Vigna radiata (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Vigna radiata (L.) Wilczek

Protologue: Flore du Congo Belge et du Ruanda-Urundi 6:386 (1954).
Family: Leguminosae
Chromosome number: 2n= 22

Synonyms

  • Phaseolus radiatus L. (1753),
  • Phaseolus aureus Roxb. (1832).

Vernacular names

  • Mungbean, green gram, golden gram (En)
  • haricot mungo, haricot doré (Fr)
  • Burma: pè-di-sien
  • Indonesia: kacang hijau, arta ijo
  • Malaysia: kacang hijau
  • Philippines: mongo, balatong
  • Thailand: thua khieo, thua thong
  • Vietnam: dâu xanh, dâu chè
  • Cambodia: sândaèk ba:y
  • Laos: thwàx khiêw, thwàx ngo:k, thwàx sadê:k.

Origin and geographic distribution

Mungbean originated in India or the Indo-Burmese region where it has been cultivated for several millenaries. It spread in early times to most other Asian countries, and more recently also to other continents. In spite of its present wide distribution, mungbean never became a major commercial crop outside Asia. In most South-East Asian countries, mungbean ranks among the three most important grain legumes.

Uses

The dried beans are prepared by cooking or milling. They are eaten whole or split (dhal). The seeds or the flour may enter in a variety of dishes like soups, porridge, snacks, bread, noodles and even ice-cream. Mungbean starch is extensively used for starch noodles, mungbean protein for fortifying cereal flours. Both fractions can be separated by air-classification. Most popular as a fresh vegetable in oriental cooking are sprouted mungbean seeds. Crop residues are an important fodder. Mungbean is sometimes specifically grown for hay, green manure or cover crop.

Production and international trade

World mungbean production in the eighties is estimated to be around 2 million t from 4 million ha. India is by far the most important producer (1.2 million t from 2.8 million ha), followed by Thailand (0.25 million t from 0.4 million ha) and Indonesia (0.20 million t from 0.3 million ha). With mungbean loosing its image as 'poor man's meat' due to high market prices, there is ample scope for increased production to meet the growing domestic demand in most South-East Asian countries. In Indonesia, harvested area doubled and domestic production tripled in the period 1975-1985. International trade is dominated by Thailand, which exports about half of its annual production of 250 000 t, mainly to Japan, Taiwan, Philippines, Malaysia and Singapore, but also to Europe and USA.

Properties

Mungbean has better digestibility and lower production of flatulence than most other pulses, making it suitable for children and older people. Dry mungbean seeds have, per 100 g edible portion, an energetic value of 1430 kJ, and contain water 10 g, protein 22 g, fat 1 g, carbohydrates 60 g, fibre 4 g and ash 3 g. Variation in protein content (17-26%) is more influenced by environment than by genotype. Mungbean protein is deficient in methionine and cystine, but has high lysine values, making it an excellent complement to rice. Mungbean seeds are a good source of minerals, provitamine A and vitamine B complex, while bean sprouts are in addition rich in ascorbic acid (vitamine C). Mungbean is low in antinutritional factors. Heating and sprouting denatures growth inhibitors. Seed weight varies between 1.5 and 8.5 g/100 seeds.

Description

  • An erect or semi-erect, sometimes twining, herbaceous annual, 25-130 cm tall. Branching starts from lower and intermediate nodes (rarely from cotyledons or unifoliolate leaves).
  • First two leaves opposite and simple, subsequent leaves alternate and trifoliolate; leaflets ovate to deltoid, 5-18 cm x 4-15 cm, usually entire.
  • Flowers are large, 1-2 cm in diameter, greenish to bright yellow, self-fertile, borne in clusters of 5- 25 on axillary racemes, 2-20 cm long.
  • Pods spreading and pendent, cylindrical, up to 15 cm long, usually straight, pubescent or glabrous, black or tawny brown, with up to 20 globose to ellipsoid seeds.
  • Seeds green or yellow, occasionally brown or blackish, with dull or glossy lustre (associated with pod wall remnants); hilum flat and white. Germination is epigeal.

Growth and development

Mungbean is a short duration crop, usually flowering within 30-70 days after sowing and maturing within 60-120 days. Flower abscission is prevalent and may reach 90%. Mungbean is usually determinate, but because the inflorescences remain meristematic and may redevelop flowers after a period of adverse conditions, it flowers and fruits over a period of several weeks. Green leaves, open flowers, green pods and ripe pods occur simultaneously on the same plant. A large part of the dry matter accumulated during seed-filling may still be partitioned to vegetative plant parts. For this reason, rapid senescence (shedding of the leaves uniformly from the plant) does not occur. Although self-pollination is the rule and cleistogamy common, outcrossing up to 5% may occur. Pollination usually takes place during the night, before the flowers open early in the morning. It takes 3-4 weeks from flower opening to mature pod.

Other botanical information

Mungbean is morphologically very similar to black gram (Vigna mungo (L.) Hepper) and they are sometimes considered variants of the same species. Chemotaxonomy and cytogenetics, however, support the distinction, but the debate still continues. Both species are sometimes considered to be domesticates from the same wild forms (Vigna sublobata, based on Phaseolus sublobatus Roxb.). Nowadays, the cultivated forms of mungbean are usually grouped as V. radiata var. radiata, although a classification into cultivar groups would be more appropriate. The wild forms are usually classified into two botanical varieties: var. sublobata (Roxb.) Verdc. and var. setulosa (Dalzell) Ohwi & Ohashi.

Var. sublobata is smaller in all parts compared to var. radiata, and occurs in India, Sri Lanka, S.-E. Asia, Queensland, Madagascar and East Africa. Var. setulosa has large, almost orbicular stipules and dense long hairs on the stem. It occurs in India, China, Japan and Indonesia.

Ecology

Mungbean is a 'short-day' plant. Cultivars differ markedly in sensitivity, but most genotypes show quantitative short-day responses, flower initiation being delayed by increases in the length of the photoperiod. Qualitative responses (no flower initiation if photoperiod longer than a certain critical value) occur, while absolute day neutrality has yet to be confirmed. Mungbean is a 'warm season' crop and will grow within a mean temperature range of about 20-40 °C, the optimum being 28- 30 °C. It can therefore be grown in summer and autumn in warm temperate and subtropical regions and at altitudes below 2000 m in the tropics. The crop is very susceptible to waterlogging, but withstands drought stress relatively well, by curtailing the period from flowering to maturity. Water requirement is about 200-300 mm per growing season. The crop does best on well-drained loam or sandy loam, with pH 5.5-7.0. There is little information on tolerance to aluminium toxicity. Mungbean nodulates readily withRhizobiumstrains from the cowpea cross-inoculation group. Because these strains are rather common, there is little response to inoculation.

Propagation

Propagation is by seed. There is no seed dormancy (sprouting in the pod may occur under very humid conditions). Sowing is by broadcasting or dibbling in individual hills or in rows. Mungbean is grown mainly on small holdings, often as mixed or intercrops. Associated crops are usually of longer duration than the mungbean (sugarcane, cotton, sorghum), but sometimes of shorter duration (Madura maize, Indonesia). To make use of a short cropping period, short duration mungbean is often relay-cropped.

Husbandry

In the major area of cultivation, the monsoon tropics, mungbean is mainly grown as rainy season crop on dryland or as dry season (post-monsoon) crop in rice-based systems on wetland, making use of residual moisture and/or supplementary irrigation. In some areas, where adequate early rains occur, an early season (pre-monsoon) crop can be grown. With the newer 60-75 days cultivars, maximum yields are obtained at densities of about 300 000-400 000 plants/ha. The later maturing traditional cultivars generally need wider spacing. Usually no fertilizers are applied to mungbean. It utilizes residues from applications to the main crops in the system, although it responds well to phosphate applied at rates of 20-80 kg P2O5/ha. 1 t dry seed corresponds to a nutrient removal of 40 kg N, 4 kg P, 12 kg K, 1 kg Ca, 2 kg S and 2 kg Mg. The loss is usually much higher due to the use of crop residues for fodder. Over the centuries, mungbean's adaptation to stable performance in marginal environments, has resulted in a low yield potential, which limits responsiveness to better environments and improved cultural practices.

Diseases and pests

Most serious fungal diseases are leaf spot (Cercospora canescens) and powdery mildew (Erysiphe polygoni) and to a lesser degree scab (Elsinoe iwatae), anthracnose (Colletotrichum lindemuthianum) and rust (Uromyces spp.). Important bacterial diseases are blights caused by Xanthomonas and Pseudomonas. Mungbean suffers from several virus diseases, but with the exception of Mungbean Yellow Mosaic Virus (MYMV), they are not very well described. Beanflies (Ophiomyia phaseoli and related species) can cause serious stand reductions at the seedling stage, while much economic damage is done by pod-borers (Heliothis spp., Etiella zinckenella, Maruca testulalis) and pod-suckers as the green stink bug (Nezara viridula). An important storage insect is the seed weevil (Callosobruchus spp.), which destroys the whole seed-lot if uninterrupted.

Harvesting

Generally by 2-5 hand pickings at weekly intervals. Harvesting is the most expensive single operation in mungbean growing. Short duration cultivars, which ripen more uniformly, may be processed as whole plants on small rice threshers. Cultivars differ markedly in harvesting efficiency, depending on position (above or within canopy) and size of pods.

Yield

Yields per hectare (monocropping) are low and vary from about 300-700 kg/ha in the major producing countries. Experimental yields larger than 3 t/ha have been realized.

Handling after harvest

Hand-picked pods are dried in the sun. Spontaneous shattering can be speeded up by beating with a stick or by trampling. Seed cleaning is done by screening and winnowing. Properly dried, mungbean seed maintains high viability over a long period. Sowing seed, stored by small farmers, is often of poor quality due to bruchid damage. For long term storage and overseas shipments, seeds are usually fumigated.

Genetic resources

Holders of the largest germplasm collections are AVRDC, Shanhua, in Taiwan (6000 accessions), USDA, Georgia and Colorado, in USA (3500), Punjab Agricultural University, Ludhiana, in India (3000), and CAAS, Beijing, China (3000). Several smaller but important collections exist at research institutes in the South-East Asian countries: FCRI (Bangkok) in Thailand, BORIF (Bogor) and MARIF (Malang) in Indonesia, IPB (Los Banos) in the Philippines. Internationally, the emphasis is at present on evaluation and documentation work to improve user's access to the collections.

Breeding

In many traditional mungbean growing areas, farmers still grow old landraces, mixtures of homozygous genotypes, very well equipped to adjust to changing environmental conditions, giving stable, but seldom excellent, yields. Even recently, many cultivars have been developed from these landraces by simple pure-line selection: identification of the outstanding genotypes in these mixtures. These well-adapted local selections form an excellent starting-point for hybridization programmes. Nowadays, the breeding challenge is to overcome the genetic limitations deriving from centuries-long adaptation of mungbean to marginal environments. The traditional, late, robust plant types have been replaced by new types useful for short seasons and multiple cropping systems with mungbean occupying the land for short periods between major crops. These are short, compact plants with high harvest index, with reduced photoperiod sensitivity, and with a more uniform maturity. Many modern cultivars have already been released in the major producing countries, which also have improved resistance to major pests and diseases. Sources of resistance have been identified in germplasm of mungbean and related species. Black gram (Vigna mungo) shows, among the Asiatic Vigna species, most promise for interspecific hybridization with mungbean. At present, little attention is given to protein content and quality, because much more impact on total protein production is to be expected from increasing yields.

Prospects

Demand for food legumes will continue to grow. Short duration mungbean is very suitable to increase the cropping intensity of agricultural land. New developments in food technology make expansion of mungbean utilization possible. Bean sprouts are gaining popularity as a winter vegetable in many temperate areas. Production research should focus on reliable yield and good seed quality (weathering resistance). Processing research should focus on diversification and quality of mungbean products.

Literature

  • AVRDC. Progress Report Summaries 1979-1986, AVRDC, Taiwan.
  • AVRDC, 1988. Proceedings of the Second International Mungbean Symposium. AVRDC, Taiwan (in press).
  • Cowell, R. (Editor), 1978. Proceedings of the First International Mungbean Symposium. AVRDC, Taiwan. 262 pp.
  • Lawn, R.J. & Ahn, C.S., 1985. Mung bean (Vigna radiata (L.) Wilczek/Vigna mungo (L.) Hepper). In: Summerfield, R.J. & Roberts, E.H. (Editors): Grain legume crops. Collins, London. p. 584-623.
  • Morton, J.F., Smith, R.E. & Poehlman, J.M., 1982. The Mungbean. Special publication of the College of Agricultural Sciences, Department of Agronomy and Soils, University of Puerto Rico, Mayaguez. 136 pp.
  • Kay, D.E., 1979. Food Legumes. Crop and Product Digest No. 3 - Tropical Products Institute, London, p. 273-292.

Authors

  • J.S.Siemonsma & Arwooth Na Lampang