Solanaceae Source

A global taxonomic resource for the nightshade family

Solanum iopetalum

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Citation author: 
(Bitter) J. G. Hawkes
Citation: 
Bull. Imp. Bur. Pl. Breed. Genet., Cambridge 30. 1944.
Type: 
Based on Solanum verrucosum var. iopetalum Bitter, Repert. Spec. Nov. Regni Veg. 11: 455. 1912.
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M.
Habit: 
Herbaceous tuber-bearing perennials 0.3-0.75 m tall. Stems 3-5 mm in diameter at base of plant.
Sympodial structure: 
Sympodial units typically 3-6-foliate.
Leaves: 
Pseudostipules to 5-15 mm long, lunate. Leaves odd-pinnate, 9-35 cm long, 6-27 cm wide, strigose, puberulent or pubescent adaxially and abaxially; petioles 2-10 cm long; lateral leaflet pairs 2-4, the first two pairs often equal or only gradually diminishing in size towards the base of the leaf; most distal lateral leaflets 4-14 cm long, 1.8-5 cm wide, ovate to more commonly broadly elliptical, apex acute to acuminate, base oblique, sessile, or with petiolules up to 6 mm long, rarely decurrent on the rachis; terminal leaflet 6-13 cm long, 2-4 cm wide, elliptical, apex acute to acuminate, base cuneate; interjected leaflets 0-10.
Inflorescences: 
Inflorescence a dichasially branched, ebracteate, monochasial or dichasial cyme, 2-3 forked, generally in the distal half of the plant, with 3-17 flowers, all flowers perfect, peduncle 1-9.8 cm long; pedicels 13-25 mm long, articulate between the proximal ¼ and the distal ¼.
Flowers: 
Flowers with the calyx 5-8 mm long, lobes acute to long-attenuate, acumens minute to 3.5 mm long. Corollas 1.9-4 cm in diameter, pentagonal to rotate, acumens 2-3 mm long, edges of corolla flat, not folded dorsally, white or very light violet to dark violet, usually darker abaxially than abaxially. Anthers 5-6 mm long, connate, yellow, apically poricidally dehiscent and often maturing to a short introrse apical slit, filaments 1-4 mm long. Ovary with style 8-10 mm long, exceeding stamens by 3-5 mm, straight, with stigma globose.
Fruits: 
Fruits 1-2 cm long, ellipsoid to conical, light to medium green, often with smooth to raised white dots.
Seeds: 
Seeds from living specimens green-white throughout, ovoid, ca. 2 mm long, with a thick covering of “hair-like” lateral walls of the testal cells that make the seeds mucilaginous when wet. Removal of these hair-like lateral walls by enzyme digestion reveals a honeycomb pattern at their base.
Chromosome number: 

2n = ploidy missing =72 voucher missing = (Spooner & Hijmans 2001)

Distribution: 

Widely distributed from central Mexico (Jalisco to Querétaro), south to Oaxaca, 1700-3350 m; in rich organic soil, along roadsides, among bushes, edges of cultivated fields, in areas of alder, pine, oak, and fir forests.

Phenology: 
Flowering and fruiting July through November.
Phylogeny: 

Solanum iopetalum belongs to the potato clade of Solanum (Bohs, in press). Spooner and Sytsma (1992) placed S. iopetalum and all other North and Central American members of the Iopetala group (S. guerreroense, S. iopetalum, S. schenckii) in a terminal clade baed on chloroplast DNA restriction site data. Included here are four polysomic polyploid 6x(4EBN) species; this ploidy/EBN shared in North and Central America only with S. demissum. The members of the Iopetala group are very similar to each other and to one of their putative genome contributors, S. verrucosum (diploid). The members of the Iopetala group also are morphologically similar to S. stoloniferum, 4x(2ENB), but are separated from it by strong EBN-based crossability barriers. There are no clear morphological characters uniting members of this group, their parental origins are unknown and, like other polyploids, they could have multiple origins. These factors make them difficult to classify in any phylogenetic classification and frustratingly difficult to identify without well-preserved complete flowering and fruiting specimens. We define the Iopetala group largely based on the 6x(4EBN) crossability.

Commentary: 

Solanum iopetalum is most similar to S. guerreroense and S. hougasii (Spooner et al. 1995). It has fewer interstitial leaflets (0-10) than S. guerreroense (8-19), and ellipsoid to conical fruits (globose in S. hougasii).

References: 

Spooner, D.M. & K.J. Sytsma 1992. Reexamination of series relationships of Mexican and Central American wild potatoes (Solanum sect. Petota): evidence from chloroplast DNA restriction site variation.
Syst. Bot. 17:432-448.

Spooner, D.M., R.G. van den Berg, & J.B. Bamberg 1995. Examination of species boundaries of Solanum series Demissa and potentially related species in series Acaulia and series Tuberosa (sect. Petota).
Syst. Bot. 20: 295-314.

Spooner, D.M. & R.J. Hijmans 2001. Potato systematics and germplasm collecting, 1989-2000.
Amer. J. Potato Res. 78:237-268; 395.

Spooner, D.M., R.G. van den Berg, A. Rodríguez, J. Bamberg, R.J. Hijmans, & S.I. Lara-Cabrera 2004. Wild potatoes (Solanum section Petota; Solanaceae) of North and Central America.
Syst. Bot. Monog. 68: 1-209 + 9 plates.

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.

Genetics: 

Chloroplast DNA restriction site data available in: Spooner and Sytsma (1992).

Taxonomic name: 
Solanum iopetalum (Solanaceae)
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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith