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 cultivated in parts of the Andes for its edible tubers.

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 from 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.
This plant is one of the S. American species of potatoes. It can probably be grown in much the same way as potatoes are grown by planting out the tubers in spring and harvesting in the autumn[].
The plant takes 150 - 195 days from planting out the tubers to harvesting a crop[].
The plant has a shallow root system[].
Yields are quite low[]. Plants might have strict daylength requirements and may yield poorly in temperate zones because they need short-days in order to induce tuber-formation[].
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 early spring in a warm greenhouse. 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 after the last expected frosts.
Division. Harvest the tubers in autumn after the top-growth has been cut back by frost. Store the tubers in a cool frost-free place overwinter and replant in mid spring.