Lablab purpureus (PROSEA)
Lablab purpureus L. (Sweet)
- Protologue: Hortus britannicus 1st ed.: 481 (1827).
- Family: Leguminosae
- Chromosome number: 2n = 22, 24
- Dolichos lablab L. (1753),
- Dolichos bengalensis Jacq. (1772),
- Lablab niger Medikus (1787).
- Lablab, hyacinth bean (En).
- Dolique lab-lab (Fr).
- Indonesia: komak.
- Malaysia: kara-kara, kekara.
- Philippines: bátau, itab, pardá.
- Burma: pe-gyi.
- Thailand: thua paep.
- Vietnam: dâu van.
Origin and geographic distribution
Lablab is believed to be native to India, South-East Asia or Africa. It is now found naturalized and cultivated in the tropics and subtropics, particularly in India, South-East Asia, Egypt and the Sudan.
In South-East Asia, lablab is popular as a vegetable, the young fruits eaten boiled like common beans or used in curries, immature green seeds are eaten boiled or roasted, leaves, young shoots and inflorescences are eaten boiled. In other parts of Asia, lablab is predominantly used as a pulse, often as dhal. Sometimes sprouted seeds are sun-dried and stored for future use as vegetable. Lablab is used also as fodder, hay, silage, green manure and cover crop.
Per 100 g edible portion of immature pods contain: water 82.4 g, protein 4.5 g, fat 0.1 g, carbohydrates 10.0 g, fibre 2.0 g, ash 1.0 g. The energy content averages 1260 kJ/100 g. The content of protein in mature seeds is normally 21-29 g/100 g. Fully ripe Indian seeds contain per 100 g edible portion: water 9.6 g, protein 24.9 g, fat 0.8 g, carbohydrates 60.1 g, fibre 1.4 g, ash 3.2 g. The energy content averages 1403 kJ/100 g. The presence of a cyanogenic glycoside has been reported in certain cultivars. Seed weight varies between 25 and 50 g/100 seeds.
- A bushy or a climbing and branching, pubescent herbaceous perennial, often grown as an annual, up to 6 m tall, with a well developed tap-root with many laterals and well developed adventitious roots.
- Leaves alternate, trifoliolate; leaflets broadly ovate, 5-15 cm × 4-15 cm, entire, subglabrous or soft hairy.
- Inflorescences stiff axillary racemes with many flowers; peduncle 4-23 cm long, often compressed, glabrescent; rachis 2-24 cm long; flowers arising 1-5 together from tubercles on rachis
- Pedicels short, square, sparsely pubescent; flowers white, pink, red or purple; stamens diadelphous (9 + 1); ovary sessile, ca. 10 mm long, finely pubescent; style abruptly upturned, 8 mm long; stigma capitate, glandular.
- Pods variable in shape and colour, flat or inflated, 5-20 cm × 1-5 cm, straight or curved, usually with 3-6 ovoid seeds of varying colour and size.
Growth and development
Germination is epigeal and normally takes 5 days. Seed remains viable for 2-3 years and has an average germination rate of 85-95%. Growth period varies from 75 to 300 days. Improved cultivars start fruiting 60-65 days after sowing and continue for 90-100 days. Early-maturing cultivars that can be grown all year round produce pods 60 days after sowing and continue up to 120 days. Mature seeds are harvested 150-210 days after sowing, depending upon cultivar and time of sowing. In India, short-day cultivars start flowering 42-330 days after sowing, depending on the sowing date. The flowers are mainly cross-pollinated.
Other botanical information
The variability of lablab is great; many cultivars exist. Many subclassifications of the species can be found in the literature. Some distinguish subspecies, others varieties. For cultivated plants, the distinction of cultivar (cv.) groups seems most appropriate.
- Cv. group Lablab (widely distributed): mature seeds with the long axis at right angles to the suture; pods dehiscent or indehiscent; seeds not longer than 1/3 - 3/4 of the width of the mature pod;
- Cv. group Ensiformis (South-East Asia, East Africa): mature seeds with long axis more or less oblique to the suture, nearly filling the mature pod; pods indehiscent; when young, difficult to distinguish from cv. group Lablab;
- Cv. group Bengalensis (South Asia, East Africa): mature seeds with long axis parallel to the suture, more or less filling the mature pod, gibbous dorsally and at base; pods indehiscent.
Lablab is a short-day plant. It requires high temperatures to grow well (18-30 °C). Minimum temperature for growth is 3 °C. Its frost tolerance is low; light frosts damage the leaves but do not kill the plants. It prefers rainfall at 750-2500 mm/year. Once established (2-3 months after sowing), lablab is quite drought-tolerant. It has a deep root system which can make use of residual soil moisture. It is reported to grow in areas with rainfall at 200-2500 mm/year. Plants do not tolerate standing brackish water or waterlogging. In India and Burma, the plants are often grown on exposed sandy river banks. Provided drainage is good, the plant is extremely tolerant of soil texture, growing in deep sands to heavy clays, pH ranging from 5-7.8. Lablab prefers the lower altitudes but is grown as a dry-land crop up to 2000 m in the tropics.
Propagation is by seed at 7-10 kg/ha, up to 5 cm deep in a preferably well prepared seed-bed. Lablab can establish itself after being broadcast into roughly ploughed land, if the seed is covered to some extent. As a field crop, lablab is usually sown in rows, either as a sole crop (rows 1 m apart) or intercropped with a cereal, e.g. with maize, rows 80 cm apart. In India, it is invariably grown with Eleusine coracana. Inoculation with cowpea-type Rhizobium strains is advised, if lablab has not been grown recently. Lablab is only grown by smallholders.
Weed control during the early stages of growth may be necessary. Recently the use of pre-emergence herbicides such as chloramben, chlorthal dephenamid, trifluralin and dinoseb has been suggested. Generally no fertilizer is applied on fertile soils. In poor sandy soils, molybdenized superphosphate at 250-500 kg/ha and some potash is advised. In India, garden cultivars are heavily manured, frequently irrigated and supported for climbing. They are sown in pits and thinned to 4 vines after 1 month. Lablab is sometimes grown as a cover crop in rotation with sorghum and cotton. In orchards, lablab forms a good organic mulch when cut often. It can also produce a good yield of hay, which is easily cured through its low moisture content. It also produces good silage, especially when mixed with sorghum.
Diseases and pests
Pod-boring larvae are the most serious pests of the lablab bean. Adisura atkinsoni is particularly troublesome. That pest has been controlled experimentally by strain HB-III of Bacterium cereus var. thuringensis. In addition, the gram caterpillar, Heliothis armigera, the plume moth, Exelastis atomosa, and the spotted podborer, Maruca testulalis, are of considerable economic significance. Insect infestation during storage is particularly caused by bruchid beetles, Callosobruchus spp., which also attack the crop in the field. Anthracnose, caused by Colletotrichum lindemuthianum, can cause serious crop losses; spraying with zineb or captan is reported to give reasonable control. Leaf-spot, caused by Cercospora dolichi, and powdery mildew, Leveillula taurica var. macrospora, may also be troublesome and are controlled by spraying with Bordeaux mixture.
The green pods are picked by hand when they have reached a reasonable size, usually when the seeds are three-quarters ripe. They are generally picked from the plants at intervals of 3-4 days, cleaned and graded for size, before being packed in baskets for the market. In many cultivars, the pods mature in succession on the stem and shatter once they are ripe. For seed production, the pods are frequently picked by hand as soon as they ripe, until the plants reach full maturity and the major proportion of the remaining pods has ripened. At that stage, the entire plant is cut close to the ground with a sickle and the vines left to dry for a few days before threshing.
The average yield of green pods is 2600-4500 kg/ha, and of seed is 450 kg/ha if grown as intercrop and up to 1460 kg/ha in sole cropping. Fodder yields are 25-40 t/ha.
Handling after harvest
Storage at 0-2 °C and a relative humidity of 85-90 % is reported to extend the shelf-life of the green pods to a maximum of 21 days and of the shelled fresh beans up to 7 days. After drying and cleaning, mature seeds are stored; usually earthenware or metallic containers are used in South-East Asia, and the seeds may be covered with a 5-cm protective layer of sand. Harvesting pods as soon as the seed is ripe reduces bruchid infestation; reduction of the moisture content to below 10 % is more effective.
There is wide genetic variation in the tropics and subtropics. More than 250 lines, both indigenous and exotic, are maintained and catalogued at the University of Agricultural Sciences of Bangalore, India. Small collections are available at TNAU (Tamil Nadu Agricultural University), Coimbatore and IIHR (Indian Institute of Horticultural Research), Bangalore. No attempts have been made so far to collect and catalogue the germplasm elsewhere in the world. In Australia and New Zealand, only fodder types are maintained.
Most of the improvement work is concentrated in India. The local landraces are of long duration, photosensitive and low-yielding (500-600 kg/ha). The main breeding objective is higher yield. With germplasm collections, India is trying to obtain bushy short-duration day-neutral disease-resistant cultivars.
As well as being a pulse, lablab is becoming more relevant for green manure, as a cover crop, for pasture and for fodder. Its drought resistance and its suitability for all types of soils gives it a wide range of options. Research priorities are: collection of all cultivars (germplasm); identification of suitable Rhizobium strains; investigation of its value as an intercrop with food and forage crops; further evaluation of the nutritional value of the seeds for man and animal.
- Duke, J.A., 1981. Handbook of legumes of world economic importance. Plenum Press, New York and London. pp. 102-106.
- Shivashankar, G., Vishwanatha, S.R., Manjunath, A. & Chandrappa, H.M., 1971. Inheritance studies and breeding in Dolichos. Proceedings of the International Symposium on Subtropical and Tropical Horticulture, February 1972. Bangalore, India.
- Skerman, P.J., 1977. Tropical forage legumes. FAO, Rome. Plant Production and Protection Series No 2. pp. 314-322.
- von Schaaffhausen, R., 1963. Dolichos lablab or hyacinth bean: its uses for feed, food and soil improvement. Economic Botany 17:146-153.
- G. Shivashankar & R.S. Kulkarni
Source of This Article
Shivashankar, G. & R.S. Kulkarni, 1989. Lablab purpureus L. (Sweet)In: van der Maesen, L.J.G. & Somaatmadja, S. (Editors). Plant Resources of South-East Asia No. 1: Pulses. Pudoc, Wageningen, The Netherlands, pp. 48-50
Shivashankar, G. & R.S. Kulkarni, 1989. Lablab purpureus L. (Sweet)In: van der Maesen, L.J.G. & Somaatmadja, S. (Editors). PROSEA (Plant Resources of South-East Asia) Foundation, Bogor, Indonesia.