Lablab purpureus L. (Sweet) is a native to India or South-East Asia. It is probably of an Asian origin and has been under cultivation since ancient times. Its wild forms are found in India. The crop was perhaps taken to tropical Africa and since then it might have been distributed to many countries like, Malaysia, Indonesia, Philippines, Mainland China, Papua New Guinea, Egypt, Sudan, East and West Africa, the Caribbean, Central and South America, etc.
Summarizing archeological findings, Fuller (2003) mentioned that Lablab bean is an ancient crop in India with the earliest find from before 3500 BC. However, Maass et al. (2005) did not find any evidence through AFLP studies to show that it had originated from elsewhere other than eastern and or southern Africa. Additionally, the wild forms collected from India and analysed through molecular marker studies were found genetically placed intermediate between wild and cultivated forms. And that these forms did not exist among the African collections led Maass et al. (2003) to hypothesise that the pattern of domestication and distribution of Lablab purpureus was from Africa to Asia. This was further affirmed by Maass et al. (2007) through studies relating to changes in seed characteristics between wild and cultivated forms. Still there is a school of thought, which believes in the dual centers of origin–Africa and Asia. Hoshikawa (1981) reported that it was introduced into Japan from China in 1654 where it is called “Fujimame” and young pods are used as vegetables.
Linneus (1754) described the species under Dolichos L. Adanson (1763) phrased the name Lablab for Dolichos L. The first of these species combined in Lablab adans was L. niger of Medikus (1787), based on Dolichos lablab L. A new epithet was required as Lablab would be tantonymous. Since Lablab niger is synonymous with D. Lablab, the two genera are homotypic by lectotypification.
Dolichos described in Flora India by Roxburgh (1832) contained seven varieties, of which five were cultivated and the rest were wild. The former was further divided into two categories: (a) Dolichos lablab var. typicus and (b) Dolichos lablab var. lignosus (Barker, 1911). Further division of the cultivated ones was proposed as short-day varieties with a photoperiod of 10–11 hours and the others relatively unaffected by day length (Rivals, 1953).
In 1965, Verdcourt proposed the rejection of Dolichos L. and in its place conservation of Dolichos Lam. with D. uniflorus Lam. as a type, because Dolichos L. with lectotype D. lablab L. would restrict the generic name Dolichos to D. lablab and possibly a few allies. However, the committee for Spermatophyta (1968) rejected the proposal for 3 specified reasons: (1) The species proposed as the type is not one of those originally included by Linnaeus; (2) the illegitimate name Lablab Adanson would need conserving; (3) botanists not agreeing with the segregation of Lablab and other generic splits could not use the name Dolichos L. for the combined genus.
Three years later, Verdcourt (1968) again proposed to retypify Dolichos L. this time by D. trilobus L. The committee for Spermatophyta (1970) found this proposal nomenclaturally preferable to the earlier one for the following seasons: (1) the proposed lectotype is one of the original Linnaean species. (2) the historical type of Dolichos Lam D. lablab is not separated from the genus as it was in the former proposal to conserve Dolichos Lam., so those choosing to include D. lablab as an inclusive Dolichos L. may still do so. (3) If D. lablab is held to be genetically distinct from Dolichos L. with the type D. trilobus, the name Lablab adons is available. Because, Lablab adons, was typified by Dolichos lablab L., it is not illegitimate unless the latter species is the type of Dolichos. (4) The proposal implies that the number of necessary new combinations will be reduced to about 30. However, the committee’s report also noted: “there is already a well–established type of the name Dolichos,, namely D. Lablab. Why not simply accept this and make all the necessary new combinations and go ahead on the basis of priority?” But the renewed proposal was rejected. However, Verdcourt (1970 a) put forth a new argument, which clearly demonstrated that the delimitation of Dolichos L. is by no means settled, but is still very much a matter of opinion, and that, when a future complete and detailed revision becomes available, impredictable segregations may prove necessary. The committee for Spermatophyte (1972) finally accepted the proposal, "over the objections of a strongly dissenting minority".
Verdcourt (1970) recognized three sub-species: (a) unicinatus, (b) purpureus and (c) bengalensis. He also mentioned the chromosome number of the species as 2n =22 or 24. Among the three subspecies, ssp. uncinatus was the ancestral form distributed mainly in East–Africa with small pods (40mm x 15mm); ssp purpureus. with large pods (100mm x 400mm) was the cultivated one with commercial varieties and ssp. bengalensis had linear oblong shaped pods (140mm x 10–25mm) and found widely spread in Asia. Although there were significant differences in respect of pod shape, it was supposed that ssp. purpureus and ssp bengalensis were genetically very similar and most of the domesticated material in India belongs either to ssp. purpureus or ssp. bengalensis. ssp uncinatus has been domesticated only in Ethiopia (Magness et al., 1971).
Verdcourt (1980) finally assigned it to monotypic genus Lablab and now widely known as Lablab purpureus L. (Sweet) although some, still, refer to it as Dolichos Lablab. Sometimes, it is also referred to as Lablab niger Medik, seldom though. The name “Lablab” is an Arabic or Egyptian name describing the dull rattle of the seeds inside the dry-pod.