«Andean roots and tubers: Ahipa, arracacha, maca and yacon M. Hermann and J. Heller, editors Promoting the conservation and use of underutilized and ...»
4.3 Chromosome numbers 5 Origin, evolution and history 6 Geographical distribution and centres of diversity 7 Properties and uses of the species
7.1 Chemical composition
7.2 Uses 8 Genetic resources
8.1 Genetic variation
8.2 Geographical distribution of important traits
8.3 Importance of wild relatives as a source of diversity
8.4 Institutions holding germplasm 8.4.1 Ecuador 8.4.2 Peru 8.4.3 Bolivia 8.4.4 Argentina 8.4.5 Availability of data on individual accessions
8.5 Gaps in existing collections
8.6 Conservation of the cultivated yacon and its wild relatives 9 Breeding 10 Ecology of the species
10.2 Temperature requirements
10.3 Water requirements
10.4 Soil requirements 11 Agronomy
11.2 Crop husbandry
11.3 Pests and diseases
11.4 Harvesting and post-harvest handling
11.5 Yields 12 Limitations Promoting the conservation and use of underutilized and neglected crops. 21. 201
1 Introduction The Andean region has been the cradle of a surprisingly wide range of edible tubers and roots. Most of them have been used by the Andean inhabitants as food energy, while two - ahipa (Pachyrhizus ahipa) and yacon (Smallanthus sonchifolius) -have been considered ‘fruits’. That perception is particularly strong in the case of yacon, which despite its juiciness and sweet taste, has been recognized as a food of relatively low energy value since early times.
Some medicinal attributes may have increased the attractiveness of yacon to the ancient Andean people. However, its high productivity and other attractive agronomic traits could not counterbalance its low nutritive value. This likely led to diminished interest on the part of the old Andean agronomists, who presumably did not work on yacon as they did on potato (Solanum tuberosum), oca (Oxalis tuberosa) or ulluco (Ullucus tuberosus). Furthermore its reduced nutritive value may have contributed to the disappearance of yacon landraces in ‘many areas at different historical stages, in times of crisis or famine. This process has probably accelerated significantly in the present century, owing to the profound political, social and cultural changes happening in the Andes. In recent decades, improved transport has increased the availability of fruits in the region, which may be competing with yacon in the local markets.
In modern times, the human view of yacon could be radically different from in the past. Certainly, calories are still limited and critical in many regions of the earth and the Andes themselves. In contrast, on a global scale, starch, glucose and fructose are comparatively common commodities, with relatively low prices, and are available to certain sectors of the human population in quantities well above their dietary requirements and even beyond their physiological tolerance. Under these conditions, yacon may provide the low calories and fiber necessary to survive the stress of sedentary lifestyles combined with overconsumption of carbohydrates and fats.
The productivity and other valuable agronomic traits of yacon strongly suggest that it is a species with a great potential. With limited testing and fine tuning, addition of conventional fertilizers to the clones developed by the old Andean agronomists has produced annual yields of up to 100 t/ha (fresh weight). It is easy to speculate on potential yields if modern breeding techniques, hybridization or genetic engineering were applied. But perhaps the challenge of the future will be not only to breed yacon into a very productive multipurpose crop and to satisfy several aspects of modern life requirements, but also to pay back to the descendants of the old Andean agronomists a fair share for their invention.
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2 Vernacular names The species has received common names in the dominant Andean languages, Aymara and Quechua (Cárdenas 1969). Aricoma and aricuma, the Aymara terms, are used in certain areas of Bolivia. Llaqon, llacum, llacuma or yacumpi are the Quechua words that evolved into ‘yacon’, perhaps after the Spanish conquest. In the Quechua language, yacu and unu are words meaning water, while yakku is an adjective meaning watery or insipid. ‘Yacon’, with subtle regional differences in the pronunciation of the ‘y’ and the ‘c’ or ‘k’, is commonly used from Peru to northwestern Argentina.
Much less frequent is the term ipio, used by the Chiriguano groups in the lowlands of Southern Bolivia. In Ecuador, jicama, chicama, shicama, jiquima or jiquimilla are the common names of the species (Tittel 1986). These terms closely resemble and probably derive from xicama, the Mexican term applied to Pachyrhizus erosus and extended to the other members of the genus Pachyrhizus. This word was presumably introduced by the Spanish invaders, who began their Andean conquest in Ecuador after arriving from Central America. The term arboloco, used in Colombia, suggests very strongly a Spanish background. Yacon has also received names in other European languages, coined probably by researchers or growers: poire de terre (French) and yacon strawberry (English).
204 Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson 3 Taxonomy
3.1 The genus Yacon and its relatives were originally placed in Polymnia (Compositae, Heliantheae, subtribe Melampodinae), a genus founded by Linnaeus in 1751. De Candolle (1836) produced the first comprehensive treatment of the group. Later, important contributions were made by Blake (1917, 1930). In the first modern revision of the genus, Wells (1967) maintained yacon and its relatives within Polymnia.
A different perspective was adopted by Robinson in a more recent study (1978).
Robinson re-established the genus Smallanthus, proposed by Mackenzie in 1933.
Robinson separated the species previously considered within Polymnia by Wells into two genera — Smallanthus and Polymnia — keeping both within the subtribe Melampodinae. One North American species, most Central American species and all South American species were placed in Smallanthus, while a few North American species remained in Polymnia. According to Robinson, there are important differences separating Polymnia from Smallanthus (e.g. striation on the cypsela surface, presence of a whorl of outer involucral bracts, absence of glands on the anther appendages, lack of a particular feature in the lobes of the disk flower corollas).
Some of those characters place Polymnia as the most isolated genus within the subtribe, while Smallanthus is closer to other genera in the group, such as Melampodium and Espeletia, than to true Polymnia. Robinson’s point of view is formally sound, it has gained acceptance by the North American authors and it is being used in the North American herbaria. Smallanthus also has been adopted by Brako and Zarucchi (1993) in their catalogue of plants of Peru, and by Jørgensen and León (1997) in their catalogue of vascular plants of Ecuador.
It is important to point out that both Wells and Robinson principally, or perhaps only, studied herbarium specimens of the South American species. Moreover, herbarium material of these species is scarce, frequently poorly preserved and rarely includes underground organs, which in this case would be of particular interest.
These limitations have certainly affected the work of Wells and Robinson. This fact may explain why Wells’ key to the species is of limited value for identifying the South American taxa.
Smallanthus sensu Robinson includes at least 21 species, all American, ranging mostly through southern Mexico and Central America and the Andes. They are perennial herbs, less frequently shrubs or small trees and only rarely annuals.
3.2 The species Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, Phytologia 39:51. 1978.
Synonyms: Polymnia sonchifolia Poepp. & Endl. Nov. Gen. Sp. Pl. 3:47. 1845.
Polymnia edulis Wedd., Ann. Sci. Nat. Bot. IV. 7:114:1857.
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3.3 The other Smallanthus species Smallanthus apus (Blake) H. Robinson This is a poorly known Mexican species.
Smallanthus connatus (Spreng.) H. Robinson An annual herb up to 2 m tall, widely distributed, present in southeastern Brazil, Paraguay, Uruguay and eastern Argentina to 35°S. It is the southernmost species, closely related to S. macroscyphus.
Smallanthus fruticosus (Benth.) H. Robinson It is a shrub or tree to 12 m tall, distributed in southern Colombia, Ecuador and northern Peru.
Smallanthus glabratus (DC.) H. Robinson A shrub or tree up to 8 m tall, closely related to S. fruticosus and placed by Wells together with S. parviceps and S. microcephalus within the glabrata complex. Its main area of distribution is the Peruvian mountains. It also has been reported in Ecuador and Chile.
Smallanthus jelksii (Hieron.) H. Robinson A shrub or tree up to 8 m tall, described only for Peru, related to S. pyramidalis, both with characteristic small flower heads.
Smallanthus latisquamus (Blake) H. Robinson Considered a synonym of S. quichensis by Wells (1965), S. latisquamus is treated as a separate species by Robinson (1978). Stems up to 3 m tall, present in Costa Rica.
Smallanthus lundellii H. Robinson This species proposed by Robinson (1978) is a herb up to 1 m tall, related to S. latisquamus and S. quichensis, found in Guatemala.
Smallanthus macroscyphus (Baker ex. Martius) A. Grau, comb. nov.
A perennial herb up to 3 m tall, present in Bolivia and northwestern Argentina, where it is known as yacon del campo (wild yacon). It has a well-developed root system with storage roots that can reach 2-5 cm diameter. Smallanthus macroscyphus and S. connatus were treated as synonyms by Wells (1965) and Robinson (1978). On the contrary, Cabrera (1978) and Zardini (1991) consider them different species (Fig. la, b).
Smallanthus maculatus (Cav.) H. Robinson A coarse herb up to 5 m tall. Several varieties of the species have been described for Mexico, Guatemala, Honduras, El Salvador, Nicaragua and Costa Rica.
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson Smallanthus macvaughii (Wells) H. Robinson A herbaceous species up to 5 m tall, present in Mexico and related to S. oaxacanus.
Smallanthus meridensis (Steyerm.) H. Robinson A herb with stems up to 3 m tall, distributed in Venezuela and Colombia.
Smallanthus microcephalus (Hieron.) H. Robinson A shrub or small tree up to 8 m tall, found in Ecuador.
Smallanthus oaxacanus (Sch.Bip. ex Klatt) H. Robinson A herb up to 2 m tall, distributed in Mexico, Guatemala and Honduras.
Smallanthus parviceps (Blake) H. Robinson Another shrub or tree up to 8 m tall with stems of 15 cm diameter. It occurs in southern Peru and northern Bolivia.
Smallanthus pyramidalis (Triana) H. Robinson A tree up to 12 m tall and 20 cm diameter at the base, distributed in Venezuela, Colombia and Ecuador.
Smallanthus quichensis (Coult.) H. Robinson Closely related to S. latisquamus and present in the same region, Costa Rica and Guatemala.
Smallanthus riparius (H.B.K.) H. Robinson A herb or shrub up to 4 m tall, with a very wide latitudinal range, from southern Mexico to northern Bolivia.
Fig. 1. Yacon del campo (Smallanthus macroscyphus) growing on a landslide at 1400 m asl in the cloud forest of Tucumán province, Argentina (a); storage root, detail (b).
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Smallanthus siegesbeckius (DC.) H. Robinson Described as an annual herb by Wells (1965). However, observations by Lizárraga and Grau (unpublished) on material responding to the description of S. siegesbeckius indicate that this species is perennial, up to 5 m tall, possessing a well-developed underground system, with many tuberous roots very similar to yacon, 20 cm long and 6 cm diameter or more (Fig. 2a, b). This species has been described for Peru, Bolivia, Brazil and Paraguay. It is possible, however, that the Brazilian and Paraguayan material actually belongs to a different species.
Smallanthus suffruticosus (Baker) H. Robinson A shrub or herb up to 2 m tall adapted to the lowlands of Venezuelan Amazonia.
Smallanthus uvedalius (L.) Mackenzie A perennial herb up to 3 m tall, distributed in the eastern United States of America from New York to Florida and Texas.
3.4 Relationships between species No comprehensive taxonomic study has been carried out beyond Wells’ perspective (1965) and Robinson’s rearrangement (1978). Following, in part, Wells’ guidelines it is possible to distinguish some species groups.
The best-studied group includes the North American-Mexican-Central American species. Owing to the availability of herbarium material this group was thoroughly analyzed by Wells, who recognized several varieties in some of the species. These species are herbs and some of them are related: S. maculatus is hard to distinguish from S. uvedalius; S. macvaughii is close to S. oaxacanus; S. quichensis is related to S. latisquamus and S. lundellii. While geographically distant from yacon, some of the Central American species may be taxonomically close to the ‘yacon Fig. 2. Smallanthus cf. siegesbeckius collected by L. Lizárraga and A. Grau at 1900 m asl, Ahuabamba, Cusco region, Peru: flower (a), underground organs (b).
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson group’ (see below). Smallanthus riparius, the only Central American species that extends to the Andean region, is indeed a member of that group.
Considering geographical distribution, growth habit and morphology of the aerial parts, six species appear to be close to S. sonchifolius, forming a sort of ‘yacon group’: S. connatus, S. macroscyphus, S. riparius, S. meridensis, S. suffruticosus and S. siegesbeckius. Smallanthus riparius is considered very close to S. siegesbeckius by Wells (1965), to the point that he reported intermediate herbarium specimens.
Smallanthus riparius also closely resembles S. macroscyphus. It is likely that at least two of the species in this group have contributed to the yacon genome. It is also possible that at least some of the material present in different germplasm collections as ‘wild yacon’ is actually Smallanthus species of this group, other than S. sonchifolius.