The legume seeds or pulses, sometimes termed ‘grain legumes’, are second only to the cereals as a source of human food and provide the much-needed proteins to our predominantly vegetarian population. The relatively high protein content is attributed, in part, to the presence, on the roots of many legumes, of tubercles or nodules that contain nitrogen-fixing bacteria. These microorganisms are capable of using free atmospheric nitrogen to produce nitrates or nitrites, which can be readily used by the plants, thus augmenting their supply of nitrogenous material.
All the grain legumes are members of the family Fabaceae and belong to the three tribes, Vicieae, Hedysareae and Phaseoleae. Included in the first tribe are pulses such as lentil (Lens escukntaM.oen.ch), pea (Pisum sativum L.), chickpea (Cicer arietinum L.), grass pea or khesari dhal (Lathyrus sativus L.) and broad or horse bean (Viciafaba L.).The tribe Hedysareae includes groundnut (Arachis hypogaea L.), a crop which is more usually grown as an oilseed crop than as a pulse. Among the Phaseoleae are the soya bean [Glycine max (L.) Merr.], lablab bean [Lablab purpureus (L.) Sweet], common beans (Phaseolus spp.), cowpeas [Vigna unguiculata (L.) Walp.], pigeon pea [Cajanus cajan (L.) Millsp.], horse gram (Dolichos uniflorus Lam.), the ground beans [Voandzeia subterranea (L.) Thou] and Kerstingiella geocarpa Harms. in addition to minor pulses such as the sword and jack beans (Canavalia spp.). Another tribe Galegeae (Indigofereae) includes the cluster bean or guar [Cyamopsis tetragonoloba (L.) Taub.] which is used for the extraction of guar gum or as a green manure. To a minor extent, the tender pods are also cooked as a vegetable.
DOMESTICATION OF PULSES
Legumes have been an important crop ever since man started domesticating plants and have been a part of our cultural heritage. However, there has been a much greater development of leguminous crop plants in the New World. Chinese literature records the cultivation of soya bean between 3000 and 2000 BC. Legumes also featured in the cropping systems of the early Egyptian dynasties. The occurrence of pea and lentils have been reported by Helbaek (1966) at various archaeological sites such as Hacilar, Beidha and Jarmo, dating as far back as 7500 to 6500 BC. Archaeological remains of Pisum, Vicia and Lens, have been discovered by Renfrew (1966) from Neolithic sites in Greece.