Solanaceae Source

A global taxonomic resource for the nightshade family

Solanum malmeanum

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Citation author: 
Bitter
Citation: 
Repert. Spec. Nov. Regni Veg. 12: 447. 1913.
Type: 
Brazil. [Rio Grande do Sul]: Ijuhy [Ijuí], on sandy bank of stream in open denuded country, 5 Apr 1893, G.O.A. Malme in expedition of A.F. Regnell 756 (lectotype, S-05-0888, lower-right plant [Correll neg. 330, BM000881810, F-1603716, LL, NY, UC; F neg. 1, F-1463332], designated by Hawkes and Hjerting, 1969; isolectotypes, B, destroyed [F neg. 2838, F-621120, G00086401, MO-1691256, NY], S-05-8807 [Correll neg. 329, BM000881811, F-1603717, LL, MO-5588444, NY, UC1152250], S-05-8809 [Correll neg. 609, BM000881808, F-1603335, LL, MO-5588445, NY, UC1152333], UPS, US00027665 [Correll neg. 61, BM000881809, F-1604858, LL, NY, UC1152250], Z [Correll neg. 608, BM000881807, F-1603334, LL, NY, UC1152333]).
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M. & A. Clausen
Habit: 
Herbs 0.15-0.3 m tall in sunny situations, but in shady situations of woodlands or among tall grasslands up to 1 m tall, erect to semi-rosette when low-growing. Stems 1-3 mm in diameter at base of plant, green, unwinged, glabrous to densely puberulent; tubers typically borne singly at the end of each stolon.
Sympodial structure: 
Sympodial units tri- to plurifoliate, not geminate.
Leaves: 
Leaves odd-pinnate, the blades 7.5-15.5 x 4-8.5 cm, green, membranous to chartaceous, glabrous to pubescent adaxially and abaxially with hairs like those of the stems; lateral leaflet pairs 3-5, often subequal or decreasing in size gradually toward the base except for the most proximal 1 or 2 pairs that are greatly reduced in size; most distal lateral leaflets 3.3-6.5 x 2-4 cm, narrowly to broadly ovate, the apex acute to rounded, the base typically oblique, or cordate, to rounded, subsessile and slightly decurrent or with petiolules up to 2 mm long; terminal leaflet 3.2-5.8 x 1.5-3.9 cm, broadly ovate to broadly elliptic, the apex obtuse to more rarely acute, the base cuneate; interjected leaflets 0-4, sessile to short petiolulate, ovate to orbicular; petioles 1.3-4.5 cm, pubescent as the stems. Pseudostipules absent to 1 mm long, pubescent with hairs like those of the stem.
Inflorescences: 
Inflorescences 5-10 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 2-8 flowers, with all flowers apparently perfect, the axes pubescent with hairs like those of the stem; peduncle 1.5-6 cm long; pedicels 8-30 mm long in flower and fruit, spaced 1-10 mm apart, articulated at about the middle.
Flowers: 
Flowers homostylous, 5-merous. Calyx 3-7 mm long, the tube 1-2 mm, the lobes 1-6 mm, long acute to attenuate, the acumens 1-2 mm long, pubescent with hairs like those of the stem. Corolla 1.8-2.9 cm in diameter, stellate, almost pure white to white tinged with violet, the tube 1-2 mm long, the acumens ca. 0.2 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 4-5.5 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 9-12 mm x ca. 1 mm, exceeding stamens by 2-5 mm, straight, glabrous; stigma clavate to capitate.
Fruits: 
Fruit an ovoid to globose berry, 2.5-3 cm long, 2-2.5 cm wide, green when ripe, glabrous.
Seeds: 
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 = 2x = 24 voucher: Okada 5074 (BAL) (Hijmans, et al. 2007)

Distribution: 

Solanum malmeanum occurs widely in Argentina (Provs. Buenos Aires, Corrientes, Chaco, Entre Ríos, Formosa, Misiones, Santa Fé), Brazil (Río Grande do Sul), Paraguay (Boquerón, Central, Presidente Hayes, Itapará, Cordillera), Uruguay (Colonia, Maldonado). In palm forests, in or at the edges of woods, in cleared woods or inundated savannas, or as a weed in cultivated fields of maize, manioc, sweet potato, cotton, potato, sorghum, or Citrus plantations, in disturbed soil, coasts of rivers, 0-330 m in elevation.

Phenology: 
Flowering and fruiting from October to July.
Phylogeny: 

Solanum malmeanum is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. Within sect. Petota, Solanum malmeanum 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).

Commentary: 

Solanum malmeanum is sympatric with S. commersonii and S. chacoense. It can be differentiated from S. commersonii by its generally subequal uppermost lateral leaflets that do not decrease rapidly in size towards the base, by its generally petiolulate and larger lateral leaflets, and by its white flowers. The flowers are almost always white, although in a very few cases we have observed a small bluish spot very different from the characteristic dark stripes along the rays abaxially in flowers of S. commersonii. These populations could represent probable hybrids between S. malmeanum and S. commersonii. From S. chacoense it can be differentiated by its smaller and sometimes rosette-forming habit, by the obtuse to more rarely acute apex of the terminal leaflet, and generally by a shorter peduncle.

Hawkes and Hjerting (1969) and Hawkes (1990) considered S. malmeanum and S. commersonii as subspecies of S. commersonii and distinguished subsp. malmeanum from subsp. commersonii by the bases of leaflets decreasing gradually towards the base of the leaf, narrowly decurrent to petiolulate leaflets, low to median pedicel articulation, and corolla always white. Correll (1962) treated subspecies malmeanum as a form of S. commersonii and distinguished it from S. commersonii by the presence of at least some petiolulate leaflets and often two or more interjected leaflets. Mentz and Oliveira (2004) stated that some populations of S. malmeanum, when grown in glasshouses, did not maintain the white color of their flowers and consider these populations as possible hybrids. We have not seen this behavior in the populations we grew. Mentz and Oliveira (2004) considered S. malmeanum as a form of S. commersonii, but questioned the validity of even this rank on the basis of the differences stated.

References: 

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.

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

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

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.

Taxonomic name: 
Solanum malmeanum (Solanaceae)
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