Solanaceae Source

A global taxonomic resource for the nightshade family

Solanum pinnatisectum

Citation author: 
Dunal
Citation: 
Prodr. 13(1): 40. 1852.
Type: 
Mexico. Guanajuato: near León, W of Guanajuato, 1829, Méndez s.n. (holotype: G-DC! [F neg. 6752: F!, GH!, LL, MO, NY!, US!], [drawing: GH!]).
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M.
Habit: 
Herbaceous tuber-bearing perennials 0.4-0.7 m tall. Stems 3-6 mm in diameter at base of plant.
Sympodial structure: 
Sympodial units typically 3-6-foliate.
Leaves: 
Pseudostipules to 10 mm long, pinnatifid. Leaves odd-pinnate, 6-11.5 cm long, 4-6.5 cm wide, pilose and glandular adaxially and abaxially; petioles 1-4.2 cm long; lateral leaflet pairs 6-8, the second most distal lateral leaflets larger than the most distal, then the size of the lateral leaflets diminishing gradually towards the base of the leaf; most distal lateral leaflets 1.5-3 cm long, 0.3-8 cm wide, linear, lanceolate to elliptic-lanceolate, apex acute, base rounded to oblique, sessile, decurrent on the rachis; terminal leaflet 1.7-3.2 cm long, 0.3-7 cm wide, linear-lanceolate to linear-oblong, apex obtuse, base rounded to oblique, decurrent on the rachis; interjected leaflets absent.
Inflorescences: 
Inflorescence a dichasially branched, ebracteate, monochasial or dichasial cyme, 2-3 forked, generally in the distal half of the plant, with 3-12 flowers, all flowers perfect, peduncle 2.5-6 cm long; pedicels 15-25 (-30) mm long, articulate between the proximal ¼ and the distal ¼.
Flowers: 
Flowers with the calyx up to 4-10 mm long, lobes oblong, apiculate to caudate, acumens 1.5-6.5 mm long. Corollas 2.5-4 cm in diameter, stellate, without acumens, edges of corolla flat, not folded dorsally, white. Anthers 6-8 mm long, connate, yellow, apically poricidally dehiscent and often maturing to a short introrse apical slit, filaments 1-4 mm long. Ovary with style up to 9 mm long, exceeding stamens by 3-4 mm, straight, with stigma globose.
Fruits: 
Fruits 2 cm in diameter, globose or heart-shaped, with green stripes and white spots.
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 =24 voucher missing = (Spooner & Hijmans 2001)

Distribution: 

Central Mexico, states of Guanajuato, Jalisco, Michoacán, Querétaro, 1500-2200 m; frequently in cultivated or fallow fields, roadsides, tropical deciduous forests, mesquite-grasslands.

Phenology: 
Flowering and fruiting July through September.
Phylogeny: 

Solanum pinnatisectum belongs to the potato clade of Solanum (Bohs, in press). Spooner and Sytsma (1992) placed S. pinnatisectum and all other North and Central American diploids (exclusive of S. bulbocastanum, S. cardiophyllum, and S. verrucosum) in the basal “clade 1” of section Petota based on chloroplast DNA restriction site data. These Mexican diploids were studied by Spooner and Lara-Cabrera with morphological and microsatellite data (Lara-Cabrera and Spooner in press a) and AFLP data (Lara-Cabrera and Spooner in press b ). Spooner et al. (2004) placed S. jamesii and S. pinnatisectum in the Pinnatisecta group. These are the only two species in sect. Petota with pinnatifid pseudostipules, and they are united by AFLP data (Lara Cabrera and Spooner, in press b).

Commentary: 

Solanum pinnatisectum is one of the most distinctive wild potato species from North and Central America, easily distinguished by its 6-8 pairs of linear, lanceolate, to elliptic-lanceolate lateral leaflets. It would be hard to confuse with another species except for its putative hybrid with S. ehrenbergii, S. ×sambucinum (Hawkes 1990). Solanum ×sambucinum has lessfewer lateral leaflets (4-5) than S. pinnatisectum (6-8); S. ×sambucinum has lunate pseudostipules while S. pinnatisectum has pinnatifid pseudostipules; and S. ×sambucinum has lanceolate leaflets while S. pinnatisectum has linear-lanceolate leaflets.

Correll (1962) designated S. ×michoacanum as a nothospecies originating from a cross of S. bulbocastanum and S. pinnatisectum and is somewhat morphologically intermediate between them but has many fewer lateral leaflets than S. pinnatisectum (see below).

References: 

Lara-Cabrera, S. & D.M. Spooner Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: AFLP data.
Plant Syst. Evol.

Lara-Cabrera, S. & D.M. Spooner Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: morphological and microsatellite data.
Monogr. Syst. Bot., Missouri Bot. Gard.

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

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

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

Lara-Cabrera, S.I. 2001. Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: a morphological and molecular study.
Ph.D. Thesis, Plant Breeding and Plant Genetics Program, University of Wisconsin-Madison.

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). AFLP, morphological, and microsatellite data listed in: Lara-Cabrera (2001).

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