Tropaeolum tuberosum / Knolcapucien / Mashwa

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 1 000 m², it is difficult to ascertain its cultivated area and production. However, it is estimated that around 6 000 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 lncas, 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.

Uses and nutritional value
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.

Botanical description
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.

Ecology and phytogeography
Mashwa is cultivated from Colombia to Bolivia, from 3 000 to 4 000 m, with a greater concentration between 3 500 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.

Genetic diversity
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 tetraploid (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.

Mashwa collections in South America
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.

Cultivation practices
Mashwa cultivation practices are the same as those described for the oca.

Prospects for improvement
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 tend would seem to be a limiting factor not only in Cuzco but also in other parts of the Andes. Low crop yields would not he a serious limiting actor, since the mashwa responds well to good soil management. Seed scarcity is a problem that can he solved.

The main lines of research are as follows:
· the function of undesirable substances: 
· the long cultivation period:
· tuber storage;
· the selection of varieties for the various agro-ecological conditions;
· consumption patterns in rural and urban populations.
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