There is no universally accepted treatment for the various species that make up the potatoes. We are following the treatment of Spooner D.M. Et al in 2007 in the 'Proceedings of the National. Academy of Science USA 104: 19398-19403, in which only four distinct genera are maintained - viz; S. Ajanhuiri (diploid forms); S. Curtilobum (pentaploid forms); S. Juzepczukii (triploid forms) and S. Tuberosum, which is subdivided into two cultivar-groups (Andigenum Group of upland Andean genotypes containing diploids, triploids and tetraploids, and the Chilotanum Group of lowland tetraploid Chilean landraces)[].

Common Name: Rucki

General Information

Solanum juzepczukii is a herbaceous, perennial plant forming a low rosette when young but becoming semi-erect as it grows. The stems are 40 - 80cm long from a tuber-bearing rootstock[].
A triploid form of the common potato (Solanum tuberosum). It is sometimes cultivated for its edible tubers in the Andes, mainly as insurance against cold weather[].

Known Hazards

The tubers contain glycoalkaloids and must be cooked or frozen before they can be eaten[].
All Solanum species contain greater or lesser quantities of spirosolane alkaloids, including solanine and solanidine. These are bitter tasting and potentially poisonous when consumed frequently[].

Botanical References

Range

S. America - Bolivia, Peru.

Habitat

Cultivated fields at elevations of 3,700 - 4,100 metres[].

Properties

Edibility Rating
Habit	Perennial
Height	0.60 m
Cultivation Status	Cultivated

Cultivation Details

Solanum juzepczukii is a plant of high elevations in the tropics, usually found at elevations of 3,700 metres or more. It grows best in areas where annual daytime temperatures are within the range 6 - 14°c, but can tolerate 3 - 18°c[]. It is said to be highly frost resistant, and can experience frosts on 300 days of the year[, ]. It prefers a mean annual rainfall in the range 600 - 1,200mm, but tolerates400 - 1,400mm[].
Requires a sunny position. Succeeds in most soils, but grows best in a humus-rich, fertile, medium soil[]. Dislikes wet or heavy clay soils[, ]. Prefers a pH in the range 6 - 7, tolerating 5.5 - 7.5[]. Prefers a slightly acid soil, the tubers are subject to scab on limy soils or those deficient in humus.
The plant takes 150 - 195 days from planting out the tubers to harvesting a crop[].
Yields can be quite low[].
The plant has a shallow root system[].
A triploid species, it does not produce fertile seed[].

Edible Uses

Tubers - cooked[, ]. Rich in starch but with a bitter taste. This bitterness can be removed by freeze-drying the tubers to make a food called 'chuño'[]. This is one of the principle species used in the Andes for the production of 'chuno', a freeze-dried potato product[]. White chuno is made by freezing, peeling, soaking and then sun-drying the potatoes. Black chuno is made by the same process, but without the soaking[]. White chuno is much less bitter than black[]. Chuno is most commonly used in soups and stews, combined with barley and herbs[]. It can be mixed with molasses and fruit to make a sweet dessert known as 'mazamorra'[]. Chuno can be stored for 3 - 4 years[].

Leaves - cooked[].

Medicinal

None known

Other Uses

None known

Propagation

Seed - sow in a nursery seedbed or in containers. Prick out the seedlings into a fairly rich compost as soon as they are large enough to handle and grow them on fast. Plant them out when large enough.
Division. Harvest the tubers when the plant is dormant and replant where required.

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