Solanaceae Source

A global taxonomic resource for the nightshade family

Solanum microdontum

Citation author: 
Repert. Spec. Nov. Regni Veg. 10: 535. 1912.
Argentina. [Salta]: Toldos, near Bermejo, 1800 m, Dec 1903, Fiebrig 2498 (holotype, B, destroyed [F photo 2716, G, MO, NY, photo and fragment: F]; lectotype, W, designated by Hawkes and Hjerting, 1969 [Correll neg. 567, F, NY, PTIS, U]); isotypes, GOET [Correll neg. 958, F, LL, NY, PTIS, UC], M [Correll neg. 571, F, LL, MO, NY, PTIS, UC], SI, U [Correll neg. 566, F, LL, NY, UC]).
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M.
Herbs 0.3-1 m tall, erect or decumbent. Stems 4-10 mm in diameter at base of plant, unwinged or with straight to curved wings up to 5 mm wide, often densely covered with simple, short, brownish, and soft non-glandular trichomes and often with longer glandular trichomes, frequently with whitish dots, green to purple or green and purple mottled.
Sympodial structure: 
Sympodial units tri- to plurifoliate, not geminate.
Leaves simple to odd-pinnate, the blades 8-19.5 x 4.5-12.5 cm, green, membranous to chartaceous, densely pubescent adaxially and abaxially, with hairs like those of the stems; lateral leaflet pairs 0-2, greatly subequal and decreasing in size to the leaf base, most distal lateral leaflets 1.6-6.5 x 1-3.2 cm, broadly ovate to broadly elliptic, sometimes nearly orbicular, the apex acute to acuminate, the base regular to oblique, cordate to elliptical, sessile and decurrent or with petiolules up to 8 mm long; terminal leaflet 6.3-19.5 x 2-9 cm, broadly ovate broadly to elliptical, sometimes nearly orbicular, the apex acute to acuminate, the base slightly cordate to truncate to long attenuate, sometimes to the base; interjected leaflets typically absent; petioles 1-4.5 cm long, often densely covered with simple, short, brownish, and soft non-glandular trichomes and often with longer glandular trichomes, frequently with whitish dots. Pseudostipules 5-10 mm long, lunate, with hairs like those of the stem.
Inflorescences 4-10 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 5-18 flowers, with all flowers apparently perfect, the axes often densely pubescent with hairs like those of the stem; peduncle 1.5-6.2 cm long; rachis 3-8 cm long; pedicels 8-17 mm long in flower and fruit, spaced 1-10 mm apart, articulated at about the middle.
Flowers homostylous, 5-merous. Calyx 4.5-7 mm long, the tube 1-2 mm, the lobes 3.5-5 mm long, apiculate to long attenuate, the acumens 1-5 mm long, with hairs like the stem, Corolla 2.2-2.8 cm in diameter, pentagonal to rotate-pentagonal, white (very rarely white tinged with blue), the tube 1-2 mm long, the acumens 2-4 mm long, the corolla edges flat, not folded dorsally, glabrous abaxially, minutely pubescent adaxially. Stamens with the filaments 1-2 mm long; anthers 5-8 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 7-10 x ca. 1 mm, exceeding stamens by 2-4 mm, straight, glabrous; stigma clavate to capitate.
Fruit a globose to slightly ovoid berry, 1.5-2 cm in diameter, green when ripe, glabrous.
Seeds from living specimens ovoid and ca. 2 mm long, whitish to greenish in fresh condition and drying brownish, with a thick covering of “hair-like” lateral walls of the testal cells that make the seeds mucilaginous when wet, green-white throughout; testal cells honeycomb-shaped when lateral walls removed by enzyme digestion.
Chromosome number: 

2n = 3x = 36 voucher: Okada 6154 (BAL) (Hijmans, et al. 2007)
2n = 2x = 24 voucher: Spooner & Clausen 4632 (PTIS) (Hijmans, et al. 2007)


Central Bolivia (Dept. Cochabamba) to northern and western Argentina (Provs. Catamarca, La Rioja, Jujuy, Tucumán and Salta), in narrow humid quebradas, on the banks of streams, under the shade of trees and bushes, at the border of cultivated fields, in dense forests and woods, growing on dead trees or branches, high grassy mountain plains, in forests and woods; (1400) 1600-2900 (3850) m in elevation.

Flowering and fruiting from December to June.

Solanum microdontum is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. On a higher taxonomic level, it is a member of the informally-named Potato Clade, a group of perhaps 200-300 species that also includes the tomato and its wild relatives (Bohs, 2005).


Many populations of S. microdontum are distinguished by simple leaves, but intra- and interpopulational variability encompasses morphotypes with pinnately compound leaves more similar to those of other wild species. This variability has been partitioned into six species, three subspecies, and six varieties, but recent classifications reduced this variability to one species with two subspecies: subspecies microdontum and subspecies gigantophyllum (Hawkes, 1990) or three varieties, variety microdontum, variety metriophyllum Bitter, and variety montepuncoense (Ochoa, 1990). Phenetic analysis of morphological data (Van den Berg and Spooner, 1992) showed these infraspecific taxa to be unwarranted. Variety microdontum and variety metriophyllum are equivalent nomenclaturally to subspecies microdontum and subspecies gigantophyllum, respectively. Variety montepuncoense was distinguished by rotate corollas white tinged with blue and, but is known only from a single locality and otherwise appears to be S. microdontum. Van den Berg and Spooner (1992) synonymized all of these names, except variety montepuncoense which we now synonymize in S. microdontum.

Brücher and Ross (1953) designated four syntypes for S. simplicifolium variety variabile, deposited at GOET. Van den Berg and Spooner (1992) searched GOET unsuccessfully for these specimens, but the original description makes the affiliation of this name clear. The collector designation, EBS, refers to codes of the Erwin Baur Sortiment Genebank in Cologne, Germany. It is possible that these numbers refer to seed collections and no original collections were made in the field or deposited at GOET.


Brücher, H. & H. Ross 1953. Las especies tuberíferas de Solanum del noroeste Argentino.
Lilloa 26: 453-488 + 4 pl.

Hawkes, J.G. & J.P. Hjerting 1969. The potatoes of Argentina, Brazil, Paraguay and Uruguay: a biosystematic study.
Oxford Univ. Press, Oxford, UK.

Okada, K.A. 1981. High frequency of triploids of Solanum microdontum subsp gigantophyllum on the western mountain ranges of Provinces La Rioja and Catamarca, Argentina.
Bull Torrey Bot Club, 108(3): 331-337.

Hawkes, J.G. & J.P. Hjerting 1989. The potatoes of Bolivia: their breeding value and evolutionary relationships.
Oxford University Press, Oxford.

Hawkes, J.G. 1990. The potato: evolution, biodiversity and genetic resources.
Oxford: Belhaven Press.

Van den Berg, R.G. & D.M. Spooner 1992. A reexamination of infraspecific taxa of a wild potato, Solanum microdontum Bitter (Solanum sect. Petota: Solanaceae).
Pl. Syst. Evol. 182:239-252.

Bohs, L. 2005. Major clades in Solanum based on ndhF sequences.
Pp. 27-49 in R. C. Keating, V. C. Hollowell, & T. B. Croat (eds.), A festschrift for William G. D’Arcy: the legacy of a taxonomist. Monographs in Systematic Botany from the Missouri Botanical Garden, Vol. 104. Missouri Botanical Garden Press, St. Louis.

Hijmans, R., T. Gavrilenko, S. Stephenson, J. Bamberg, A. Salas & D.M. Spooner 2007. Geographic and environmental range expansion through polyploidy in wild potatoes (Solanum section Petota).
Global Ecol. Biogeogr. 16: 485-495.

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