Solanum laxissimum

Citation author:

Bitter

Citation:

Bot. Jahrb. Syst. 54, Beibl. 119: 7. 1916.

Type:

Peru. Junín: Jauja, Río Masamerich, upper Río Portochuelo, between Atac and Calabaza, 3100 m, 25 April 1913, A. Weberbauer 6640 (lectotype, designated by Ochoa 1999: MOL; isotypes, F-628999 [Correll neg. 895, BM000882061, UC1152313], F-628883 [Correll neg. 894, BM000882062, F-1593162, F-1603200, UC1152313], GH00077700 [Correll neg. 896, BM000882060, F-1603198, MO-5609719, UC1152312], US00027645 [Correll neg. 935, BM000882064, F-1602984, UC1152312], US-1444952 [Correll neg. 936, BM000882063, F-1602983, UC1152312]).

Last edited by:

David M. Spooner (2014)

Written by:

David M. Spooner & Diego Fajardo

Habit:

Herbs 0.5 to over 3 m tall, prostrate to erect. Stems 3-20 mm in diameter at base of plant, green to green mottled with purple, with straight wings 1 mm wide or more, usually glabrous to subglabrous; tubers typically placed one at the end of each stolon.

Sympodial structure:

Sympodial units tri- to plurifoliate, not geminate.

Leaves:

Leaves odd-pinnate, the blades 12.2-30 x 7-15.5 cm, medium green, sometimes with purple pigmentation abaxially, membranous to chartaceous, sparsely pubescent adaxially and abaxially; lateral leaflet pairs 3-5, subequal or leaflets decreasing gradually in size toward the leaf base, with the terminal leaflet equal to or slightly larger than the laterals; most distal lateral leaflets 2.5-7.5 x 1-3 cm, elliptic to lanceolate, the apex highly acuminate, the base with petiolules 2-6 mm, symmetrical; terminal leaflet 3.5-7.5 x 1-3 cm, elliptic to lanceolate, the apex acuminate elongated, the base rounded or obtuse, with secondary leaflets on the petiolule absent; interjected leaflets 0-6, sessile, ovate to orbicular; petioles 2.5-10 cm, glabrous to sparsely pubescent with hairs like those of the stems. Pseudostipules minute to 5 mm long, pubescent with hairs like those of the stem.

Inflorescences:

Inflorescences 5-10.5 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 13-36 flowers, with all flowers apparently perfect, the axes glabrous to subglabrous with hairs like those of the stem; peduncle 5-12.5 cm long; pedicels 11-32 mm long in flower and fruit, spaced 1-10 mm apart, articulated from the middle to the proximal fourth, rarely in the distal half.

Flowers:

Flowers homostylous, 5-merous. Calyx 9-14 mm long, the tube 1-2 mm, the lobes 4-8 mm, long attenuate, the acumens 0.4-3 mm long, glabrous. Corolla 1.2-2.5 cm in diameter, pentagonal to rotate, blue-violet to purple or pale violet, the rays light violet or white, the tube 1-2 mm long, the acumens 1-5 mm long, corolla edges flat, not folded dorsally, glabrous adaxially and abaxially, ciliate at the margins, especially at the tips of the corollas. Stamens with the filaments 1-2 mm long; anthers 4-8 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 7-9 mm x 0.3-0.5 mm, exceeding stamens by 1-2.5 mm, straight, glabrous; stigma subcapitate to capitate.

Fruits:

Fruit a conical berry, 1.5-2.3 cm long, 1.2-1.9 cm wide, light 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 Ochoa 11855 (CUZ)]; Hijmans et al. 2007

Distribution:

Endemic to central to southern Peru (Depts. Ayacucho, Cuzco, Huánuco, Junín and Pasco), in moist habitats, at forest edges; 670-4150 m in elevation.

Phenology:

Flowering and fruiting throughout the year.

Phylogeny:

Solanum laxissimum is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. Within sect. Petota, Solanum laxissimum is a member of a distinctive group of species formerly classified in series Conicibaccata (see below). 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:

Hawkes (1990) treated Solanum laxissimum as one of 40 species in Solanum sect. Petota series Conicibaccata Bitter, a group containing diploids (2n = 24), tetraploids (2n = 48), and hexaploids (2n = 72). The polyploids are mainly distributed from southern Mexico south to central Peru (one species in northern Bolivia), and the diploids from northern Peru to central Bolivia.

The species boundaries and relationships of members of series Conicibaccata have been studied using plastid DNA restriction sites (Castillo and Spooner, 1997), morphology (Castillo and Spooner, 1997; Fajardo et al., 2008), AFLPs (Jiménez et al., 2008), nuclear DNA (“waxy”) sequence data (Spooner et al., 2008), other nuclear DNA sequence data (in preparation by Fajardo and Spooner), and monographic studies (Hawkes, 1990; Hawkes and Hjerting, 1989; Ochoa, 1990, 1999). The plastid DNA restriction site and morphological data divide the diploids and polyploids into two clades or phenetic groups, respectively, but the morphological separation generally depends on the use of character states that sometimes overlap in range. The DNA sequence data show the polyploids to be of allopolyploid origin from the diploid members of the series and members of species outside of the series.

A monographic study in progress by Fajardo and Spooner, using the above data, and herbarium specimens, will recognize only 17 species. All are very similar, united as a group by conical fruits, leaves with generally parallel sided morphology, and narrowly ovate to elliptical leaflets. However, some unrelated species also have conical fruits, such as the Mexican diploid species S. hintonii Correll, S. lesteri Hawkes and Hjert. and S. trifidum Correll; the Mexican hexaploid species S. iopetalum (Bitter) Hawkes; and the Bolivian species S. circaeifolium Bitter. An additional problem is that some species possess ovoid fruits that are not absolutely distinct from the conical fruits of the above species or the globose fruits more common in the majority of the members of sect. Petota.

Solanum laxissimum is characterized by its acute or attenuate elongated leaflets with purple color sometimes present abaxially, sparsely pubescent leaves, winged stem, glabrous to subglabrous calyx, and pentagonal to rotate, often purple corolla.

References:

Bohs, L. 2005. Major clades in Solanum based on ndhF sequence data. Pp. 27-49. In: R. C. Keating, V. C. Hallowell, and T. B. Croat (eds.), A Festschrift for William G. D’Arcy: A Legacy of a Taxonomist. Missouri Botanical Garden, St. Louis.

Castillo, R. and D. M. Spooner. 1997. Phylogenetic relationships of wild potatoes, Solanum series Conicibaccata (sect. Petota). Syst. Bot. 22: 45-83.

Fajardo, D., R. Castillo, A. Salas, and D. M. Spooner. 2008. A morphometric study of species boundaries of the wild potato Solanum series Conicibaccata: a replicated field trial in Andean Peru. Syst. Bot. 33: 183-192.

Fajardo, D., and D. M. Spooner. 2011. Phylogenetic relationships of Solanum series Conicibaccata and related species in Solanum section Petota inferred from five conserved ortholog sequences. Syst. Bot. 36:163-170.

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

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

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

Jiménez, J. P., A. Brenes, A. Salas, D. Fajardo, and D. M. Spooner. 2008. The use and limits of AFLP data in the taxonomy of polyploid wild potato species in Solanum series Conicibaccata. Conserv. Genet. 9: 381-387.

Ochoa, C. M. 1990 [actual release date 13 June, 1991]. The potatoes of South America: Bolivia. Cambridge University Press, Cambridge, New York.

Ochoa, C. M. 1999. Las papas de sudamerica: Peru (Parte I). Lima, Peru: International Potato Center.

Spooner, D. M., F. Rodríguez, Z. Polgár, H. E. Ballard Jr., and S. H. Jansky. 2008. Genomic origins of potato polyploids: GBSSI gene sequencing data. The Plant Genome, a suppl. to Crop Sci. 48(S1): S27–S36

Taxonomic name:

Solanum laxissimum (Solanaceae)

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