Solanum viarum Dunal, Prodr. [A.P. de Candolle] 13(1): 240. 1852.

Aubriot, Xavier & Knapp, Sandra, 2022, A revision of the " spiny solanums " of Tropical Asia (Solanum, the Leptostemonum Clade, Solanaceae), PhytoKeys 198, pp. 1-270 : 1

47. Solanum viarum Dunal, Prodr. [A.P. de Candolle] 13(1): 240. 1852.

Figs 3H , 73C-E

Solanum khasianum C.B.Clarke var. chatterjeeanum Sengupta, Bull. Bot. Surv. India 3: 413. 1961. Type. India. Tamil Nadu: "Madras, Nilgiris district", 1075 m, 17 Jul 1960, K. Subramanyam 10413 (holotype: CAL [CAL-10413A]; isotypes: CAL [CAL-10413B, CAL-10413C]).

Type.

Brazil. São Paulo: sin. loc., P. Lund 799 (holotype: G-DC [G00145818, F neg. 6816, IDC microfiche 800-61.2080:I.1]) .

Description.

Vorontsova and Knapp (2016: 365-368); http://www.solanaceaesource.org/solanaceae/solanum-viarum.

Distribution.

Solanum viarum is widely distributed in tropical Asia, particularly in China and northern India; native to Brazil, this species is widely adventive and can be invasive (see below). Solanum viarum has been formally assessed as of Least Concern (LC) on the IUCN Red List ( Knapp 2020).

Common names.

China. mao guo qie ( Zhang et al. 1994). India. Andaman and Nicobar Islands: jangli baigun (Basu ANC-6866).

Discussion.

Solanum viarum is a member of the Acanthophora clade (sensu Stern et al. 2011; Gagnon et al. 2022), along with S. aculeatissimum , S. capsicoides , and S. mammosum . All members of the clade can be distinguished by their pubescence of simple trichomes (derived from stellate midpoints, see Whalen 1984) on upper leaf surfaces. It can be distinguished from the rest of the members of the clade in tropical Asia in its dense and fine glandular pubescence on all parts, relatively small fruits, unwinged seeds, and small, pale greenish cream flowers. It is most similar to S. aculeatissimum , which has similarly small berries, but differs from that species in its deltate, rather than long acuminate, calyx lobes and puberulent, rather than stipitate-glandular, ovary. The prickles of S. viarum are often slightly curved and of uniform length, while those of S. aculeatissimum are straight and of varying lengths.

Solanum viarum and S. aculeatissimum were both previously known as S. khasianum (see Babu and Hepper 1979), but subsequent monographic work across the native range of these taxa ( Nee 1979) clarified that the two were distinct.

Solanum viarum has potent antioxidant compounds similar to those used medicinally from other species in tropical Asia (e.g., S. insanum , see Uses, pg. 18-20) and has potential for medicinal or other use in the area ( Wu et al. 2012). In Bhutan it has been recorded as being grown as a source of the alkaloid solasodine ( Mill 2001).

Solanum viarum (under the common name soda apple or tropical soda apple) has been classified as a noxious weed in the southern United States and Australia (https://www.ars.usda.gov/news-events/news/research-news/1999/digging-burning-thwart-soda-apple-weed/; https://weeds.dpi.nsw.gov.au/Weeds/Details/186). Where we have seen it in tropical Asia it is similarly aggressive and can take over fields and pastures.

Specimens examined.

See Suppl. materials 1-3.

Figures

Figure 3. Diversity of inflorescences and flowers in tropical Asian spiny solanums A lax, spreading inflorescences and stellate flowers of Solanum violaceum (Sampath Kumar et al. 126945, India) B condensed, recurved inflorescences and stellate flowers of S. multiflorum (Sampath Kumar et al. 126950, India) C inflorescences and large stellate flowers of S. involucratum (field photograph, unvouchered, Vietnam) D inflorescences and stellate flowers of S. pubescens with unequal stamens, one long and recurved (Sampath Kumar et al. 126956, India) E large rotate flower of S. insanum with abundant interpetalar corolla tissues (Sampath Kumar et al. 126918, India) F many flowered inflorescence and infructescence of S. pseudosaponaceum (field photograph, unvouchered, Philippines) G many flowered inflorescences of S. torvum; flowers with well-developed interpetalar corolla tissues (Suksathan et al. PS 3815, Thailand) H small stellate flowers of S. viarum (Sampath Kumar et al. 126944, India). Photograph credits: A, B, D, E, H X. Aubriot C M. Nuraliev F D. Tandang G D. Pedersen.

Figure 73. Introduced species of Solanum. Solanum torvum Sw. A habit (Meeboonya et al. RM 267, Thailand) B detail view of an inflorescence with flowers and fruits (Meeboonya et al. RM 267, Thailand). Solanum viarum Dunal C habit (Sampath Kumar et al. 126976, India) D detail view of a flower (Sampath Kumar et al. 126923, India) E detail view of a fruit (Sampath Kumar et al. 126923, India). Solanum wrightii Benth. F habit (Meeboonya et al. RM 271, Thailand) G detail view of flowers (Meeboonya et al. RM 271, Thailand) H detail view of fruits (Meeboonya et al. RM 271, Thailand). Photograph credits: X. Aubriot.