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Y a c o n
Y a c o n
Smallanthus sonchifolius
(Poepp. & Endl.) H. Robinson
Alfredo Grau
Laboratorio de Investigaciones Ecológicas de las Yungas
(LIEY)
Universidad Nacional de Tucumán
Yerba Buena, Tucumán, Argentina
and
Julio Rea
La Paz, Bolivia
Y a c o n 200
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson
Contents
1
Introduction
2
Vernacular names
3
Taxonomy
3.1 The genus
3.2 The species
3.3 The other Smallanthus species
3.4 Relationships between species
4
Species description
4.1 Botanical/morphological description
4.2 Reproductive biology
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
10.1 Photoperiod
10.2 Temperature requirements
10.3 Water requirements
10.4 Soil requirements
11 Agronomy
11.1 Propagation
11.2 Crop husbandry
11.3 Pests and diseases
11.4 Harvesting and post-harvest handling
11.5 Yields
12 Limitations
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236 Promoting the conservation and use of underutilized and neglected crops. 21.
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13 Prospects
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13.1 Advantages of yacon
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13.2 Development objectives
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14 Research needs
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References
239 202
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson
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. Promoting the conservation and use of underutilized and neglected crops. 21.
203
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. Robinsons 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. Promoting the conservation and use of underutilized and neglected crops. 21.
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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 an