''Oxalis tuberosa'' is a

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...

herbaceous plant Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

that overwinters as underground stem

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growin ...

s. These tubers are known as uqa in

Quechua Quechua may refer to: *Quechua people, several indigenous ethnic groups in South America, especially in Peru *Quechuan languages, a Native South American language family spoken primarily in the Andes, derived from a common ancestral language **So ...

, oca in

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

, yam in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

and a number of other

alternative names Alternative or alternate may refer to: Arts, entertainment and media * Alternative (''Kamen Rider''), a character in the Japanese TV series ''Kamen Rider Ryuki'' * ''The Alternative'' (film), a 1978 Australian television film * ''The Alternative ...

. The plant was brought into cultivation in the central and southern

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

for its tubers, which are used as a root vegetable. The plant is not known in the wild, but populations of wild ''

Oxalis ''Oxalis'' ( (American English) or (British English)) is a large genus of flowering plants in the wood-sorrel family Oxalidaceae, comprising over 550 species. The genus occurs throughout most of the world, except for the Polar region, polar are ...

'' species that bear smaller tubers are known from four areas of the central Andean region. Oca was introduced to

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

in 1830 as a competitor to the

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

, and to

as early as 1860. In New Zealand, oca has become a popular table vegetable and is simply called yam or New Zealand yam (although not a true yam). It is available in a range of colours, including yellow, orange, pink, apricot, and the traditional red.

Cultural significance

Grown primarily by

and

Aymara Aymara may refer to: Languages and people * Aymaran languages, the second most widespread Andean language ** Aymara language, the main language within that family ** Central Aymara, the other surviving branch of the Aymara(n) family, which today ...

farmers, oca has been a staple of rural Andean diets for centuries."Oca, Ulluco, and Mashua": http://www.cipotato.org/roots-and-tubers/oca-ulluco-mashua Of all Andean root and tuber crops, oca is currently second only to

in area planted within the Central Andean region. Oca is important to local food security because of its role in

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...

s and its high nutritional content.

Diversity

Andean farmers, including the indigenous

and

Aymara people Aymara may refer to: Languages and people * Aymaran languages, the second most widespread Andean language ** Aymara language, the main language within that family ** Central Aymara, the other surviving branch of the Aymara(n) family, which today ...

, cultivate numerous varieties of oca. Oca diversity may be described with respect to morphological characters, local cultivar names, or

molecular markers A molecular marker is a molecule, sampled from some source, that gives information about its source. For example, DNA is a molecular marker that gives information about the organism from which it was taken. For another example, some proteins can be ...

Morphological characters

Oca morphotypes are distinguished by foliar, floral, fruit, stem, and tuber characteristics, as described in the International Plant Genetic Resources Institute's document on oca descriptors.IPGRI-CIP. 2001. Descriptores de oca. IPGRI, Rome, Italy; CIP, Lima, Peru. The morphological diversity of oca tubers, in particular, is astounding. Tubers range from 25 to 150 mm in length by 25 mm in width; skin and flesh color may be white, cream, yellow, orange, pink, red, and/or purple and distributed in range of patterns.

Local cultivar names

Oca-growing communities often name varieties based primarily on tuber morphology and secondarily on flavor. For example, common names may include ushpa negra (black ash) or puka panti (red ''

Cosmos The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

'' ''peucedanifolius''). Great inconsistency of nomenclature has been reported within and among communities.

Molecular markers

Numerous studies have additionally described oca diversity through molecular approaches to study protein and genetic variation. Molecular markers, such as

allozymes Alloenzymes (or also called allozymes) are variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus. These are opposed to isozymes, which are enzymes that perfo ...

(e.g., del Río, 1999) and inter-simple sequence repeats (e.g., Pissard et al., 2006), show oca diversity to be low relative to other crops, probably because of its vegetative mode of

propagation Propagation can refer to: * Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials * Propaganda, non-objective information used to further an agenda * Reproduction, and other fo ...

. While genetic differentiation corresponds well with folk classification, cluster analyses indicate that folk cultivars are not perfect clones, but rather genetically heterogeneous groupings.

Edibility

Oca is cultivated primarily for its edible stem

, but the leaves and young shoots can be eaten as a green vegetable also. Mature stems can be used similarly to rhubarb. Andean communities have various methods to process and prepare tubers, and in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

oca is eaten raw with salt, lemon, and hot pepper. The flavour is often slightly tangy, but there is a considerable degree of difference in flavors between varieties and some are not acidic at all. Texture ranges from crunchy (like a carrot) when raw or undercooked, to starchy or mealy when fully cooked.

Use categories

Oca is fairly high in

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl ...

s, concentrated in the skin. Significant variation in oxalate concentration exists among varieties, and this variation distinguishes two oca use-categories recognized by Andean farmers. One use-category, sour oca, contains cultivars with high levels of oxalic acid. Farmers process these tubers to form a usable storage product, called ''khaya'' in Quechua. To prepare khaya, tubers are first soaked in water for approximately one month. Then they are left outside during hot, sunny days and cold, freezing nights until they become completely dehydrated. This process is similar to the preparation of '' chuñu'' from bitter potatoes. Cultivars in this use category are referred to in Quechua as ''khaya'' (name of the dried, processed product) or ''p'usqu'' (sour/fermented), and in

as ''luk’i''. The other use-category, sweet oca, contains cultivars with lower levels of oxalic acid. The traditional Andean preparation methods for this use-category are also geared towards reducing the oxalate level of the harvested vegetable, but without dehydration. This is done by exposure to sunlight, which decreases the organic acid content and thereby increases the sweet taste of the oca. Once exposed to sunlight, oca can be boiled, baked or fried. In the Andes it is used in stews and soups, served like potatoes, or can be served as a sweet. Cultivars in this category are referred to in Quechua as ''wayk'u'' (boiling), ''misk'i'' (sweet/delicious) and in Aymara as ''q'ini''. Sour oca and sweet oca form distinct genetic clusters based on AFLP data. This suggests the possibility of distinct evolutionary histories for each use-category.

Nutrition

Oca is a source of

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

dietary minerals In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...

, and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

.Hermann, M., & Erazo, C. (2000). Compositional changes of oca tubers following post-harvest exposure to sunlight. CIP Program Report, 391–396. Cultivars vary substantially in nutritional content.

Cultivation

Oca is one of the important staple crops of the Andean highlands, due to its easy propagation, and tolerance for poor soil, high altitude and harsh climates.

Distribution

Oca is planted in the Andean region from

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

, from 2800 to 4100 meters above sea level. Its highest abundance and greatest diversity are in central

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

and northern

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

, the probable area of its domestication.Arbizu, C., and Tapia, M. 1992. Tubérculos andinos. In Cultivos marginados: otra perspectiva de 1492. Edited by J.E. Hernández Bermajo and S. León. FAO, Rome, Italy. pp. 147–161.

Climate requirements

Oca needs a long growing season, and is day length dependent, forming tubers when the day length shortens in autumn (around March in the Andes). In addition, oca requires climates with average temperatures of approximately 10 to 12 °C (ranging between 4 and 17 °C) and average precipitation of 700 to 885 millimeters per year. Oca requires short days in order to form tubers. Outside the tropics, it will not begin to form tubers until approximately the autumn equinox. If frosts occur too soon after the autumn equinox, the plant will die before tubers are produced.

Soil requirements

Oca grows with very low production inputs, generally on plots of marginal soil quality, and tolerates acidities between about pH 5.3 and 7.8. In traditional Andean cropping systems, it is often planted after

and therefore benefits from persisting nutrients applied to, or left over from, the potato crop.

Propagation

Oca is usually propagated vegetatively by planting whole tubers. Propagation by seed is possible but is rarely used in practice. Sexual propagation is complicated by several factors. First, like many other species in the genus ''Oxalis'', oca flowers exhibit tristylous

heterostyly Heterostyly is a unique form of polymorphism and herkogamy in flowers. In a heterostylous species, two or three morphological types of flowers, termed "morphs", exist in the population. On each individual plant, all flowers share the same morph ...

and are consequently subject to auto-incompatibility. Furthermore, on the rare occasion that oca plants do produce fruit, their loculicidal capsules dehisce spontaneously, making it difficult to harvest seed. Oca flowers are pollinated by insects (e.g., genera ''Apis'', ''

Megachile The genus ''Megachile'' is a cosmopolitan group of solitary bees, often called leafcutter bees or leafcutting bees; it also includes the called resin bees and mortar bees. While other genera within the family Megachilidae may chew leaves or pet ...

'', and ''

Bombus A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...

'').

Cropping factors

Oca tuber-seeds are planted in the Andes in August or September and harvested from April to June. The first flowers bloom around three to four months after planting, and the tubers also begin to form then. Between planting and harvesting, the oca crop requires little tending, except for a couple of weedings and hillings. Oca is a component of traditional

s and is usually planted in a field directly after the

harvest. A common sequence in this rotation system may be one year of

, one year of oca, one year of

oats The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for human co ...

or faba beans, and two to four years fallow. Within this system, q’allpa is a

term that signifies soil previously cultivated and prepared for planting of a new crop. The cultural practice is similar to potatoes. Planting is done in rows or hills 80–100 cm apart, with plants spaced 40–60 cm apart in the rows. Monoculture predominates, but interplanting with several other tuber species, including

mashua ''Tropaeolum tuberosum'' (mashua, see below for other names) is a species of flowering plant in the family Tropaeolaceae, grown in the Andes, particularly in Peru and Bolivia, and to a lesser extent in Ecuador as well as in some areas of Colombi ...

and olluco, in one field is common in Andean production. Often this intercoppng consists of several different varieties of each species. Such mixed fields may later be sorted into tuber types during harvest or before cooking.

Harmine Harmine is a beta-carboline and a harmala alkaloid. It occurs in a number of different plants, most notably the Syrian rue and ''Banisteriopsis caapi''. Harmine reversibly inhibits monoamine oxidase A (MAO-A), an enzyme which breaks down monoamin ...

found in root secretions of ''O. tuberosa'' has been found to have insecticidal properties.

Yields

Yields vary with the cultural method. Annals from Andean countries report about 7-10 tonnes per hectare for ''O. tuberosa'' production. But with adequate inputs and virus free propagation material, oca production can range from 35 to 55 tonnes per hectare.

Limitations

Pests and diseases limit the production of oca. Crops in the Andes are often infected with viruses, causing chronic yield depression. Adequate techniques to remove viruses have to be applied before the varieties can be used outside the Andean region. Cultivation is also constrained by the Andean potato weevil (''Premnotrypes spp''), ulluco weevil (''Cylydrorhinus spp''), and oca weevil, the identification of which remains uncertain (possibly ''Adioristidius'', ''Mycrotrypes'', or ''Premnotrypes''). These

weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and herbivorous. Approximately 97,000 species of weevils are known. They belong to several families, ...

s often destroy entire crops. Further notable pests are

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s. As already mentioned, both day-length restrictions and the presence of oxalates can also be considered limiting factors. Scientists work with specific breeding, selection, and virus cleaning programs on these purposes.

Conservation efforts

A number of ongoing

ex situ Svalbard GLOBAL SEED BANK, an ''ex situ'' conservation. ''Ex situ'' conservation literally means, "off-site conservation". It is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat; ...

and

in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...

conservation projects currently focus on the preservation of ''O. tuberosa'' diversity. The International Potato Center (CIP) in Peru has several hundred accessions of oca collected from regions in Bolivia, Argentina and Peru to help ensure and maintain diversity. Currently, there are further efforts to collect accession of oca in regions where habitat destruction and pests are threatening diversity of wild oca accessions.

Alternative names

* Apilla in

* Apiña in

and

* Batata-baroa or mandioquinha (literally, "little

mandioca ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated ...

") in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, a name shared with the unrelated arracacha * Cuiba or quiba in

* Hibia or Cubio in

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

* Macachin or miquichi in

* Papa extranjera in

* Huasisai, ''Qua'' or ibi in

, * Truffette acide in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

* Yam in many other places, such as

Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...

and

, where the '' Dioscorea'' vegetables known elsewhere as yams are generally very uncommon.

References

External links

Oca in ''Lost Crops of the Incas''Andean root and tuber crops
at the

International Potato Center The International Potato Center (known as CIP from its Spanish language, Spanish-language name ''Centro Internacional de la Papa'') is a research facility based in Lima, Peru, that seeks to reduce poverty and achieve food security on a sustaine ...

Oca, ulluco, and mashua
at the International Potato Center
''Oxalis tuberosa''
at Plants for a Future {{DEFAULTSORT:Oxalis Tuberosa Root vegetables tuberosa Crops originating from the Americas Crops originating from Bolivia Crops originating from Ecuador Crops originating from Peru Edible plants Perennial vegetables Tubers