Solanaceae Source

A global taxonomic resource for the nightshade family

Solanum chacoense

Citation author: 
Repert. Spec. Nov. Regni Veg. 11: 18. 1912.
Based on and a nomen novum for Solanum guaraniticum Hassl. var. angustisectum Hassl., not S. guaraniticum A. St. Hil.
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M. & A. Clausen
Herbs 0.5-2 m tall, erect. Stems 3.5-10 mm in diameter at base of plant, green to purple or green and purple mottled, unwinged or with wings to 2 mm, glabrous to densely short pubescent; tubers typically borne singly at the end of each stolon.
Sympodial structure: 
Sympodial units tri- to plurifoliate, not geminate.
Leaves odd-pinnate, the blades 10-39 x 6-24 cm, green, membranous to chartaceous, glabrous to densely short-pubescent adaxially and abaxially with hairs like those of the stems; lateral leaflet pairs 4-7, often subequal except for the most proximal 1 or 2 pairs that are greatly reduced in size; most distal lateral leaflets 2.7-9 x 0.9-3.5 cm, narrowly to broadly ovate to elliptic, the apex acute to acuminate, the base typically oblique, rounded to truncate, petiolules 0-5 mm long; terminal leaflet 4.1-9.4 x 0.9-4.3 cm, ovate to elliptic, the apex acute to acuminate, the base truncate to attenuate; interjected leaflets 0-20, sessile to short petiolulate, ovate to orbicular; petioles 1-4 cm, glabrous to densely short pubescent. Pseudostipules 3-20 mm long, pubescent with hairs like those of the stem.
Inflorescences 2-15 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 8-25 flowers, with all flowers apparently perfect, the axes pubescent with hairs like those of the stem; peduncle 2.5-10.5 cm long; pedicels 12-23 mm long in flower and fruit, spaced 1-10 mm apart, articulation extremely variable from the proximal half to the distal third.
Flowers homostylous, 5-merous. Calyx 3-5 mm long, the tube 1-2 mm, the lobes 1-4 mm, acute to long attenuate, the acumens 0.5-2 mm long, with hairs like those of the stem. Corolla 1.6-3.7 cm in diameter, deeply stellate to pentagonal, pure white to creamy yellow-white adaxially and abaxially, the tube 1-2 mm long, the acumens 2-5 mm long, the corolla edges flat, not folded dorsally, glabrous adaxially, minutely puberulent abaxially, especially along the midribs, ciliate at the margins, especially at the tips of the corollas. Stamens with the filaments 1-2 mm long; anthers 5-7 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 8-15 mm x ca. 1 mm, exceeding stamens by 3-6 mm, straight, glabrous; stigma clavate to capitate.
Fruit a globose to slightly ovoid berry, 1.5-2 cm in diameter, green to green with purple streaks when ripe, often with scattered white dots, 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: Van den Berg et al. 603 (PTIS) (Hijmans, et al. 2007)
2n = 2x = 24 voucher: Okada 5341 (BAL) (Hijmans, et al. 2007)


Solanum chacoense is widely distributed from southern Peru (Dept. Puno) to central Argentina (Depts. La Pampa and Buenos Aires), in a wide diversity of habitats, in full sun or in dense shade, in dry or moist areas, among bushes, in scrub or thorn forests or savannas, near the seashore, in moist subtropical forests, on rocky slopes, in cultivated fields, banana plantations, or roadsides, 0-3700 m in elevation. It has also escaped from cultivation outside its native range in the USA and Europe.

Flowering and fruiting specimens have been collected from throughout the year, but few from August-October.

Solanum chacoense is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. Within sect. Petota, Solanum chacoense is a member of a very diverse clade related to the cultivated potato. 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).


Solanum chacoense is one of the most variable and widely-distributed wild potato species. It is most similar morphologically to S. kurtzianum and S. malmeanum. From S. kurtzianum it is distinguished by its non-ciliate leaf margins, its generally greater height of up to 2 m, and the generally obtuse angle of insertion of the first distal pair of lateral leaflets. From S. malmeanum, it can be differentiated by its larger and erect habit, by the acute apex of the terminal leaflet and generally by a larger peduncle. Solanum chacoense also is similar to S. berthaultii but can be distinguished from that species by the absence of type B (long-stalked) glandular trichomes, by its less pubescent leaves, and its consistently white to creamy-white corollas.

Hawkes and Hjerting (1969), Morton (1976), and Hawkes (1990) considered S. muelleri as a subspecies of S. chacoense and distinguished this subspecies by broader lateral leaflets (3 to 4 times as long as broad). Matesevach and Barboza (2005) synonymized subspecies muelleri under S. chacoense but Correll (1962) and Mentz and Oliveira (2004) consider it at the species level as based upon the following characters: stem unwinged, the absence of a rosette of basal leaves, larger lateral leaflets, no presence of interjected leaflets and if present only 0.2 cm, and irregular acumens. Matesevach and Barboza (2005) synonymized it under S. chacoense but considered material only from Argentina.

We examined specimens of S. chacoense along its entire range and found it to be a highly variable species, although easily recognizable on the bases of leaf and flower morphology. Considering the characters listed by Mentz and Oliveira (2004) based upon specimens from Brazil, we found that the absence of wings, larger lateral leaflets, lack of interjected leaflets or small interjected leaflets, and irregular acumens occur throughout its entire range.

Solanum calvescens has been differentiated from other tuber bearing species on the basis of very small acumens, anthers not clearly delimited from the filaments, flowers white or purple, and triploid ploidy (Correll, 1962; Hawkes and Hjerting, 1969). Both authors stressed the particular stamens of S. calvescens, similar to S. maglia, not being basally cordate. While the stamens of plants identified as S. calvescens are somewhat atypical, they are not like S. maglia that possess “barrel” shaped stamens without a clear distinction between stamens and filaments. The specific characters observed in the stamens S. calvescens points partly towards the characteristic form of a male sterile plant: small, distorted and pale.

Along its wide distribution, S. chacoense has been found growing with S. kurtzianum, S. microdontum, S. tarijense, and S. spegazzinii. Hybrids have been reported between several of these species. Solanum chacoense was the first tuber-bearing species investigated for introgressive hybridization. Hawkes (1962) considered that hybridization with S. microdontum in northwest Argentina might be responsible for its extended distribution at higher altitudes. Juned et al. (1988) studied populations from Paraguay and Argentina using morphological and isozyme markers and found that introgression could not explain the range of variation detected in Córdoba province. They proposed that regional diversity and clinal variation according to altitude were responsible for the detected variability. Miller and Spooner (1996) investigated the hybrid nature of upland populations of S. chacoense using morphological and molecular data (RAPDs and RFLPs). They distinguished upland from lowland populations on the basis of morphological data; this was partially supported by RAPDs but not by RFLP data. Introgressive hybridization with other species does not appear to be responsible for the variability observed in S. chacoense.


Hawkes, J.G. 1962. Introgression in certain wild potato species.
Euphytica 11: 26-35.

Correll, D.S. 1962. The potato and its wild relatives.
Contr. Texas Res. Found., Bot. Stud. 4: 1-606.

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

Morton, C.V. 1976. A revision of the Argentine species of Solanum.
Pp. 1-260. Academia Nacional de Ciencias, Córdoba, Argentina.

Juned, S.A., M.T. Jackson & J.P. Catty 1988. Diversity in the wild potato species Solanum chacoense Bitt.
Euphytica 37: 149-156.

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.

Miller, J.T., & D.M. Spooner 1996. Introgression of Solanum chacoense (Solanum sect. Petota) upland populations reexamined.
Syst. Bot. 21: 461-475.

Mentz, L.A. & P.L. de Oliveira 2004. Solanum (Solanaceae) na região sul do Brasil.
Pesquisas, Bot. 54: 1-327.

Matesevach, M. & G.E. Barboza 2005. Flora fanerogamica Argentina: fasciculo 87. 256. Solanaceae, parte 13. Tribu 1. Solaneae, parte 2. Solanum subgen. Potatoe, sect. Petota.
Cordoba, Argentina: ProFlora Conicet.

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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