Smallanthus sonchifolius: The Superfood of the Andes
Nomenclatural History
Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, also known as yacón, is a plant native to the Andean region of South America. The specific epithet of this plant is believed to be derived from the Latin word for leaf ,“folium”, as S. sonchifolius is known for having a distinct leaf shape. An isotype of the yacón specimen was first published by Poepp. and Endl. in 1842, giving the species the Linnaean binomial name Polymnia sonchifolia. The yacón was first placed under the Polymnia genus and remained in this genus until 1978 when American botanist Harold Robinson noticed morphological differences within specimen found in the Polymnia genus and decided to split the genus into two. These being Polymnia and Smallanthus (Smithsonian Institution, 1978).Despite the fact that this species was only formally documented in the 1800s, it had already had an impact on indigenous peoples for thousands of years prior, as it was noted to be an important part of religious festivals. Yacón was depicted on textiles and ceramic materials which were used during ceremonies, and the first written record of yacón was published in 1615 (Hermann and Heller, 1997). The indigenous name for yacón is derived from the Quechua “yaku” which means “water”. This might be due to the fact that yacón has a high-water content. (Delgado et al., 2013). Other common names include yiquima, jiquimilla, or aricoma, names which are typically observed in other regions of South America. In English the plant is named yacón strawberry because of its sweet flavors (Delgado et al., 2013).
Evolutionary History
Smallanthus sonchifolius is a plant that was officially categorized as belonging to the Asteraceae family in 1933, after many debates about its classification. The Asteraceae family is composed of 2500 species, with over 1600 genera (Rolnik and Olas, 2021). S. sonchifolius was originally classified into the Polymnia genus, which is a genus that also belongs to the Asteraceae family. In 1978, after many morphological differences were found, botanists decided to split up Polymnia into two making a Smallanthus and a Polymnia genus.Smallanthus is typically made up of tall perennial herbs that can reach up to 5ft. Smallanthus is known for plants that have tuberous roots with flowers, that produce sterile seeds thus in order to reproduce, rhizomes must be planted (Vitali and Barreto, 2014). Most of the species found within Smallanthus are native to the Andes region however, a few smallanthus species have successfully been transplanted to Europe, New Zealand, and North America.
In terms of the evolutionary origin of S. sonchifolius, no clear ancestors have been found for this plant (Hermann and Heller, 1997). However, it is hypothesized that yacón arose through the hybridization of two or more Smallanthus species that occupied the same area (Hermann and Heller, 1997). Still, much uncertainty surrounds this plant’s origin due to the fact that analysis of wild Smallanthus populations have historically been understudied. Therefore, this calls for future research into S. sonchifolius, to focus on the gathering genetic data that would lead to a clear evolutionary origin.
Ecology and Life History
Yacón is a perennial plant that is categorized as belonging to the Asteraceae family. For much of its history the exact climate and ecology that are necessary for the successful cultivation of yacón has been unexplored. In recent years however, yacón has gained a lot of traction worldwide, thus more research on the ideal growing conditions have been observed. The wild species of yacón are believed to have evolved in the humid areas of the eastern Andes mountains. Most notably, the wild tubers are believed to have originated in the area between Bolivia and Peru, an area that has mild temperatures and high rainfall (Hermann and Heller, 1997).Shoots begin to emerge between 30-50 days after planting. Four months after planting occurs, the shoots grow very slowly. Between 6-10 months after planting, the plant enters its reproductive period as the flowers begin to bloom. The blooming of the flowers indicates that the content of carbohydrates in the tuber has reached a maximum, thus during this time frame farmers will begin harvesting the tubers (Silva et al. 2018). A typical harvest can produce between 5-20 tubers, each weighing between 200-500 grams giving an average yield of 5kg per plant (Delgado, 2013).
Present day yacón is known for taking advantage of vegetative gaps as well as having a strong preference for disturbed habitats, as it typically grows along riverbanks, landslides, and roadsides (Hermann and Heller, 1997). The typical elevation observed for yacón cultivation is between 1800-3000m (Delgado et al. 2013). The preferred growing season for yacón is during the rainy season which can extend from December to March. However, successful cultivation has been observed outside of this time frame with constant irrigation (Silva et al. 2018). Yacón possesses temperature plasticity, as it has shown to adapt to harsh Andean temperatures, but prolonged exposure can kill the crop. Despite its ability to adapt to different temperatures optimal growth is observed at a range between 18-25ºC. (Hermann and Heller, 1997). Additionally, yacón has shown to do well in areas of rich, well-drained, and light soils. Heavy soils are not ideal as tuber growth is significantly reduced (Hermann and Heller, 1997).
Cultivation Practices
Historically the yacón plant is cultivated in the Andes region of South America, an area which stretches from Venezuela to Northern Argentina. The largest yacón diversity exists in Perú. The typical elevations for successful cultivation of yacón range between 1800-3000m above sea level, and in temperate and subtropical zones. Traditional ways of growing yacón are limited to the vegetative propagation of rhizomes, since yacón seeds are sterile. Since the 1980s yacón cultivation has been introduced to other regions of the world such as New Zealand and Japan. Czech Republic has also begun mass cultivating this plant in order to export to European countries such as Italy, France and Germany. Major cultivation of yacón for export is done by farmers of the Oxapampa area in Peru. These exports are most popularly sent to Japan which then sells yacón as dried products. Harvesting of yacón includes the process of carefully digging into the ground to create a hole surrounding the tubers, which are then pulled by the central stem. The tubers are pulled off of the central stem, In the Andes region yacón is typically sold in small markets and consumed at great volumes during religious festivals such as All Souls’ Day and the Corpus Christi festival. It is theorized that the yacón plant has been cultivated for thousands of years as records of yacón cultivation have been observed during the Incan empire.Domestication History
Researchers argue that yacón is a semi-domesticated plant since it is able to coexist with many other wild Smallanthus species (Aráoz et al. 2013). Yacón ability to coexist with other wild Smallanthus species is believed to have contributed to its evolutionary history. Domestication of yacón has shown to have increased its ability to store water and produce much larger and wider roots (Aráoz et al. 2013). Domestication has also shown to have an impact of the sweetness of the tubers, which in turn has led to an increase in caloric values sustainable for human consumption (Aráoz et al. 2013). The domestication of yacón is still widely debated, however it is believed to have originated during the Incan empire era (Singh, 2011)Morphological Description of Vegetative Attributes
The root system of yacón consists of fibrous roots and edible tuberous storage roots. The storage roots can be up to 25 cm long and 10 cm wide. There can be up to 20 storage roots on a single plant, and they are adventitious, growing from rhizomes. The bark color of the tuberous roots may be cream, pink, purple, or most commonly brown while the storage tissue can be white, cream, yellow, pink, or purple.Yacón has a height of up to 3 meters and its stem, which becomes hollow when the plant matures, can be cylindrical or angular. The leaves of yacón are arranged oppositely on the stem. Its lower leaves are ovate and hastate and connate or auriculate at the base while its upper leaves are ovate-lanceolate. The upper and lower surfaces of the leaves have dense pubescence of glands and trichomes.
Morphological Description of Reproductive Attributes
Yacón has terminal inflorescences with between one and five axes, each with three capitula. Their color ranges from yellow to orange. The ray florets are pistillate, or female, and are about 12 mm long and 7 mm wide. Each has two or three teeth. The disk flowers are staminate, or male, and are about 7 mm long. The achenes are dark brown, and their size ranges from 3.7 mm to 2.2 mm.The rhizomes are used for asexual reproduction through vegetative propagation. They are a reddish color and are located at the base of the stem.
