Solanum lycopersicum can be distinguished from the wild tomatoes by its bright red or yellow ripe fruit, usually autogamous flowers with the styles always included in the staminal column and its copious, long, trichomes that are often > 3 mm long. The only other tomato species with red, yellow or orange fruits are S. pimpinellifolium (with much smaller fruit and stellate, rather than pentagonal flowers) and the Galápagos endemics S. cheesmaniae and S. galapagense (with orange fruit and foliage smelling of limes). Solanum lycopersicum has been recorded on all continents except Antarctica, and is a widespread escape wherever it is cultivated, although in temperate climates it rarely survives the freezing conditions of winter. The species originated from western South America, but whether or not it ever existed in the wild or instead was derived by human selection from the closely related S. pimpinellifolium will be impossible to ascertain given its long use and wide transportation all over the world. The observation (see discussion of S. pimpinellifolium) that the two species hybridize in northern Peru and southern Ecuador lends some support to Brezhnev’s (1958, 1964) suggestion that the two are conspecific. Despite this possibility, we retain the two taxa as distinct species. Both names are widely used in the agricultural literature, and the two species are relatively easy to distinguish in the absence of hybridization. The use of fine molecular techniques is currently being developed for isolation of characters of breeding importance in elite breeding lines in the cultivated tomato as the genetic base has narrowed (Zamir 2001; Yang et al. 2004). These techniques may help to identify genes of potential utility in examining the history of cultivation and the relationships of these elite breeding lines to heritage and semi-feral cultivars.Most previous workers in tomatoes have suggested that the cultivated tomato was derived from small-fruited forms called by many authors “var. cerasiforme”. Research into the genetic control of fruit shape and size in tomatoes has shown that the incredible variation in fruit shape seen in cultivars of S. lycopersicum is controlled by a very few tightly linked loci (e.g. van der Knaap et al. 2002, 2004) and that the small-fruited forms are not ancestral, but instead a mixture of wild and cultivated forms (Nesbitt & Tanksley 2002). Fruit shape in S. lycopersicum is a very interesting character state with which to explore the effects of few genes on broadly divergent morphology, and is being actively studied, especially using newly developed genomics tools.Brezhnev’s (1958, 1964) classification of S. lycopersicum is replete with subspecific taxa. Brezhnev attempted to describe all details of the cultivars known to him. He classified escaped plants with smallish fruits as “subsp. subspontaneum” (a nomen nudum), indicating his belief that these plants represented feral or less developed forms of the cultivated tomato. He recognized six varieties of this subspecies, vars. “cerasiforme”, “pyriforme”, “pruniforme”, “elongatum”, humboldtii and “succenturiatum”, most of which are nomina nuda. These varieties were then seen to “rejoin” genetically to give rise to two geographical groups (Mexican and Peruvian). The large-fruited, highly morphologically aberrant forms were classified as “subsp. cultum” (again a nomen nudum), within which he recognized several “grex concultorum”, each defined geographically (“australioeuropeum”, “occidentalieuropeum”, “australirossicum”, “mediirossicum”, borealirossicum” and “borealiamericanum”). Each “grex concultorum” contained 3-7 cultivars with Russian common names (such as ‘Comet’ and ‘Korol Gumbert’). As with “subsp. spontaneum”, the “grex concultorum” were depicted in his diagram as derived from an amalgamation of all three varieties of “subsp. cultum”. His classification was an attempt to bring order to the huge number of tomato cultivars then grown in the Soviet Union, linking them to their supposed places of origin. Although Brezhnev’s work has been largely neglected by tomato workers in the United States and western Europe, it will be essential for anyone interested in examining the identities of cultivars and heritage varieties from that time. Khrapalova (2001) gave a complicated series of varietal and subvarietal names to many of these variants, but none of her names was validly published.In general, S. lycopersicum only persists as a feral plant in subtropical or tropical regions; frost kills the plants and the commonly cultivated forms behave as annuals, although they can persist for several years in the absence of frosts. Human transportation of plant material, both intentional and accidental, accounts for the wide distribution of S. lycopersicum.Solanum pseudolycopersicum has sometimes been considered a synonym of S. peruvianum owing to Jacquin’s description, indicating it to have hairy, yellow fruits (“Baccae in eadam cerasi magnitudem raro superant; suntque globosae, villosae, flavescentes…”; Jacquin 1770-1771: 4), although Luckwill (1943: 23) recognized S. pseudolycopersicum as a synonym of S. lycopersicum (his L. esculentum subsp. galeni). The plate in Hortus Vindobensis (Jacquin 1770-1771), however, is clearly of S. lycopersicum, with ebracteate inflorescences and 3-foliate sympodia, and we suggest it is the best element to use as the lectotype of S. pseudolycopersicum.Lycopersicum spurium Link is perhaps a new combination based on Gmelin’s (1791) superfluous name Solanum spurium; Link’s protologue, however, makes no reference to Gmelin’s work or to the name “Solanum spurium”.Dunal thought that Blanco (Fl. filip. 133. 1835) had misapplied the name Solanum lycopersicum L. to an undescribed species of tomatoes and supplied the name Lycopersicon philippinarum. He explicitly stated that L. philippinarum was not based on specimens seen by him and added the query “An L. cerasiforme?” We neotypify L. philippinarum with the Kew duplicate of Merrill 14, which bears a label with a detailed discussion of the identity of Blanco’s concept of the tomato in the Philippines.We have not designated neotypes for the varieties described by Alefeld (1866) based on fruit color and shape variation in cultivated plants. These names, though validly published, are better regarded as cultivar names and treated under the International Code of Nomenclature of Cultivated Plants (Brickell et al. 2004). Alefeld (1866) did not designate any specimens, nor did he specify the exact region in which these particular cultivars grew.Suitable type material for some of the subspecific names coined by Russian tomato taxonomists could not be found at WIR; we did not propose neotypes in the hopes that future work on the relationships of cultivars will bring suitable type specimens or illustrations to light.The name Lycopersicon solanum Medik. listed in IPNI and earlier in Index Kewensis is a mistake in data entry; in Medikus’ Beobachten (1783) the name occurs not on page 245 as indicated in IPNI, but on page 383 (as Solanum lycopersicum) and 384 (as S. lycopersicum) with an attached figure of the anther cone (Fig. 38 of Medikus 1783). Medikus was not coining a new name, nor did he write Lycopersicon solanum.
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