Table of Contents
Sperling, C.R. and S.R. King. 1990. Andean tuber crops: Worldwide potential.
p. 428-435. In: J. Janick and J.E. Simon (eds.), Advances in new crops.
Timber Press, Portland, OR.
Andean Tuber Crops: Worldwide Potential
Calvin R. Sperling and Steven R. King
- The Andean Crop Complex
- Current Distribution
- AGRICULTURAL REQUIREMENTS
- Environment and Habitat
- Cultural Practices
- Cropping Cycle
- NUTRITIONAL VALUE
- Comparative Nutritional Value
- Secondary Compounds
- International Collections
- Table 1
- Table 2
- Fig. 1
- Fig. 2
- Fig. 3
- Fig. 4
- Fig. 5
- Fig. 6
- Fig. 7
- Fig. 8
- Fig. 9
- Fig. 10
- Fig. 11
The Andean region of South America is one of the eight centers of diversity of
cultivated plants described by Vavilov (1951) and has recently become
recognized as an important area for minor-crop development and germplasm
conservation (IBPGR 1982). There is also strong evidence that the southern
Peruvian Andes is one of the four areas of the world where the independent
invention of agriculture took place (Hawkes 1983).
The potato has been the subject of international crop development and is now
commonly grown throughout the world. There are, however, many other important
food crops that were domesticated in the Andes but that are poorly known
scientifically. The subject of this paper is three of these crops: Ullucus
tuberosus Caldas (Basellaceae, Fig. 1, 2); Oxalis tuberosa Mol.
(Oxalidaceae, Fig. 3, 4); and Tropaeolum tuberosum R. & P.
(Tropaeolaceae, Fig. 5, 6). Each of these crops is a potential new crop for
other areas of the world.
Numerous other root and tuber crops have been domesticated in the Andes;
Arracacia xanthorriza Bancr. (Apiaceae), Canna edulis Ker-Gawl.
(Cannaceae), Lepidium meyenii Walp. (Brassicaceae), Mirabilis
expanse R & P (Nyctaginaceae) and Polymnia sonchifolia Poepp.
& Endl. (Asteraceae). No discussion of Andean crop resources would be
complete without mentioning the global potential of these and other crops that
are part of the agricultural heritage of the Andean region. Other important
crops include the high protein pseudograins, Chenopodium quinoa
Willd. (Chenopodiaceae), C. pallidicaule Heller, and a high protein
legume, Lupinus mutabilis Sweet (Fabaceae). As a group, these tuber,
grain legume and other crops have been among the primary food sources in the
highland Andean region for centuries. A National Academy of Sciences report on
Andean crops has presented general information on these and other crops (NRC
These herbaceous crops are all annually propagated for their starchy tubers.
Tubers are produced below ground on axillary stolons which enlarge to form
terminal tubers. Ullucus tuberosus, ("Ullucu" or "lisas"), produces
smooth spherical tubers 2-10 cm across or curved and elongate to 25 cm long.
Oxalis tuberosus ("Oca") and Tropaeolum tuberosum ("Mashua" or
"Añu") despite being in different botanical families bear many
morphological similarities. Both produce elongate tubers slightly roughened
from the enlarged scale leaves.
Sources for dating the presence and importance of Andean tubers include
illustrations on wooden vessels (keros), ceramic urns, and sculptures. Images
of Oxalis tuberosa and Ullucus tuberosus have been documented on
keros from the early post-conquest era in Southern Peru (Vargas 1981). A
"pacheco" urn dated to 950 (before present) BP from the central Peruvian
highlands is decorated with paintings of all three of these tubers (Yacovleff
and Herrera 1934, Sperling 1987). Botanical material from several coastal
Peruvian archaeological sites has also been identified as containing starch
grains, vessels and xylem elements of all three of the crops discussed in this
paper (Martins 1976). Evidence of Oxalis tuberosa and Ullucus
tuberosus dating to ±4,250-4,050 BP has been recorded in the dry coastal
dessert of Peru (Martins 1976). One highland archaeological site, Tres
Ventanas at 3,925 m has yielded material of Ullucus tuberosus reputed to
be from a time period 10,000 years BP (Engel 1970).
These three crops are cultivated in the Andean region from Venezuela to
Argentina (Fig. 7). Outside of the Andean region Oxalis tuberosa is
cultivated commercially in Mexico and New Zealand (Fig. 8). Compared to
potatoes, which are now cultivated in 130 countries around the world, these
tubers are essentially still unknown outside of the Andean region. The crop
characteristics that have, up to now, caused this limited distribution will be
As with most tuber crops, all three Andean tuber crops discussed here are
propagated vegetatively. Whole tubers are selected from storage for annual
planting. No effort is made to select larger or more vigorous appearing
tubers. In fact, smaller tubers are preferred for planting in Peru as they are
less valuable for food.
As these tuber crops have been vegetatively propagated from thousands of years
there has been little selection pressure for sexual seed production, a common
pattern in most vegetative crops. Seed production is uncommon in two of these
tubers. Ullucus tuberosus and Oxalis tuberosa. Ullucus
tuberosus was long thought to be have been a completely sterile plant.
However, fruit production has recently been independently documented (Rousi et
al. 1986, 1988; Sperling 1987) and germination has been observed for some true
seed (Rousi et al. 1988). True viable seed has only recently been documented
in Oxalis tuberosa (Gibbs et al. 1978) while Tropaeolum tuberosum
is known to occasionally produce fruits with viable seed (J. Rea pers. commun.).
All three tuber crops are adapted to high Andean altitudes of 2,400-4,000 m
(4,200) where introduced Old World crops are not well adapted. The few other
crops found at the upper attitudinal limits of agriculture in the Andes are
bitter potatoes, (Solanum spp.) "maca" (Lepidium meyenii) and
barley. The high altitude Andean ecosystem is typified by steep terrain,
strong winds, shallow soil and bare rock surfaces with high water run-off. Low
minimum temperatures and large ranges in diurnal temperatures impose severe
stress on plants.
Cultural practices for all three tubers are similar to potatoes. Planting is
done in rows or hills 80-100 cm apart with plants spaced 40-60 cm apart in the
rows (Rea 1975). Most planting and harvest is by hand, with mechanization rare
or unknown. Monoculture predominates, but interplanting of several tuber
species in one field is common. In many instances Andean farmers will allow a
mixture containing two or three tuber crops to be planted in one field. Often
this mixture consists of several different clones of each species. Such mixed
fields may later be sorted into tuber types during harvest or before cooking.
Mixed planting with legumes or grain crops is occasionally practiced.
The length of cropping cycle is quite variable from the northern to southern
Andes. In Colombia, planting takes place from March to August followed by
harvest 180-360 days later. In Equador, planting starts in December in some
areas and may continue until July depending on local climate. In Peru, tubers
are most commonly planted in November and harvested in June. Irrigation is
practiced in some areas. The variation in cropping cycle reflects not only the
different climatic and day length regimes of the Andes, but also the variation
between different clones of each species.
All three crops are short day length plants. Ullucus tuberosus requires
11-13.5 hours of day length for stolon formation and tuberization (Razumov
1931; Sperling 1987). Tubers fail to form under longer days. In each species
tubers are borne on axillary stolons produced below, or rarely above ground
which are positively geotropic and enlarge into terminal tubers underground.
Andean farmers report that few pests or diseases bother these crops. However,
viruses can be a problem as in many clonally propagated crops. Ullucus
tuberosus may contain complexes of three or four viruses. These viruses
are identified as a potevirus (PMV/U, a tobamovirus (TMV/U) a polyvirus,
(Ullucus mosaic virus, UMV), and a newly recognized comovirus
(Ullucus virus C) (Brunt et al. 1982b). All four viruses have been
experimentally eliminated from Ullucus tuberosus using meristem-tip
culture and chemotherapy (Stone 1982). Eliminating viruses dramatically
increases plant vigor and yield (Stone 1982). Further research on this topic
is needed. Material exchanged internationally will have to be disease free.
Yields vary with the cultural method but are similar for all three species with
Ullucus tuberosus and Oxalis tuberosa producing about 7-10
tons/hectare. In Peru, Ullucus tuberosus and Oxalis tuberosa are
each planted on 15,000 hectares annually (King 1987). Annual production
figures are difficult to determine as much of the crop is cultivated in small
fields in remote areas.
Nearly all production is for fresh market consumption. Traditional dishes,
especially soups and stews are prepared from all three tubers. Ullucus
tuberosus has a smooth, somewhat mucilaginous taste, similar to okra and
makes excellent soups. Oxalis tuberosa, has a sweet acid flavor. A
very small portion of the Ullucus tuberosus crop is canned and exported
to major cities of the United States (see Fig. 9). One of the important
factors for people within and outside the Andean region is the nutritional
value of the crops.
Nutritional analysis of these tubers has shown that there is great variation in
both the quantity and quality of protein within and between cultivars of the
three species (King and Gershoff 1987). Clearly much variability exists in the
protein content of these species. Recently conducted amino acid profiles of
these three species has revealed that they contain a good balance of essential
amino acids, with the limiting amino acids being valine and tryptophan (King
In Table 1 the mean proximate nutritional value of these three crops and
several other root and tuber crops utilized around the world are compared.
These data show that Ullucus tuberosus compares favorably to
Ipomea batatas (sweet potato), and Manihot esculenta
(cassava) in protein content Oxalis tuberosa is nearly equal to
Solanum tuberosum (potato) and is superior in caloric value to
Dioscorea spp. (true yams). The nutritional value of these Andean tuber
crops then is good when compared with staple root and tuber crops eaten around
Each of the three species has been found to contain low levels of secondary
compounds. Ullucus tuberosus, contains saponin (Hegnauer 1964),
Oxalis tuberosa contains oxalic acid (King 1988) and Tropaeolum
tuberosum contains a mustard oil, p-methoxybenzyl isothiocyanate, which has
been used in Andean ethnomedicine (Johns and Towers 1981). The compound of
concern to human nutrition is oxalic acid. The level of oxalic acid in Andean,
Mexican and New Zealand cultivars of Oxalis tuberosa has been shown to
vary between 1.2 to 51.3 mg/100 gram fresh material (King 1988). Even at the
higher levels the oxalic acid content does not pose a threat to human health
unless a persons diet consisted of 100% Oxalis tuberosa. Potatoes
contain 2-7 mg/100 g fresh weight of oxalic acid and spinach (Spinacia
oleracea) contains 356 to 780 mg/100 g fresh material.
In recent years there have been several germplasm collecting expeditions in
Ecuador, Peru and Bolivia. Germplasm of all three of these species is now
being stored and evaluated in germplasm banks in Ecuador and Peru (Fig. 10).
The current number of accessions for each species is listed in Table 2.
The Ecuadorian germplasm collection is maintained and evaluated at the
Instituto Nacional de Investigaciones Agropecuarias (INIAP), Santa Catalina
research station. The largest number of germplasm accessions is in Peru, with
a total of five ex-situ germplasm banks located in Cajamarca, Huancayo,
Ayacucho, Cuzco and Puno. These five germplasm banks are coordinated through
the Proyecto Investigacion de sistemas Agropecuarias Andinos (PISA). In Peru,
there is also a collection of all three species at the University of San Marcos
laboratory of genetic resources and biotechnology This duplicate collection
from Peruvian germplasm banks is maintained in-vitro. The primary aim of this
group is to eliminate viruses from the three species.
Finnish researchers at the University of Turku have also collected germplasm of
Ullucus tuberosus in Ecuador, Peru and Bolivia which is being used for
research on variation patterns in this species (Rousi et al. 1986). There are
no other known germplasm banks for the two to three cultivars of Oxalis
tuberosa cultivated in Mexico and New Zealand. Mexican farmers, with only
limited genetic diversity available, have expressed interest in testing some of
the numerous cultivars from the Andean zone.
Oxalis tuberosa is the most well represented of the crops, 1205
accessions being maintained in six germplasm banks in Ecuador and Peru (King
1988). The next largest in number of accessions is Ullucus
tuberosus, followed by Tropaeolum tuberosum.
The large number of germplasm accessions of these three species is likely to
contain much duplication. Research on the biochemical differentiation of these
accessions is being developed for application to the large number of accessions
of Oxalis tuberosa (Stegemann et al. 1988).
There is, however, a high degree of intraspecific diversity within all three of
these species and agronomic characterization of these cultivars is being
conducted at germplasm banks in Ecuador and Peru. In addition, The
International Board for Plant Genetic Resources (IBPGR) is currently supporting
a scientist to assist in the efforts to distinguish genotypes and characterize
Traditionally all three crops have been confined to their naive Andean home.
Attempts were made to introduce them into Europe during the early part of the
19th century but these were largely unsuccessful the plants remaining little
more than curiosities. Recently, there has been an effort to select adapted
clones for trial in other regions of the World. These efforts are aimed at
increasing the crop options available to farmers, increasing diversity of food
sources and developing crops for marginal growing regions. Suitable areas
include high altitude regions in low latitudes and oceanic or insular climates
with long cool growing seasons. Possibilities also exist for treating these
tubers as winter crops in mild climates of the southern and northern
hemispheres. The success of introduction efforts will depend partly on careful
selection of germplasm adapted to specific environments. The requirement of
short days for tuber formation may limit potential production areas. The
existing variation of different clones in response to day length gives promise
that new cultivars adapted to long days or day neutral clones might be
selected. Currently, these tubers are under trial in Nepal for growing in the
Himalayas. With limited protection Ullucus tuberosus can produce a crop
of tubers at Turku, Finland.
Production of true seed will be necessary for breeding. Given the occurrence
of occasional fruit production in each of these species the probability of
identifying mechanisms for seed failure is likely Cytological studies of
Ullucus tuberosus indicate that abnormal meiosis resulting in incomplete
microsporocyte formation may account for the rarity of seed formation (Sperling
Additional exploration and germplasm collection should be undertaken,
particularly at the southernmost portion of cultivation where clones adapted to
longer day are more likely to be found. Exploration should occur in Argentina
and Chile as the Andean tuber complex is reported from the island of
Chilöe. In order to investigate seed biology, accessions should be
obtained for each wild progenitor, especially for Ullucus tuberosus
Caldas subsp. aborigineus (Brücher) Sperling (Fig. 11).
The Andean potato was originally adapted to the same environment and had the
same day length requirements as these three tubers. Given the success of the
potato, there is a strong possibility of successfully introducing these three
tubers in new growing regions.
These three Andean tuber crops have been cultivated in the Andean region for
centuries and they continue to be an important food crop in Colombia, Ecuador,
Peru and Bolivia today. They are a good source of nutrition and have strong
aesthetic appeal due to their wide degree of variation in form and color. A
large degree of the diversity of these species has been collected and is
available for research and breeding. One of the species, Oxalis
tuberosa, has spread to Mexico and New Zealand where it is marketed and
consumed in numerous dishes. Another, Ullucus tuberosus, is now canned
in Peru and exported to many major United States cities.
Much research remains to be done. Germplasm with traits to overcome day length
sensitivity needs to be sought through exploration in the southern extremes of
it cultivated range. Wild forms which produce true sexual seed should also be
sought for breeding programs. Simple methods for eliminating viruses need to
be established and viral free material made available to agronomists and
There is great potential for introducing these crops as new crops for other
areas of the world. The increased acceptance of new food products, continually
expanding demands of the United States produce markets and increased
agricultural interest in alternative crops suggests a greater demand and market
for these new crops. Finally, with increased international research attention
the production and use of these crops in their native Andean range could also
be improved, providing much needed food for increasing Andean populations.
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in Ullucus tuberosus (Basellaceae) from Peru and Bolivia. Ann. App.
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a newly recognized comovirus infecting Ullucus tuberosus (Basellaceae).
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Ph.D. Dissertation, City University of New York.
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Table 1. Comparative proximate nutritional values for Andean Oxalis
tuberosa, Tropaeolum tuberosum, Ullucus tuberosus and other major
crops (per 100 g fresh weight edible portion).
zThe data presented for these species are mean values from Colombia, Peru and
Bolivia. Values for other crops are from Woolfe (1987).
|Species ||Protein (g) ||Moisture (%) ||Fat (g) ||Ash (g) ||Crude fiber (g) ||Carbohydrate (g) ||Calories (kcal)|
|Dioscorea spp. (Yam) ||2.2 ||72.0 ||0.2 ||1.0 ||4.1 ||24.2 ||72.0|
|Ipomea batatas (Sweet potato) ||1.4 ||70.2 ||0.4 ||0.8 ||2.5 ||27.4 ||116.0|
|Manihot esculenta (Cassava) ||1.1 ||62.6 ||0.3 ||0.9 ||5.2 ||35.2 ||145.0|
|Oxalis tuberosa (Oca)z ||0.9 ||79.0 ||0.2 ||0.4 ||0.8 ||18.5 ||79.7|
|Solanum tuberosum (Potato) ||2.1 ||78.0 ||0.1 ||1.0 ||2.1 ||18.5 ||80.0|
|Tropaeolum tuberosum (Mashua)z ||1.5 ||87.0 ||0.1 ||0.5 ||0.8 ||9.7 ||45.7|
|Ullucus tuberosus (Ullucu)z ||1.9 ||85.6 ||0.1 ||0.6 ||0.7 ||10.9 ||52.5|
Table 2. Germplasm accessions in Andean gene banks.
zFrom Castillo, et al. 1988.
| ||No. accessions|
|Species ||Ecuadorz ||Peruy|
|Oxalis tuberosa ||135 ||1050|
|Tropaeolum tuberosum ||49 ||233|
|Ullucus tuberosus ||156 ||255|
yFrom Tapia and Mateo, in press.
Fig. 1. Ullucus tuberosus in Tulcan, Ecuador. Plant habit.
Fig. 2. Ullucus tuberosus in Ayacucho, Peru. Variation in tuber
Fig. 3. Oxalis tuberosa with flowers, Chinchero, Peru.
Fig. 4. Tuber variation of Oxalis tuberosa from market in Pasto,
Fig. 5. Commercial field of Tropaeolum tuberosum during harvest
near Tunja, Colombia.
Fig. 6. Tuber variation in Tropaeolum tuberosum in Chinchero,
Fig. 7. Distribution map of the three species in the Andean zone.
Fig. 8. New Zealand Yam, Oxalis tuberosa, for sale in wholesale
market in Auckland, New Zealand.
Fig. 9. Imported Ullucus tuberosus, sold in New York markets and
several other U.S. cites.
Fig. 10. Ex-situ germplasm bank of the three species in Puno, Peru.
Fig. 11. Wild Ullucus tuberosus subsp. aborigineus in
Last update September 4, 1997