). Pinto et al. (2001) have shown the inhibitory activity of the water extract obtained from its leaves on the production of aflatoxins B1 and B2. Gonçales et al. (2003) have shown the inhibitory activity of the ethanol extract obtained from the leaves on the growing of Aspergillus flavus, the production of aflatoxins B1 and B2, and its cytotoxicity.

Cancer preventive factor

Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson has also been considered cancer preventive factor. The water (Pinto et al. 2001) and ethanol (E. Gonçales et al., 2003) extracts obtained from leaves of this plant species are known to have inhibitory activity for the production of aflatoxins B1 and B2. These toxins, produced by fungi, contaminate a wide variety of foods and aliments and type B1 is thought to have carcinogenic activity. On the other hand, it has been claimed that fermentation of inulin-type sugars in the colon produces short-chain fatty acids that could be important in order to maintain the normal function of epithelial cells, thus preventing their carcinogenesis.

Other properties

Ability to treat renal disorders, rejuvenate skin and counteract high cholesterol and triglycerides blood levels have also been attributed to Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, although they have not been completely demonstrated. This plant species is also said to favor calcium assimilation and stimulate synthesis of vitamins of complex B, and that many of the sugars present in it do not generate caries.

Phytochemicals:

• alpha-glucose
• beta-glucose
• fructose
• inulin
• inulin-type sugars (oligofructans)
• sucrose

Inulin-type sugars (oligofructans)

Roots of Smallanthus sonchifolius store a series of carbohydrates. Inulin, a high polymerization degree oligofructan (PD=35, approximately), is a main storage compound in many plants within the family Compositae, such as Helianthus tuberosus, “Jerusalem artichoke”, and Dahlia sp., “dahlia”. However, in Smallanthus sonchifolius inulin appears to be a minor compound. Instead, this plant species concentrates a series of lower polymerization degree oligofructans (PD=4.3, on average) that may represent up to 67% on a dry matter basis at harvest (Asami et al., 1991).

The oligosaccharides purified from Smallanthus sonchifolius have been identified as β-(2-1)-fructooligosaccharides with terminal sucrose, which makes them inulin-type oligofructans (Goto et al., 1995). The relative rates between oligofructans and monosaccharides fluctuate significantly during the growing cycle of this plant and after harvest (Asami et al., 1991; Fukai et al., 1995). Ohyama et al. (1991) have reported that 96 days after harvest, oligofructans represented only 20% on a dry weight basis, instead of 67% at harvest, as Asami et al. reported (1991).

Low polymerization-degree oligofructans are –as inulin– in the category of non-digestible foods. Being non-digestible, these compounds are not assimilated and do not supply any calorie. Hence, low polymerization-degree oligofructans are not hydrolyzed by human digestive enzymes nor absorbed in the upper part of the gastrointestinal tract. The fermentation of oligofructans in the colon produces short-chain fatty acids that may be important in order to maintain the correct functioning of the epithelial cells thus preventing colon carcinogenesis; moreover, this fermentation diminishes pH in the colon. Selective fermentation of oligofructans by microorganisms in the colon results in stimulation of bifidobacteria, which inhibit the growing of potentially pathogenic species such as Clostridium. This bifidobacteria may be important for resisting colonization and prophylaxis of gastrointestinal diseases.

Fructose

Free fructose is a non-reducing monosaccharide with a ketonic group; whereas glucose has an aldehyde group and is reducing. In the past, the major commercial sweetener was crystalline sugar, and fructose –the latter one being hard to obtain in a crystalline form– had little interest. Today, syrups rule the industrial use of sugars and fructose leads the industry. The greater interest in fructose-rich sweeteners of today could turn Smallanthus sonchifolius economically more adequate than never before. Certainly, the “super rich fructose syrups” obtained from inulin could have an intrinsic value in addition to the diluents for elevating fructose levels in the normal syrups.

In recent years, fructose has received much attention as sweetener agent. Its sweetening strength is two times the one of common sugar (sucrose). Until now, fructose is being produced by means of enzymes that transform the glucose obtained from corn syrup. Most “fructose-rich corn syrups” contain less than 60% fructose. With Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, however, no transformation of one sugar into other would be needed, and the resulting syrup would contain probably more than 90% fructose.

Solids in these roots could be up to 60% to 70% inulin-type sugars (oligofructans), which are easily hydrolyzed –by an acid or the enzyme inulase– to fructose. In spite of the previous interest for using inulin to obtain fructose, few has been done in order to make it real. The roots of Smallanthus sonchifolius might be crucial for turning this process economically attractive.

Other monosaccharides

The average monosaccharide content of fresh roots has been estimated in (Rea, J., 1994):

Fructose      2g/100g

α-glucose    2g/100g

β-glucose    2g/100g

Sucrose       2g/100g

The average content increases as sugar content concentrates in roots exposed to sun for 2 weeks:

Fructose      22g/100g.

α-glucose    7g/100g

β-glucose    6g/100g

Sucrose       4g/100g

As occurs with sugarcane, the monosaccharides present in Smallanthus sonchifolius can be concentrated in order to obtain sugar or molasses. The conversion of these sugars into alcohol has also an agroindustrial potential.

Inulin

Inulin has a neutral soft flavor, is moderately soluble in water and supply structure and palatability. Inulin has a great capacity for replacing fats. When mixed with water, inulin forms a creamy gel with excellent palatability. The molecule of inulin present in the roots of Smallanthus sonchifolius has not been characterized yet, although in related species (other Compositae members) it has a molecular weight between 3 000 and 5 000 daltons. Inulin is a polymer of fructose, but with a terminal unit of glucose. Hence, inulin contains a small amount of glucose.

Recent studies (Asami et al. 1989; Ohyama et al. 1990) suggest that, contrarily to what occurs with other plants within the same family, Smallanthus sonchifolius would accumulate only small amounts of inulin. Instead, there would be a series of inulin-type compounds of a lower degree of polymerization, although with the same properties.

6. Yacon Cultivation

· Environmental Requirements.- There exists very few information relative to the environmental requirements of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson. However, according to field observations, requirements are as follow:

Light.- Smallanthus sonchifolius develops well under both partial shadow and full sunlight.

Photoperiod.- This plant species is neutral for stem and tuber formation. However, the formation of tuberous roots begins later in higher latitudes. On the other hand, in warm regions, flowers are not produced unless the daylight period is shortened during autumn.

Rainfall.- Its annual foliage and perennial underground stems turn Smallanthus sonchifolius an adaptable plant species for seasonal cycles of droughts and frosts. Because of its growing habits, it requires humidity during the first stages, but subsequently can tolerate drought periods.

Altitude.- Commonly, among 900 m and 2 750 m asl., in the Andes, although Smallanthus sonchifolius has also been grown at sea level both in New Zealand and the United States, and recently in Japan and Peru (there does not exist information about the production of edible roots, except in New Zealand, where this plant species is cultivated commercially).

In Ecuador, Peru and Bolivia, Smallanthus sonchifolius has been reported up to 3 500 m asl. In Argentina, it grows between 600 and 2 500 m asl. In Brazil, this plant species is being cultivated at 600 m asl. Farmers in Argentina and South Bolivia indicate that moderate altitudes (1 500 m to 2 000 m asl.) are the best for tuber roots formation, whereas lowlands, which are warmer, are better for “seed” production (rhizomes).

Temperature.- Although the foliage is damaged or dies during frosts, apparently the underground tissues are not affected unless they are frozen. Smallanthus sonchifolius is known to tolerate temperatures as low as 4º C. Provided that the tubers are not damaged, the plant can shoot again in spring. It needs near 200 days of no-frost climate before the tubers are ready for harvest.

In New Zealand, the stems have been reported to be destroyed at -3º C or -4º C, and a temperature of -7º C during several hours damaged the underground organs. Besides, temperatures less than 10º C to 12 ºC combined with high solar radiation lead to a foliar damage (Grau, 1993).

The optimal development is reached within 18º C and 25º C. The foliage can tolerate temperatures relatively high, at least 40º C, without any symptom of damage, provided that a suitable water supply is maintained. Apparently, Smallanthus sonchifolius needs low night temperatures in order to form optimal tuberous roots.

Humidity.- The mature plants possess a well developed foliage, with a high transpiration capacity, so that they require a regular and important water supply. Smallanthus sonchifolius grows better in soils slightly retentive of humidity, with regular watering. In Bolivia, 800 mm of rainfall are considered optimal for its well development. Its storage tubers allow this plant species to overcome periods of drought.

On the other hand, excess of water can provoke the cracking of the root bark, which would produce a reduction in the commercial value and might promote root putrefaction during storage.

Soil.- Although Smallanthus sonchifolius develops well within a wide range of soil conditions; its development is favored by deep, well tilled soils, rich or moderately rich in organic matter and well drained. The latter ones are the best conditions in order to produce edible roots. In heavy soils, the growing is poor. Pretty good harvests have been obtained in sandy terraces on the shores of rivers in Tarija, in Bolivia, and lateritic soils corrected with dolomite, in the State of São Paulo, in Brazil. Smallanthus sonchifolius can tolerate a wide range of pH, from acid to slightly alkaline.

· Propagation.- The cultivated Smallanthus sonchifolius rarely is propagated by seeds. Instead, this plant species is propagated by plantlets or shoots ranging from 8 cm to 12 cm in length, taken from the bottom of the plant stem –it is, at the base of the aerial part of the main stem– with some few cylindrical roots adhered to the shoots. This plant species can also be propagated by the division of the underground rhizomatous stems, which are easy to be parted. Pieces of stem with at least one knot root easily, provided that they are protected from desiccation. The storage tubers do not have the ability to shoot. On the other hand, micropropagation by means of plant tissue culture in vitro is very easy for this plant species.

Contrarily to many other Andean tuber root crops, a survey in Smallanthus sonchifolius has shown that the tubers of this plant species are free of several virus common to tubers, including the potato leaf-rolling virus, and potato virus X, Y, S, M and A (J. Martineau).

Smallanthus sonchifolius can be planted all the year, provided that enough soil humidity and environmental warmness is present. The hilling around the plants is done only once. The initial growing is very quickly, and requires very little attention other than weeding.

· Harvest and Post-Harvest Handling.- This plant species reaches maturity within 6 to 7 months in the lowlands and 1 year in the highlands, such as valley headers. After flowering, the aerial part of the plant withers and dies, thus entering the plant a resting period during the dry season. This period is suitable in order to harvest the tubers.

In regions where frosts are not probable, the tubers can be unearthed without disturbing the plant, which will continue developing and producing more tubers. In regions where frosts are probable, the tubers can be harvested after the plant has died by digging the soil around it; if the taproot is not disturbed, the plant will shoot again in spring and will produce more tubers.

The fragile tubers have to be unearthed carefully in order to avoid damages, since they can break easily. The tubers are to be separated from the main stem, which could be used as fodder for cattle. Yields of 37 metric tons per hectare (Kay, 1973) and even 40 have been reported for intensive cultivation. Smallanthus sonchifolius produces more than 10 kg of tuber roots per plant.

After removing the excess of earth on the tubers, these can be stored for several months in dry and dark places. The unspoiled tubers –it is, the intact ones– conserve well. It is known, for example, that during Spanish Colony times in Peru, Smallanthus sonchifolius was used as food for sailors in open sea. This implies that, unlike cultivators of sugar beet, the producers of Smallanthus sonchifolius could extend the lapse between harvest and the crop processing. Storage turns the roots sweeter because of the transformation of the sugars present in it. The sunlight accelerates this process.

· Yield.- Based on a study performed in Ecuador on 10 clones of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, during a one-year productive cycle, the following yields were obtained:

Raw root: 41 MT/Ha.

Peeled root: 34 MT/Ha.

The dry-matter content of the roots is among 15% and 30% on a fresh weight basis.

7. Yacon Bibliography and References

1. Asami, T., M. Kubota, K. Minamisawa y T. Tsukihashi. (1989). Chemical Composition of Yacon, a New Root Crop from the Andean Highlands. Jpn. J. Soil Sci. Plant Nutr. 60:122-126.
2. Asami, T., K. Minamisawa, T. Tsuchiya, K. Kano, I. Hori, T. Ohyama, M. Kubota y T. Tsukihashi. (1991). Fluctuations of Oligofructan Contents in Tubers of Yacon (Polymnia sonchifolia) During Growth and Storage. Jpn. J. Soil Sci. Plant Nutr. 62:621-627.
3. Aybar, M. J.; Riera, A. N. S.; Grau, A.; Sanchez, S. S. (2001) Hypoglycemic effect of the water extract of Smallantus sonchifolius (Yacon) leaves in normal and diabetic rats. J. Ethnopharmacol., v.74, p.125-132.
4. Bredemann, G. (1948) Über Polymnia sonchifolia Poepp. & Endl. (P. edulis Wedd.) die Yacon-Erdbirne. Bot. Oecon. 1(2): 65-85
5. Cárdenas, M. (1950) Plantas Alimenticias Nativas de los Andes de Bolivia. Folia Univ. (Publ. Univ. Cochabamba) 2, 3 y 4.
6. Cárdenas, M. (1969). Manual de Plantas Económicas de Bolivia. Editorial Los Amigos del Libro. Cochabamba, Bolivia.
7. Castillo, R., C. Nieto y E. Peralta. (1988). El Germoplasma de Cultivos Andinos en Ecuador. VI Congreso Latinoamericano de Cultivos Andinos. Memorias INIAP-Quito, Ecuador.
8. Chaquilla, G. (1997). Obtención de Azúcar a partir de Yacón (Polymnia sonchifolia) y su Potencial. IX Congreso Internacional de Cultivos Andinos. Cusco, Perú.
9. Cobo, Bernabé ((1653) 1890-1895) Historia del Nuevo Mundo. Ed. Marcos Jiménez de la Espada. 4 vol. Sociedad de Bibliófilos Andaluces, Sevilla.
10. Fukai, K., S. Ohno, K. Goto y Y. Hara. (1995). Seasonal Growth and Fluctuations of Sugar Content in Yacon (Polymnia sonchifolia) During Growth and Dormancy. Jpn. J. Soil Sci. Plant Nutr. 66:233-237.
11. Fukai, K., S. Ohno, et al. (1997). Seasonal fluctuations in fructan content and related enzyme activities in Yacon (Polymnia sonchifolia). Soil Science and Plant Nutrition 43(1): 171-177. Food Res. Lab., Mitsui Norin Co. Ltd., Fujieda 426-01, Japan
12. Gonçalez, E., J. D. Felicio, M. M. Pinto, M. H. Rossi, C. Medina, M. J. B. Fernandes, e I.C. Simoni (2003) Inhibition of Aflatoxin Production by Polymnia sonchifolia and its in Vitro Cytotoxicity. Arq. Inst. Biol., São Paulo, v.70, n.2, p.159-163, abr./jun.
13. Goto, K., K. Fukai, J. Hikida, F. Nanjo y Y. Hara. (1995). Isolation and Structural Analysis of Oligosaccharides from Yacon (Polymnia sonchifolia). Biosci., Biotechnol. Biochem. 59:2346-2347.
14. Grau, A. (1993). Yacon: A Highly Productive Root Crop. New Plants Dossier No. 9 Crop & Food Research Institute Internal Report, Biodiversity Programme, Invermay, New Zealand.
15. Hermann, M. y J. Heller, editores. (1997). Andean Roots and Tubers: Ahipa, Arracacha, Maca and Yacon. Promoting the Conservation and Use of Underutilized and Neglected Crops. 21. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Roma, Italia.
16. Herrera, F. L. (1943) Plantas Alimenticias y Condimenticias Indígenas del Departamento del Cuzco. Bol. Dirección Gen. Agric. Perú 14: 48-51.
17. Inoue, A.; Tamogami, S.; Kato, H.; N Akazato, Y.; Akiyama, M,; Kodama, O.; Akatsuka, T.; Hashidoko, Y. (1995) Antifungical melampolides from leaf extracts of Smallanthus sonchifolius. Phytochemistry, v.39, p. 845-848.
18. Kakihara, T. S., F. L. A. Câmara, S. M. C. Vilhena y L. Riera. (1996). Cultivo e Industrilização de Yacon: Uma Experiência Brasileira. Resumos I Congresso Latino Americano de Raízes Tropicais. CERAT-UNESP, São Pedro, Brasil.
19. Leon, J. (1964). Plantas Alimenticias Andinas. Boletín Técnico No. 6 IICA, Lima, Perú.
20. Lipp, F. J. (1971) Ethnobotany of the Chinantec Indians, Oaxaca, Mexico. Econ. Bot. 25(3): 234-244.
21. Lizárraga, L., R. Ortega, W. Vargas y A. Vidal. (1997). Cultivo del Yacón (Polymnia sonchifolia). Pp. 65-7 en Resumenes Curso Pre Congreso - IX Congreso Internacional de Cultivos Andinos. Cusco, Peru.
22. National Research Council. (1989). Lost crops of the Incas. Little known plants of the Andes with promise for worldwide cultivation. Washington, DC, National Academy Press.
23. O´Neal, L. M. y T. W. Whitaker. (1947) Embroideries of the Early Nazca Period and the Crops Depicted on Them. Southw. J. Anthropol. 3(4): 294-321.
24. Ohyama, T., O. Ito, S. Yasuyoshi, T. Ikarashi, K. Minamisawa, M. Kubota, T. Tsukihashi and T. Asami. (1990). Composition of Storage Carbohydrate in Tubers of Yacon (Polymnia sonchifolia). Soil Sci. Plant Nutr. 36:167-171.
25. Pérez Arbeláez, E. (1956) Plantas Útiles de Colombia, 3ª Ed. Librería Colombiana, Camacho Roldán, Bogotá.
26. Pinto, M.M.; Gonçalez, E.; Rossi, M.H.; Felicio, J.D.; Medina,C.S.; Fernandes, M.J.B.; S Imoni, I.C. Activity of the aqueous extract from Polymnia sonchifolia leaves on growth and production of aflatoxin B1 by Aspergillus flavus. Braz. J. Microbiol., v.32, p.127-129, 2001.
27. Rea, J. (1994). Andean Roots. En Neglected Crops: 1492 from a Different Perspective. J.E. Hernándo Bermejo y J. León (editores) Plant Production and Protection Series No. 26. FAO, Roma, Italia. p. 165–179.
28. Safford, N. E. (1917) Food Plants and Textiles of Ancient America. Proc. Int. Congr. Amer. 19: 12-30.
29. Seminario, J. (1995). Descriptores Básicos para la Caracterización de Chago (Mirabilis expansa), Llacón (Smallanthus sonchifolius) y Achira (Canna edulis). I Congreso Peruano de cultivos Andinos, Huamanga, Ayacucho.
30. Uphof, J. C. Th. (1968) Dictionary of Economic Plants, 2nd Ed. Verlag von J. Cramer, Nueva York.
31. Volpato, G. T., F. L. Vieira, F. C. G. Almeida, F. Câmara y I. P. Lemonica. (1997). Study of the Hypoglycemic Effects. of Polymmia sonchifolia Leaf Extracts in Rats. II. World Congress on Medicinal and Aromatic Plants for Human Welfare. Mendoza, Argentina.
32. Weberbauer, A. (1945) El Mundo Vegetal de los Andes Peruanos. Ministerio de Agricultura, Lima, Perú.
33. Weddell, H.A. (1857). Notice sur l’ahipa et l’aricoma, Plantes Alimentaires du Haut-Pérou. Ann. Sci. Nat. Bot. IV. 7:114.
34. Wells, James R. (1965) A Taxonomic Study of Polymnia (Compositae). Brittonia 17: 144-159.
35. Yacovleff, E. (1933). La Jiquima, Raíz Comestible Extinguida en el Perú. Rev. del Museo Nacional (Lima) 3:376-406.
36. Zardini, Elsa. (1991). Ethnobotanical notes on "yacon," Polymnia sonchifolia (Asteraceae). Economic Botany 45(1): 72-85.