Solanum retroflexum Dunal, Prodr. [A. P. de Candolle] 13(1): 50. 1852

Knapp, Sandra, Barboza, Gloria E., Bohs, Lynn & Saerkinen, Tiina, 2019, A revision of the Morelloid Clade of Solanum L. (Solanaceae) in North and Central America and the Caribbean, PhytoKeys 123, pp. 1-144 : 85-90

14. Solanum retroflexum Dunal, Prodr. [A. P. de Candolle] 13(1): 50. 1852 Figures 42 , 43

Type.5

South Africa. Eastern Cape: Graaff Reinet ( “Graafeynet”), 3000-4000 ft, 1838, J.F. Drège 7864b (lectotype designated by Särkinen et al. 2018, pg. 134: G-DC [G00144331]; isolectotypes: K [K000414172], S [acc. # S-G-5707]).

Description.

Annual to perennial herbs to 0.6 m tall, often woody at the base. Stems terete or ridged, 0.3-0.6 cm in diameter, green to yellowish-brown, prostrate or erect, the lowermost lateral branches usually spreading, if stems ridged the ridges sometimes spinescent, not markedly hollow; new growth sparsely to densely pubescent with glandular and/or eglandular simple spreading uniseriate 1 –5(– 8)-celled trichomes 0.1-0.8 mm long; older stems glabrescent, straw coloured. Sympodial units difoliate, the leaves not geminate. Leaves simple, (0.5-) 1.5-7.5 cm long, 1.5-5.5 cm wide, rhomboidal to lanceolate, slightly discolorous; adaxial surface green sparsely to densely pubescent with simple uniseriate trichomes like those on stem evenly spread along lamina and veins; abaxial surface slightly paler, more densely pubescent along veins and lamina; major veins 3-7 pairs, pairs not strictly opposite, not prominent; base truncate then abruptly attenuate along the petiole; margins shallowly toothed, the teeth rounded; apex acute, the tip sometimes rounded; petioles (0.5-) 1.5-3.5 cm long, sparsely to densely pubescent with simple uniseriate trichomes like those of the stems. Inflorescences 1.8-3.0 cm long, internodal, unbranched, with 3-7 flowers clustered towards the tip of the rhachis (sub-umbelliform), sparsely to densely pubescent with glandular and /or eglandular simple uniseriate trichomes like those on stems; peduncle 1.5-3.5 cm long, erect, green; pedicels 1.0-1.5 cm long, 0.3-0.6 mm in diameter at the base, 0.4-0.6 mm in diameter at the apex, recurving but not fully reflexed, pubescent like the peduncle, becoming woody, green or yellow-brown, articulated at the base; pedicel scars spaced 0-0.5 mm apart. Buds globose, the corolla 1/3 exserted from the calyx before anthesis. Flowers 5-merous, all perfect. Calyx tube 1.0-1.7 mm long, campanulate, the lobes equal, 1.0-1.5 mm long, less than 1 mm wide, oblong with rounded tips, green, sparsely pubescent with simple uniseriate trichomes like of the inflorescence. Corolla 11-16 mm in diameter, white, with a yellow basal star, stellate, lobed to 1/2-2/3 towards the base, the lobes 5.0-6.0 mm long, 2.5-2.7 mm wide, spreading to reflexed, densely papillate-pubescent abaxially with simple uniseriate trichomes, these denser on tips and margins. Stamens equal; filament tube minute; free portion of the filaments 1.2-1.5 mm long, glabrous or adaxially pubescent with tangled 6-8-celled simple uniseriate trichomes; anthers 1.3-1.8(-2.0) mm long, 1.0-1.5 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age and drying, the connective becoming brownish in dry material. Ovary rounded, glabrous; style 1.9-2.2 mm long, slightly curved, pubescent with simple uniseriate trichomes 0.2-0.5 mm long in the basal 1/3 where included in the anther cone, exserted 0.5-1.5 mm beyond anther cone; stigma capitate, the surface minutely papillate. Fruit a globose to ellipsoid berry, 6-10 mm in diameter, purple-black at maturity, opaque, the pericarp thin, matte with a glaucous cast; fruiting pedicels 10-15 mm long, 0.4-0.6 mm in diameter at the base, 1.0-1.2 mm in diameter at the apex, becoming woody, recurving to deflexed, pale green to yellow-brown, persistent, spaced 0-0.5 mm apart, not falling with the fruit, remaining on the plant and persistent on older inflorescences; fruiting calyx not accrescent, the tube 1.0-1.5 mm long, the lobes 1.5-2.0 mm long, strongly reflexed. Seeds (5 –)12– 35 per berry, 1.3-1.5 mm long, 1.6-1.8 mm wide, flattened and tear-drop shaped with a subapical hilum, yellow to brown, the surfaces minutely pitted, the testal cells rectangular to pentagonal in outline. Stone cells absent. Chromosome number: 2n =4 × =48 (see Särkinen et al. 2018).

Distribution.

(Figure 44 ) Solanum retroflexum is native to southern Africa but introduced to North America as a garden plant. In North America it is mostly cultivated.

Ecology.

A cultivated plant or a rare adventive in flower beds and other cultivated areas.

Common names.

United States of America. Sunberry ( Schilling 1981), Wonderberry (see Heiser 1969).

Uses.

In its native South Africa, the berries are used for jam or as a fruit ( Heiser 1969, Särkinen et al. 2018); its cultivation by Luther Burbank was also as a jam fruit ( Heiser 1969).

Preliminary conservation status ( IUCN 2017).

Least Concern (LC). Solanum retroflexum is a rare adventive species in North America; for conservation status in its native range see Särkinen et al. (2018).

Discussion.

In its native range S. retroflexum is a species that shows great variation in its indumentum, the trichomes varying from eglandular to glandular and the leaves from nearly glabrous to densely pubescent. In the geographic region treated here, it has only been collected sporadically from cultivation and appears not to escape or naturalise. The species can be distinguished from other morelloids in North America based on a character combination of inflorescences with 1-4 flowers, filaments 1.2-1.5 mm long, strongly reflexed calyx lobes in fruit, and matte purple berries that lack stone cells and drop without the pedicels. Solanum americanum has similar small anthers and persistent pedicels, but the berries are very shiny and contain stone cells.

Solanum retroflexum is a tetraploid of uncertain parentage (see discussion in Särkinen et al. 2018). The berries are used in a local jam industry in South Africa ( Viljoen 2011) and this is the species introduced as the “wonderberry” by Luther Burbank in the 1930s ( Heiser 1969). The story of the mystery surrounding the identity of Burbank’s " wonderberry" is told in detail in Heiser (1969); it was variously considered a fraud or a case of mistaken identity. Burbank contended he had created the “wonderberry” through hybridisation of " S. guineense " (= S. scabrum ) and " S. villosum " (probably = S. nitidibaccatum ). Various correspondents (see Heiser 1969) suggested it was actually the "garden huckleberry" ( S. scabrum ) or one of the native black nightshades from North America. Stebbins and Paddock (1949) suggested that the true identity of the “wonderberry” was S. nigrum , a species occasionally found in agricultural fields in the western United States. Examination of specimens grown from the original seeds sold by John Childs, the sole distributor of Burbank’s “wonderberry”, have shown that these were plants of S. retroflexum , but how Burbank came to grow them is still not known. Typification details for the synonyms of S. retroflexum can be found in Särkinen et al. (2018).

Specimens examined.

See Suppl. materials 1 and 3.

Figures

Figure 42. Solanum retroflexum Dunal. A Habit B flower. Drawing by M. L. Szent-Ivany, first published in Symon (1981), courtesy of the Board of the Botanic Gardens and State Herbarium (Adelaide, South Australia), reproduced with permission (previously also published in " PhytoKeys 106 ").

Figure 43. Solanum retroflexum Dunal. A Habit B glandular indumentum present in some individuals C flowers D mature, slightly ellipsoid matte black-purple fruits with reflexed calyx lobes (A, C Nijmegen accession A 1450022 B Nijmegen accession 944750163 C Nijmegen accession A 14750023 D Nijmegen accession A 14750025). Photos by S. Knapp and G. van der Weerden (previously published in " PhytoKeys 106 ").

Figure 44. Distribution of Solanum retroflexum Dunal (specimens mapped are both cultivated and adventive).