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Lima bean, Sugar bean [Phaseolus lunatus L.]


The situation in Japan and information from the NIAS genebank
The lima bean is called "Lai mame" or "Aoi mame".It is considered to have been introduced into Japan during the Edo period (16th to 18th century) (Hoshikawa 1981).
This legume is not a popular crop. In Japan, dry seeds are cooked as "nimame" (boiled bean sweetened with sugar).
The available archaeological evidence supports the hypothesis that the small seeded lima beans have been domesticated in Mesoamerica while the large-seeded types have been domesticated in South America.
Based on the review of the available information, Salgado et al.(1995) show that wild forms can be divided into two groups, one with smaller seeds and a very extensive distribution that includes Mexico, Central America, and the eastern slope of the Andes, and the other with a more restricted distribution on the western slope of the Andes in Equador and northern Peru.
Their results of the analysis of seed protein by SDS-PAGE confirmed this subdivision and, additionally, showed that the large-seeded cultivars have been domesticated from the large-seeded wild lima beans in western South America. For the small-seeded lima bean cultivars, it was not possible to determine a domestication center.
The genus Phaseolus, together with the closely related genus Vigna, forms a very complicated taxonomic group, so called Phaseolus-Vigna complex. Verdcourt (1970) proposed a very restricted concept of Phaseolus, limiting it exclusively to those American species with a tightly coiled style and pollen grains lacking course reticulation, hence, promoting significantly the concept of Vigna.
Marechal et al. (1978) followed Verdcourt and presented a monograph on the Phaseolus-Vigna complex. Their taxonomic system is generally accepted now.
There are some 30 species described in their monograph. They recognized two botanical varieties in the P.lunatus, i.e., var.lunatus (Lima bean) and var.silvester (wild ancestral form).
They adopted the concept of cultigroups and subdivided var.lunatus (Lima bean) into three cultigroups, i.e., cv-gr.SIEVA, cv-gr.POTATO and cv-gr.BIG LIMA. Cultigroup SIEVA is characterized by the moderate size of flat seeds and is cultivated mainly in Meso America. Cultigroup POTATO is characterized by the small and round shaped seeds. The synonym P.bipunctatus is applied especially for this form.
It is mainly distributed around the West Indies. Cultigroup BIG LIMA is characterized by very large flat shaped seeds and is cultivated mainly in the Andean region of 1800-2800m in altitude. P.inamoenus, P.limensis and P.lunatus var.macrocarpus are the synonyms applied for this cultigroup. 2n=22.
Pole type cultivar and wild form of P.lunatus are twining, perennial herbs, 2-4m tall, with enlarged rootstock (Purseglove, 1974). Annual and small bush forms, 30-90cm high, have been developed in cultivation. Flower size is smaller than that of P.vulgaris or P.coccineus. Flower color is usually pale green, occasionally violet.
Seeds are very variable in size, shape and color, 1-3cm long, ranging from flat-seeded types to rounded seeds of potato types with cream, red, purple, brown or black, and various types of mottled color. Hilum is white with translucent lines radiating from it to outer edge of testa. Pod is oblong, generally recurved, 5-12 x 1.5-2.5cm, 2-4 seeded.
Lima bean is grown for dried beans (Purseglove,1974). Care is required in preparation as some cultivars contain dangerous amounts of hydrocyanic acid. This is dissipated by boiling and changing the cooking water. The green shelled beans are cooked as a vegetable and the young pods and leaves are sometimes used for this purpose.
Hoshikawa,K. 1981. Lai mame (Lima bean). in "Shokuyou Sakumotu" (Food Crops). Yoken-do, Tokyo. (in Japanese) pp.491-494.
Marechal,R., J.M.Mascherpa and F.Stainer. 1978. Etude taxonomique d'un groupe complexe d'speces des genres Phaseolus et Vigna (Papilionaceae) sur la base de donnees morphologiques et polliniques, traitees par l'analyse informatique. Boissiera 28 : 1-273.
Purseglove, J.W. 1974. Phaseolus lunatus In "Tropical Crops : Dicotyledons." London : Longman. pp.296-301.
Salgado,A.G., P.Gepts and D.G.Debouck, 1995. Evidence for two gene pools of the Lima bean, Phaseolus lunatus L., in the Americas. Genetic Resources and Crop Evolution 42:15-28.
Smartt,J. 1990. Grain Legumes. Cambridge University Press. pp.85-139.
Verdcourt,B. 1970. Studies in the Leguminosae - Papilionoideae for the "Flora of Tropical East Africa" : IV. Kew Bulletin 24.