Figure 15. Andean tubers: A) oca (Oxalis tuberosa); A1) tuber; B) mashwa (Tropaeolum tuberosum); B1) tuber
The authors of this chapter are C. Arbizu and M. Tapia (CIP. Lima, Peru).
Botanical name: Oxalis tuberosa Molina
Family: Oxalidaceae
Common names. English: oca, oxalis; Quechua: oqa, ok'a; Aymara: apilla; Spanish: oca (Peru, Ecuador), oca, ibia (Colombia), ruba, timbo, quiba (Venezuela), papa roja, papa colorada, papa extranjera (Mexico)
Oxalis tuberosa is a crop native to the Andes. Together with the potato. the domestication of this and other Andean tubers in the central region of Peru (lat. 10°S) and northern Bolivia (lat. 20°S), where the greatest diversity both of cultivated and wild forms is found, is thought to have given rise to agricultural activity in the higher agro-ecological areas of the Andes. The migrations of pre-Columbian communities extended its cultivation to lat. 8°N in Venezuela and lat. 25°S in northern Argentina and Chile. Its cultivation was introduced into Mexico about 200 or 300 years ago and, nowadays, it is grown relatively extensively in the region of the Transverse Neovolcanic Axis. Oca was introduced into Europe in the last century and, even though it was produced as a new vegetable, it did not become established as a permanent crop. It is known to have existed in New Zealand since 1860 and its cultivation seems to have gained popularity in the last 20 years.
The oca is sown together with the ullucu, mashwa and native potatoes on plots from 30 to approximately 1000 m2. It is therefore difficult to tell what its cultivated area and production is. However, it is estimated that 20000 ha are sown annually in Peru, with an average production of 3 to 12 tonnes per hectare, although some experimental selections and treatments have produced as much as 97 tonnes per hectare.
Oca is first sun-dried to make it sweeter and then parboiled, roasted or prepared as pachamanca (meat roasted in a hole in the ground).
The dried, frozen tuber is called khaya. If it is washed after freezing, a whiter product called okhaya is obtained which is considered to be of superior quality. The flour of the latter is used to make porridges and desserts. Oca is first and foremost a good source of energy; its protein and fat content is low.
O. tuberosa is an annual, herbaceous plant that is erect in the first stages of its development, and decumbent or prostrate towards maturity. The tubers are claviform-ellipsoid and cylindrical, with buds on the whole surface, and variegated in colour: white, yellow, red and purple.
The leaves are trifoliate, with petioles of varying length (2 to 9 cm). The inflorescences consist of four or five flowers. The calyx is formed by five pointed, green sepals. The corolla has five purple-striped, yellow petals; ten stamens in two groups of five; and a pistil that is shorter or longer than the stamens. Propagation is almost exclusively by the tubers. The flower structure has an efficient mechanism which facilitates cross-pollination.
Figure 15. Andean tubers: A) oca (Oxalis tuberosa); A1) tuber; B) mashwa (Tropaeolum tuberosum); B1) tuber
Oca is grown from 3000 to 4000 m, from Colombia to Chile. However, the greatest concentration is found between 3500 and 3800 m, in the suni agro-ecological zone (mountain slopes).
Wild species of the genus Oxalis are found on the low ridges of the Peruvian coast, or growing sympatrically with cultivated oca in the Andes and on the edges of forests.
The basic number of chromosomes has been established as x = 11. There are reports of ocas that are close to pentaploid (2n = 2x = 58) and hexaploid (2n = 2x = 66) and also of hexaploid cultivated ocas. The frequency of diploids, triploids, tetraploids, pentaploids and hexaploids as well as those that are not exactly euploid should be clarified. The role of the 2n gametes in the formation of the polyploid complex and the nature of the F1 and F2 material needs to be studied.
The pattern of variability in the oca seems to be fairly complex. In fact, cultivated forms have hitherto been grouped together into a single species which includes several shapes and colours of tuber.
The self-incompatibility system present in the oca and consequent cross-pollination, together with the aesthetic selection made by Andean farmers, must have had an influence on the existence of the wide variety of tuber colours and shapes. as well as the number and depth of "eyes" or "buds".
The wide variability found in the colour of the tubers suggests a continual variation, since colours range from white to black, with various hues of yellow. pink and red in between. Flesh colour also seems to undergo continual variation, although less than skin colour does. Ocas have been seen with ivory-yellow and violet-purple flesh in several hues. There are a great many shapes in the vascular ring pigmented with the same colouring as the skin, followed in colour intensity by the medulla.
Over the past ten years, expeditions have been made to Peru, Ecuador and Bolivia to collect cultivated oca. Field collections in Peru are being maintained and evaluated at the Universities of Cuzco, Huancayo, Ayacucho, Cajamarca and Puno, and at INIAA, where there are over 1000 accessions with sufficient duplications. Most of this material is kept in vitro at the Biotechnological Laboratory of the Universidad Nacional Mayor San Marcos in Lima. The collection of Ecuadorian oca is kept as a field collection at the Santa Catalina station in Quito.
The three Andean tubers (oca, mashwa and ullucu) are grown in the same agro-ecological zone and their soil requirements and cultivation practices are very similar to those of the potato: for this reason they are dealt with together.
In the northern area of the Peruvian sierra. the traditional form of cultivation is on melgas: after cultivation of the potato, the land is divided into three to five plots, each of which is sown with one of the Andean tubers.
On the high plateau of Puno and in the agro-ecological zone of the semi-humid puna, a mixture of tubers is sown. By contrast, in the quechua agro-ecological zone, the oca and ullucu are planted together with maize. These crops show a high response to agricultural work such as fertilization, earthing up, hoeing and, above all, the control of pests and diseases; their production increases to levels of 40 to 50 tonnes per hectare, which are comparable to the highest potato yields.
The prospects for this crop lie in the possibility of increasing its yield and in its use as an alternative source of flour to wheat.
The following aspects should be taken into account:
Botanical name: Tropaeolum tuberosum Ruíz & Pavón
Family: Tropeolaceae
Common names. English: mashwa; Spanish: mashwa, mashua (Peru, Ecuador), isaño, añu (Peru, Bolivia), maswallo, mazuko, mascho (Peru) and cubio (Colombia)
Tropaeolum tuberosum apparently originates from the central Andes (lat. 10° to 20°S). Its cultivation is thought to have been spread by pre-Columbian migrations to Colombia (lat. 8°N) and northern Argentina and Chile (lat. 25°S). In spite of its hardiness, there are no references to its introduction into other countries, possibly because the tuber's flavour is not very pleasant when eaten for the first time.
Grown together with ullucu, oca and native potatoes on plots from approximately 30 to 1000 m2, it is difficult to ascertain its cultivated area and production. However, it is estimated that around 6000 ha are sown annually in Peru, with an average yield of 4 to 12 tonnes per hectare. Under experimental conditions, up to 70 tonnes per hectare have been obtained.
From an agronomic point of view, mashwa is very hardy because it grows on poor soil, without the use of fertilizers and pesticides. Even under these conditions, its yield can be double that of the potato. Its cultivation together with ullucu, oca and native potatoes could be accounted for by the nematicide and insecticide control properties that the plant has.
Since the time of the Incas, who included them in their soldiers' rations, the tubers have had anaphrodisiac properties attributed to them. Today, it is known that testosterone levels are significantly reduced in male rats that are fed mashwa.
Mashwa is important for meeting the food requirements of resource-poor people in marginal rural areas of the high Andes. It is prepared in the form of a stew, as a roast or in the form of thayacha. For the latter preparation, the tubers are exposed overnight to frost and are eaten the following day accompanied by sugar-cane syrup.
T. tuberosum is an annual herbaceous plant of erect growth when it is young and it has prostrate stems with compact foliage when mature. This enables it to compete advantageously with weeds. At first sight, the tubers may be confused with oca tubers, but they can be distinguished by their conical shape, dark markings and a greater concentration of buds on the distal part, as well as by their sour taste.
The growing cycle of this species varies between 220 and 245 days. Unlike oca and ullucu, mashwa produces a great quantity of viable seeds.
Mashwa is cultivated from Colombia to Bolivia, from 3000 to 4000 m, with a greater concentration between 3500 and 3800 m. In spite of the poor-quality soils, extreme temperatures, radiation. variation in precipitation and the winds of the Andes, the plant grows quickly, managing to repel insects and nematodes, suppress weeds and maximize photosynthesis. The proportion of dry matter transferred to the tubers can be as high as 75 percent.
The genus Tropaeolum has a wide geographical distribution and seems to be very variable. There are an estimated 50 species in Mexico and Central and South America. Wild species of mashwa in Peru can be found on the low ridges of the Peruvian coast, on the edges of forests or growing sympatrically with cultivated mashwa in the Andes.
Ornamental Tropaeolum can be found in gardens on the coast and in the Andes. Weed forms of mashwa, called kite añu, are sporadic in the maize or tuber fields of the sierra. T. edule, T. polyphyllum and T. patagonicum have also been described as producers of tubers in the Andes of Chile and Argentina, but they apparently have no economic use.
As in the case of the oca, the crossability groups are not known, in other words the situation of the mashwa's gene stock is unknown.
Chromosome calculations have established the basic number as x = 13. Cultivated forms are clearly tetraploids (2n = 4x = 52). The frequency of diploids, triploids and tetraploids is not known and nor is the possible gene flow.
Cross-pollination and the tendency towards self-fertilization, together with aesthetic selection, must have influenced the appearance of various morphotypes. It can be said that the diversity of the mashwa is less than that of the oca, and slightly less than that of the ullucu. However, variation has been found in tuber colour, shapes, bud characteristics and flesh colour. The tuber's skin colour varies from ivory to very dark-purplish violet, with several hues of yellow, orange and purplish violet in between. Pink or purple speckles or stripes may occur on the skin at the apex and under the buds. Tuberization in the buds is more frequent in clones of shortened conical tubers than elongated and ellipsoid conical tubers. The greatest variation in tuber colours and shapes is found in the region between central Peru and northern Bolivia.
Cultivated mashwa, just like ullucu and oca, has been collected extensively in Peru, Ecuador and Bolivia during the last ten years. The field collections of Peru. stored and evaluated in the gene banks of Ayacucho, Cajamarca, Huancayo, Cuzco and Puno, exceed 300 accessions. Many of the accessions are kept in vitro in the biotechnological laboratory of the Universidad Nacional Mayor San Marcos in Lima. The field collection of Ecuadorian mashwa is stored and evaluated at the Santa Catalina experimental station in Quito.
Mashwa cultivation practices are the same as those described for the oca.
Because of its flavour, the mashwa could have a better chance of more extensive use in animal feeding. In this connection. certain clones with a protein content of up to 11 percent show good prospects.
An investigation into the factors limiting mashwa production. carried out by the CIP in the Peruvian Department of Cuzco (1989). elicited the following answers from the peasants: scarcity of suitable land (28 percent): low crop yields (17 percent): and scarcity of seed (17 percent).
The rise in population and consequent pressure on the land would seem to be a limiting factor not only in Cuzco but also in other parts of the Andes. Low crop yields would not be a serious limiting factor. since the mashwa responds well to good soil management. Seed scarcity is a problem that can be solved.
The main lines of research are as follows:
Botanical names: Solanum x juzepczukii, Solanum x curtilobum
Family: Solanaceae
Common names. English: bitter potato; Aymara: luki; Quechua: ruku; Spanish: choquepito, ococuri
It seems that the domestication of bitter potatoes began some 8000 years ago and that, as cultivated domesticated species, they have been used extensively for at least 3000 years.
Acosta, one of the first Spanish chroniclers to describe the agricultural resources of the Andes, mentions that bitter potatoes that had been exposed to the cold overnight and then pressed and dried were transformed into what was known as chuño and were used as bread is in Europe. A century later, the priest Bernabé Cobo reported that. on the high plateau, there were wild potatoes and bitter potatoes which the Aymaras called aphus and which could only be eaten when processed as chuño: this food constituted the main staple in the high plateau region between Peru and Bolivia.
In spite of their importance for the agro-ecological zones of the puna. where frosts during the growth period limit food production, these crops were not studied during the time of the settlement, nor at the start of the Republic. During the 1920s, the Russian expedition organized by Vavilov and undertaken with his students Juzepczuki and Bukasov made a detailed description of these species on the basis of collections gathered on the high plateau around Lake Titicaca.
Several studies have been carried out on bitter potatoes during the past 50 years, including their origin, description and an evaluation of their nutritional capacity.
The area cultivated at present varies greatly from one year to the next, depending on whether an adequate amount of seed is available. However, there are an estimated 15000 ha in Peru and around 10000 ha on the high plateau of Bolivia, on peasants' plots ranging from 300 to 500 m2 and over more extensive areas on land under sectoral rotation. There are further potential areas for cultivation, the inclusion of which could easily double the current production.
If bitter potatoes are to be eaten, they must first undergo processing to remove the glycoalkaloids. Traditional processes in the upper Andean area. described in various works, consist of exposing the tubers to several night frosts and drying them in strong sunlight at altitudes of 4 000 m to obtain black chuño. Larger bitter potatoes are preferably used to prepare white chuño, also called tunta (Aymara) or moraya (Quechua). Freezing is followed by the peeling, hydrating for up to 30 days and drying.
Black chuño is produced up to the edge of the forest where it keeps very well because of its characteristics as a dehydrated product. White chuño is preferably eaten on feast days. It fetches a high price at town markets where it is an ingredient of various regional dishes. Both white chuño and black chuño are very rich in energy.
The potential of bitter potatoes lies precisely in their ability to withstand low temperatures and yield a surplus. thus constituting an important food reserve. It has been calculated that, between August and March, black chuño can account for 70 percent of the food of rural populations of the Peruvian and Bolivian high plateau.
Solanum x juzepczukii measures 30 to 50 cm and has a semi-rosette growth habit, long, straight leaves. short petioles and a small, blue corolla.
S. x curtilobum is distinguished by its more coriaceous leaves and its corolla, which is bigger and purple with very short lobules and a pointed end.
The tubers vary in size and shape, ranging from rounded (Piñaza) to elliptical, oblong or elongated-oblong (Luki), and in colour. Clones of Ococuri have purple and white tubers.
The growing cycle varies greatly between five and eight months. The clone Piñaza is one of the earliest, taking 150 days; Ruki clones are the latest, taking up to 195 days.
Figure 16. Andean tubers: A) bitter potatoes; A1) tubers; A2) flower; B) ullucu (Ullucus tuberosus); B1) tubers
Bitter potatoes are cultivated at altitudes between 3000 and 4300 m, in the agro-ecological zones of the humid puna and suni, which are characterized by mean growth period temperatures of between 6 and 14°C, with precipitations which vary according to the region and year between 400 and 1400 mm, are spread over five to six months and which coincide with the summer period in the Southern Hemisphere (October-May).
Frosts may occur during the growth stage, with the temperature dropping to -5°C in some years. A greater incidence of low temperatures is observed in the dry period and these affect production heavily, with damage varying according to the species. Recently, in an area of Peru with frosts and temperatures of -5°C, the reduction in the harvest was 5 percent in the case of S. x juzepczukii, 30 percent in the case of S. x curtilobum and 40 percent in the case of the common potato.
The cultivation of bitter potatoes requires soils which have sufficient organic matter (3 to 5 percent) and which have had a period of fallow or adequate rotation. The best yields are obtained on soils which have lain tallow for three to four years and have had 2 to 3 tonnes of manure applied.
Bitter potatoes predominate on land where the main production is livestock and where there is natural pasture and thus little pressure on the land. Because of this, land can be put under a rotational system of crops with canihua (Chenopodium pallidicaule) or fodder plants such as barley or oats. including a prolonged period (up to six years) of fallow during which the natural vegetation covers the soil again. In areas which have a very broken topography and where the puna zone is very close to the suni or quechua (valley) zones, rotation includes other crops suited to these conditions, with tubers such as oca (Oxalis tuberosa) and ullucu (Ullucus tuberosus) or mixtures of these species.
Figure 17. Diagram of chuño processing
In the southern region of Peru and on the Bolivian high plateau, there are a great number of varieties which have been bred by the peasants over centuries and which are suited to various ecological conditions in the highest region of the Andes.
Bitter potatoes belong to two species: S. x juzepczukii triploids and S. x curtilobum pentaploids. Because of their ploidy. which is caused by a high degree of sterility. it is difficult to use the characteristics of bitter potatoes in improvement programmes. The origin of bitter potatoes would seem to be due to various crossings derived from wild species such as S. acaule.
There is greater variability in the species S. x juzepczukii, the main cultivated varieties being Ruki, Luki, Piñaza, Parina, Locka, Parko, Keta and Kaisallu, with white or purple tubers.
In the species S. x curtilobum, we may distinguish those of the Choquepito group and the so-called Ococuri, which are characterized by a lower glycoalkaloid content than S. x juzepczukii.
There is an extensive collection of bitter potatoes in Cuzco and Puno in southern Peru, while a collection from the Bolivian high plateau is maintained at the experimental station of Patacamaya.
Figure 18. The origin of bitter potatoes
The soil is generally prepared with local implements, such as the chakitaklla or foot-plough, with the entire peasant family taking part in the operation. since it involves plots located in isolated places.
The sowing period of bitter potatoes is very much conditioned by the presence of rain, since the cap is grown under rain-fed conditions. The period extends from September to November, depending on whether the rains begin early or late. the tradition being to stagger sowing on two or three dates as a means of reducing the climatic risk. The crop needs to be earthed up once or twice when the plants reach a height of 30 to 30 cm. The start of tuberization coincides with the start of flowering, approximately seven to nine weeks after emergence, and lasts for about four weeks, during which time the absence of humidity and severe frosts is vitally important. In this respect there is a differentiation between early, intermediate and late ecotypes, which may mature between four to six months, hence a wide range is available for improvement programmes.
Fertilization is limited to sheep manure. However, there have been positive responses to the addition of chemical fertilizers in intermediate doses. The var. Piñaza responds better to fertilization than the var. Ruki, but the latter has a higher dry matter content.
The varieties of S. x juzepczukii are better suited to shallow soils than S. x curtilobum, which has deeper roots.
On account of their prostrate habit, bitter potatoes are susceptible to nematodes (Naccobus aberrans), to the Andean weevil (Premnotrypes spp.) and also to wart fungus (Synchytrium endobioticum).
The tolerance of bitter potatoes to low temperatures is considered to be their main advantage and there is considerable scope for making selections from current populations. The existence of several varieties also enables cultivation to be extended to the different soil conditions in the highest area of the Andes. Bitter potato genes have been used more for the improvement of so-called sweet varieties than for their own improvement.
The main limitation is their glycoalkaloid content which gives them a bitter taste. In addition to solanine and chaconine, this includes tomatine, mysine and solamargine. However, since there is wide variability in this characteristic. varieties with a low content of this chemical substance can be selected. Although the current process to remove the bitter taste is fairly suited to local conditions and utilizes the climatic characteristics of the puna effectively, with its severe night frosts and intense daytime solar radiation, it is very labour-intensive (working conditions are very hard): it takes between 14 and 28 days to produce white chuño.
Botanical name: Ullucus tuberosus Loz.
Family: Basellaceae
Common names. English: ullucu, oca quina; Quechua: ulluku, ullus; Aymara: ulluma, illako; Spanish: michurui, michuri, miguri, micuche, ruba, rubia, timbo, tiquiño (Venezuela), chigua, chugua, rubas, hubas, camarones de tierra (Colombia), melloco (Ecuador), olluco, ulluco, lisa, papalisa (Peru), lisa, papalisa (Bolivia) and olloco, ulluca, ulluma (Argentina)
The ullucu is a plant native to the Andes. Ancient in origin, it is likely that its cultivation extended from the Andes of Venezuela (lat. 10°N) to northwestern Argentina and northeastern Chile (lat. 25°S) in pre-Hispanic times. However, the exact region of its domestication is not known. Ceremonial vessels of the Robles Moqo style of the Wari culture (the centre of which was Ayacucho between AD 400 and 700) are decorated with multicoloured representations of Andean plants, including the ullucu. It also appears on qero ceremonial vessels of the post-Incan era. The oldest vestige is the presence of starch among 4000-year-old plant remains from Ancon and Chilca on the Peruvian coast.
The ullucu's wide distribution in the Andes and its age are also revealed in the profusion of regional names.
Of the three Andean tubers, the ullucu is the most popular and has become established on the tables of both the rural and urban population in Ecuador, Peru and Bolivia. Traditional preparations include mellocos soup (Ecuador); olluquito con charqui (ullucu with meat—Peru); chupe (potato, meat, egg and cheese stew) and ají de papalisas (ullucu pepper—Bolivia and Peru). It is also suitable for use in contemporary dishes such as salads. Some varieties contain a greater quantity of mucilage and need to be preboiled before preparation to remove it. The Andean tubers perish easily, which explains why ancient Andean peoples attempted to store surpluses by freezing and drying, processes used also for the ullucu. The product obtained is called lingli in Peru; its average protein content is 1.7 percent in the edible tuber, while the carbohydrate and energy content is slightly less than that of most tubers.
The ullucu is an erect, compact plant which reaches a height of 20 to 50 cm. At the end of its growth it is prostrate. Tuber shapes vary from spherical to cylindrical and colours range from white, yellow, light green, pink and orange to purple. On very rare occasions, it forms fruit; the seed then has the form of an inverted pyramid, with very prominent angles and a corrugated surface.
The origin and development of the ullucu in the cold climates of the Andes suggest that it is one of the crops most suited to the complex agro-ecology of areas between 3000 and 4000 m. Although the precise role of hybridization, introgression and mutation in the ullucu is not known, these must have acted—along with natural and human selection pressure—to favour the plant's distribution and adaptation to the various types of Andean climate and soils.
The wild ullucu would seem to indicate a sympatric distribution with the cultivated ullucu, since up to now it has been found from the Andes of La Libertad in Peru (lat. 8°S) to northwestern Argentina (lat. 25°S). This would appear to indicate a smaller geographical range of habitats than that of the cultivated ullucu. However, collecting expeditions have been orientated towards cultivated material, which is harvested in dry periods when there is no opportunity to collect wild material. It is probable that in the geographical distribution area of the wild ullucu—which seems to be wide—ullucus may be found with interesting characteristics that will help to extend our knowledge of its domestication.
Cultivated ullucus are diploid and triploid, with a basic number of 12. The presence of polyploids in the wild ullucu has also been demonstrated. Nevertheless, the frequency of diploids, triploids and probably tetraploids needs to be determined. In the wild, triploids are generally formed by hybridization between diploids and tetraploids, or by the fusion of a normal gamete and another that has not been reduced between diploid parents. Triploids are generally sterile and the only way of propagating them is vegetatively. Their great vigour allows them to prosper and occur in profusion over a wide distribution area.
The study of meiosis in the cultivated diploid ullucu shows a regular meiotic pairing with the formation of 12 bivalents. Meiosis of the triploids is within expectations, i.e. defective and with the presence of univalents and trivalents. Meiotic pairing of artificial diploid hybrids would need to be researched, provided the combinations are possible.
Cultivated and wild ullucus did not arouse much interest among plant explorers in the past. In spite of the fact that the collections of Bukasov and Juzepczuki in South America between 1925 and 1928 were followed by several expeditions to gather cultivated and wild plants, ullucu does not seem to have been collected, even within the same South American countries. Three stages could be distinguished in the collection of ullucu and the formation of gene banks. The first occurred in the 1920s with the work of Bukasov and Juzepczuki; the second covers the work of León through the establishment of the then greater collection of ullucu germplasm at the IICA, with material from Colombia, Ecuador, Peru and Bolivia. Later, collections of wild ullucus were made in northeastern Argentina and Bolivia by Brucher. The third stage began in the 1970s with small local collections at the Universities of Cuzco, Huancayo and Ayacucho, and likewise in the 1980s. Thanks to very positive help from the IBPGR. FAO, CIID and IICA/OAS they were continued more intensively with national programmes such as those of the IBTA in Bolivia, INIAP in Ecuador and INIAA and the Universities of Puno, Cuzco and Ayacucho in Peru. Under these programmes, gene banks are produced annually. These banks suffer from the following shortages which limit the knowledge and promotion of the ullucu:
Ullucu cultivation practices are the same as those described for the oca.
Although the ullucu is a hardy plant that is suited to the difficult conditions of the Andes, viral diseases seem to constitute one of its most serious problems. Viral infections in gene banks affect up to 80 percent of samples. This is a particularly serious problem, not only for gene banks, but also for the crop's management.
Viruses may form viral complexes of up to four different particles in a single plant, causing loss of vigour, deformation and leaf mottling. Moreover, they are far more difficult to eliminate than bacterial or fungal pathogens. Eradication in commercial varieties and selected genetic material is an urgent requirement, although the number of viruses which affect the ullucu is not known. Studies at the CIP have revealed at least four viruses, but the number may be higher.
Another limiting factor is the prolonged cultivation period. While modem commercial varieties of potato are harvested after four or five months in the Andes, the ullucu takes seven or eight months to mature. In other words, ullucu plants are exposed longer to drought, frost, pests, diseases and other adverse factors which are frequent in the Andes. Productivity in terms of time and space is consequently low. It seems to be one of the causes of marginalization, so that ullucu cultivation is gradually being replaced by varieties of early high-yielding potatoes.
The biggest advantage of the ullucu is that it is firmly established among rural and urban people in areas where its supply is almost continuous throughout the year.