Solanum tuberosum L.

Solanaceae, Jennifer M Edmonds. Oliganthes, Melongena & Monodolichopus, Maria S. Vorontsova & Sandra Knapp. Flora of Tropical East Africa. 2012

Type

Type: ? Cult in Europe, “Habitat in Peru”, Herb. Linnaeus 248.12 (LINN!, lecto, designated by Hawkes in Proc. Linn. Soc. London 166: 106 (1956)) [see also Knapp & Jarvis in J.L.S. 104: 358, f. 25 (1990) & Jarvis, Order out of Chaos: 862 (2007)]

General

Perennial herb, procumbent, creeping or sprawling to 1 m in height with long tuberiferous stolons; tubers extremely variable in colour and shape, small to large; branches spreading or ascending, often flexuous, stems angular or winged, pilose with simple, appressed, eglandular occasionally glandular hairs

Leaves

Leaves alternate, imparipinnate, 8–28 × 6.5–16 cm, rachides 6–10 cm long, with 3–5 alternate or opposite primary leaflets, ovate to lanceolate and decreasing in size towards the base, 3–6(–10) × 2–4(–7) cm, bases cuneate, entire, apices acute, often oblique, terminal often larger and sessile, usually alternating with small sessile interstitial leaflets 0.4–3 × 0.3–2 mm; surfaces pilose with eglandular hairs, denser below; petioles (and rhachides) often angular or narrowly winged, 2–4(–12) cm long, petiolules absent to 2 mm

Inflorescences

Inflorescences terminal becoming lateral with sympodial growth continued by axillary branches, forked cymose panicles, 7–18(–30)-flowered; peduncles 6–12 cm long; pedicels usually erect in flower and in fruit, 1.6–2 cm long, articulated above the middle; axes pilose/villous with long eglandular hairs, dense around point of pedicel articulation

Calyx

Calyx campanulate/stellate, 6–7 mm long, pilose/villous externally with scattered long eglandular hairs; lobes broadly triangular tapering narrowly above, 3–9 × 2–3 mm, acute

Corolla

Corolla white, blue or violet, often with white radial stripes between the lobes and greenish-yellow basal star, rotate to rotatepentagonal, 1.8–3.5 cm diameter, tube 1.8–2 mm long; lobes broadly triangular, 3–5 × 3–5 mm, tips pubescent, glabrous internally

Stamens

Stamens equal; filaments free for 1–2.2 mm, glabrous; anthers yellow to brown, 4–6.2(–8.5) × 1.1–3 mm

Ovary

Ovary 2.2–4 × 1.8–3.5 mm, glabrous, usually bilocular; style straight, sometimes twisted or sigmoidal, 6.5–13 × 0.2–0.4(–0.8) mm, glabrous above, minutely papillate below, exserted to 3 mm; stigma capitate to clasping, 0.5–1 × 0.5–1.3 mm

Fruits

Fruit green, globose to ovoid berries, 1–2(–4) cm diameter, glabrous and smooth, rarely produced in cultivation

Seeds

Seeds up to 500, ovoid to elliptic-ovoid, ± 2 × 1.7–2.4 mm, flattened, often covered with the remnants of strands of thickening appearing as pseudo-hairs; sclerotic granules absent.

Ecology

Commonly cultivated in gardens and vegetable plots, but rarely collected; 1650–1950 m

Note

The potato is probably the best-known and economically important member of the Solanaceae ranking among the top five of the world’s most important crop species. It is indigenous to the Andes of Peru, Chile, Bolivia and adjacent parts of South America, with Hawkes (1991) suggesting that its cultivation probably originated in northern Bolivia. The potato was introduced to Europe by the Spaniards in the 1570s, and is commonly known as the White, European or Irish potato. Widely cultivated for its edible tubers or potatoes in temperate and tropical mountain regions both throughout Africa and world, it was introduced into East Africa approximately 100 years ago, though West African introductions occurred much later - after the Second World War. Correll (1962), however cited evidence that potatoes were grown in South Africa in 1833; he thought this may have indicated that some representatives of section Tuberarium (Dunal) Bitter occurred naturally in Africa, suggesting that an indigenous species might occur there possibly due to Continental Drift. Jaeger (1985) considered this highly unlikely, stating that no close relatives of section Petota are indigenous in Africa. Despite its widespread use as an important vegetable throughout these regions, very few herbarium specimens of this species have been collected. Though frequently planted, this species is rarely naturalised. References to the vast literature dealing with the origins, distribution, inter-relationships with wild species and the cultivars of this tetraploid species may be found in Correll (1962) and Hawkes & Hjerting (1969), while a summary of the evolution and domestication of the potato is given in Hawkes (1991). Mansfeld (2001) similarly gives relevant references to the two subspecies commonly recognized in this species: subsp. tuberosum and subsp. andigena (Juz. & Buk.) Hawkes together with their differentiating features, origins and probable current distribution ranges. The vegetative parts and immature berries of this species contain high glycoalkaloid contents, resulting in ‘green’ potatoes being commonly regarded as poisonous.

Distribution

Range: Europe, Middle East, India, China, Australia and New Guinea, N, C and S America, sometimes occurring as an escape Range: Cultivated in Ghana, Cameroon, Somalia, Ethiopia, Uganda, Tanzania, Malawi, South Africa Flora districts: K4