3313

1: Pulses

Phaseolus lunatus L.

Sp. Pl. ed. 2: 724 (1753).

LEGUMINOSAE

2n = 22

Phaseolus bipunctatus Jacq. (1770), Phaseolus limensis Macfad. (1837).

Lima bean, butter bean, Madagascar bean (En). Haricot de Lima, pois du Cap, fève créole (Fr). Indonesia: Java bean, kratok. Malaysia: kacang china, kacang jawa, kekara kratok. Philippines: sibatse simaron, patáni, zabache. Burma: Burma bean, white Burma. Thailand: thua rachamat; Vietnam: dâu ngu.

Lima bean has a neotropical origin with at least two centres of domestication: Central America (Mexico, Guatemala) for the small-seeded forms and South America (mainly Peru) for the large-seeded forms. In post-Columbian times, lima bean spread throughout America. Spaniards brought seeds across the Pacific to the Philippines and from there to Asia, mainly Java and Burma, and to Mauritius. The slave trade took them from Brazil to Africa, particularly in the western and central parts. Some large-seeded forms from the Peruvian coast were distributed to south-western Madagascar and southern California. It is now cultivated throughout the warmer parts of the world.

The crop is cultivated primarily for its immature and dry seeds. Particularly in Asia also immature sprouts, leaves and pods are consumed. In the Philippines, dry seeds are used to produce a high protein bean flour for enriching bread or noodles. Seeds and leaves are valued for their astringent qualities and consequently used as a diet for fever in traditional Asian medicine. After harvesting the pods, the vines are sometimes fed to cattle in Malaysia and Indonesia. Lima bean is also grown as a short duration cover or green manure crop in Malaysia.

Production statistics from many tropical regions are fragmentary and often agregated with other pulses. The United States is the world's largest producer with 20 600 ha under cultivation and 55 600 t green beans harvested in 1980. Madagascar is the second largest commercial producer with an area harvested of about 7 00 ha and a dry seed production of about 8 00 t, almost exclusively of the large, white-seeded types. Peru came third with dry seed production averaging 5 000—55 00 t from about 5 000—6 000 ha. In other countries, lima beans are grown mostly in gardens or as an intercrop in fields, without accurate estimation of acreage or production. In Asia, Burma is the major producer but no figures are available.

Dry seeds contain per 100 g edible portion: water 13.2 g, protein 14.4—26.4 g, fat 1.5 g, carbohydrates 58 g, fibre 3.7 g, ash 3.4 g. The energetic value averages 1450 kJ/100 g. Main limiting amino acids are methionine and cystine (with respect to total N 1.1 - 1.2 g per 16 g). Per 100 g edible portion green beans contain 1.3 g protein, green seeds 8.4 g, green leaves 0.6 g. Antimetabolic factors include protease inhibitors, lectins and cyanogenic glucosides (linamarin). Seed weight varies between 30 and 300 g/100 seeds. In Nigeria, cooking time of dry seeds is 60 - 90 min.

An annual or occasionally perennial herb, bushy forms up to 0.6 m, climbing forms 2—4 m tall. Roots, thin or swollen, up to 1.5— 2 m deep. Leaves trifoliolate; leaflets ovate and acuminate, 5—19 cm x 3— 11 cm. Inflorescences axillary racemes, up to 15 cm long, with many nodes and flowers; bracteoles persistent; calyx campanulate; corolla 0.7—1.0 cm wide; standard hood-shaped, pale green or violet; wings white or violet; keel sharply upturned, white or occasionally pigmented; stamens ten, diadelphous; style coiled with pubescent apical region; stigma ellipsoid, directed adaxially. Pods oblong, 5—12 cm x 2.5 cm, generally curved, sometimes with a hook-shaped top, 2—4-seeded. Seeds variable in size, shape and colour, kidney-shaped, rhomboid or round; colour uniform or speckled or mottled, white, green, yellow, brown, red, black or purple; often transverse lines radiate out from the hilum. Seedlings with epigeal germination, first leaves simple and opposite.

Germination and emergence occur 4 to 10 days after sowing. Vegetative growth accelerates after one month. Flowers appear 35—70 days and ripe pods 80—120 days after sowing under short daylength. In climbing types flowering and fruiting may extend throughout the wet season. Pollen and stigma mature synchronously and in close proximity within the unopened bud, favouring self-pollination. However, very often cross-pollination occurs as well. Shedding of buds, flowers and young pods amounts to 75—85%.

Within the species there are wild plants and cultivated plants, both groups are distinguished as botanical varieties: var. silvester Baudet and var. lunatus respectively. More in accordance with the International Code of Nomenclature of Cultivated Plants is the distinction of cultivar (cv.) groups below species level for the cultivated plants: cv.-group Sieva with medium-sized flat seeds, cv.-group Potato with small globular seeds and cv.-group Big Lima with large flat seeds.
Asian grown cultivars are usually classified into 4 groups:
- Java beans - medium sized, purplish-red to black with high amounts of HCN.
- Red Rangoon or Red Burma beans: small reddish beans, which are usually plump and sometimes with purplish spots. They contain traces of HCN.
- White Rangoon or White Burma beans: small white beans, usually plump and resembling small haricots. They usually contain traces of HCN.
- Lima beans: large plump white beans. Said not to contain HCN.

Lima bean contains day-neutral genotypes which flower in daylengths of 9—18 h and short-day types which require critical daylength of 11—12.3 h for flower initiation. Optimum temperatures range from 16 to 27 °C; frost is not tolerated. Normal annual rainfall is 900—1500 mm but the crop tolerates as little as 500—600 mm once established. It is grown in lowland tropical and subtropical areas but may climb to 2000—2500 m altitudes. Lima bean prefers well-aerated, well-drained soils with a pH 6.0—6.8. However, some cultivars tolerate acid soils with pH as low as 4.4.

Propagation is by seed. In the tropics, lima bean is cultivated in home gardens, or intercropped with cereals (maize, sorghum), roots and tubers (yam, cassava) or other crops (e.g. cotton, sugar cane). Sole cropping is more frequent in the United States, Madagascar and Peru.

Bush types are usually spaced 20—30 cm within rows and 60— 100 cm between rows, while climbing types may be planted on hills 90—200 cm apart. Seeds are often placed in the same hill as the companion crop in intercropping. Weeding is necessary during initial growth. In humid areas climbing types are staked, while in drier conditions (California, Madagascar and Peru), they may be left prostrate and irrigated 2—4 times before maturity. Fertilizer use is not a common practice in tropical areas. In the United States, Madagascar and Peru, lima bean is often grown as a sole crop; in other regions, rotation with food or cash crops is more frequent.

In the tropics, most serious diseases are web blight caused by Rhizoctonia sp., anthracnosis caused by Colletotrichum sp. and golden mosaic caused by a virus transmitted by white flies (Bemisia sp.). Root-knot nematodes (principally Meloidogyne), pod borers (Maruca sp., Cydia sp. and Etiella sp.) and bruchids (Acanthoscelides sp., Zabrotes sp.) are considered as serious pests. The crop shows, however, good rusticity in traditional cropping systems.

Green and mature pods of the climbing types are usually picked manually over a long period of time. In drier areas (Madagascar), whole plants are cut and left to dry in the field before removing the pods. Mechanical picking is only possible with erect cultivars maturing uniformly and setting pods well above the soil surface.

Throughout the tropics, dry seed yield ranges from 200—600 kg/ha in intercropping to 1 000—1 500 kg/ha in sole cropping. Under experimental conditions, production in pure stands may reach 2 000—2 500 kg dry seeds/ha for the bush types and 3 000—4 000 kg dry seeds/ha for the climbing types.

Pods, sometimes whole plants, are threshed usually by hand and seed is cleaned and sorted. Care should be taken with the threshing operation as the seeds are very brittle and easily damaged. In many tropical countries, seeds are sometimes stored in jars or baskets and covered with a layer of sand or ash to protect them against bruchid infestation. In the United States, green Lima beans are canned or frozen for consumption as a vegetable.

Over 2500 samples are available in the CIAT collection located at Cali (Colombia) with seeds coming mainly from South and Central America, West Africa, Madagascar and Burma. Other smaller gene banks exist in the United States, Brazil, Costa Rica and Nigeria (IITA, Ibadan). More than half of the primary gene pool is still uncollected and prospections are urgently needed in the primary centres of diversity of South and Central America, but also in the secondary centres of West Africa, Madagascar and South- East Asia.

Erectness, resistance to lodging and to web blight are prime criteria for the improvement of bush types. Earliness, photoinsensitivity, resistance to golden mosaic and suitability in intercropping are looked for in climbing types. Some promising genotypes in the humid tropics have already been identified among the climbing forms. A large secondary gene pool is available for improvement, and the following wild species have been successfully crossed with lima bean: Phaseolus jaliscanus Piper, Phaseolus metcalfei Wooton & Standley, Phaseolus polystachyus (L.) Britton, Sterns & Poggenb., Phaseolus ritensis M.E. Jones, Phaseolus salicifolius Piper and two other new yet unnamed species. Introgression of useful genes from the wild taxa (e.g. resistance to golden mosaic) has been observed in interspecific breeding materials.

Lima bean offers good prospects in both subtropical regions and semi-arid to humid tropics. Deep rooting, drought tolerance and high yielding potential are useful attributes for wide adaptation. Research priorities should first be devoted to full exploitation of the large genetic variation available in the primary gene pool.

Baudoin, J.P., 1982. Essais d'évaluation du haricot de Lima (Phaseolus lunatus L.) en vue de l'amélioration de sa culture en régions tropicales de basse altitude. Bull. Rech. Agron. Gembloux 17 (1): 3-16.
Duke, J.A., 1981. Handbook of legumes of world economic importance. Plenum Press, New York and London. p. 191-195.
Kay, D.E., 1979. Crop and Product Digest No. 3 - Food legumes. Tropical Products Institute, London. p. 225-245.
Lyman, J.M., Baudoin, J.P. & Hidalgo, R., 1985. Lima bean (Phaseolus lunatus L.). In: Summerfield, R.J. & Roberts, E.H. (Editors): Grain legume crops. Collins, London. p 477-519.

J.P. Baudoin

Baudoin, J.P., 1989. Phaseolus lunatus L.. In: van der Maesen, L.J.G. & Somaatmadja, S. (Editors): Plant Resources of South-East Asia No 1: Pulses. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea