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Phaseolus aconitifolius Jacq.
Vigna aconitifolia or mat bean is a drought resistant legume, commonly grown in arid and semi-arid regions of India. It is commonly called mat, moth, matki or dew bean. The pods, sprouts and protein rich seeds of this crop are commonly consumed in India. Moth bean can be grown on many soil types, and can also act as a pasture legume.
Moth bean is an herbaceous creeping annual which grows to approximately 40 cm high. Yellow flowers on its hairy and densely packed branches develop into yellow-brown pods, 2 to 3 inches in length The seeds of these pods contain approximately 22–24% protein.
Due to its drought resistant qualities, its ability to combat soil erosion and its high protein content, moth bean has been identified as possibly a more significant food source in the future. It has been suggested that its suitability as a grain legume in semi-arid Africa should be further investigated.
Belonging to the family Fabaceae (sub-family Faboideae), the moth bean is an herbaceous creeping annual that creates a low-lying soil cover when fully grown. Its stem can grow up to 40 cm in height, with its hairy and dense-packed branches reaching a span of up to 150 cm. Yellow flowers develop into a brown pod 2.5 to 5 cm in length, which holds 4 to 9 seeds inside. The rectangular seeds exist in a variety of colours including, yellow-brown, whitish green and mottled with black.
History and geography
Moth bean is native to India and Pakistan, grown for food production and as a forage and cover crop. It is predominately grown in India, although it has been cultivated in the United States, Australia, Thailand and other parts of Asia. 1.5 million hectares of land is used in India for moth bean production, producing approximately 0.4 million t/ha of seeds  While its presence in Sudan, Somalia and other tropical countries of Africa has been noted, it has not been a crop of great importance to this region. The potential of increased production in this region in the future has been suggested.
Moth bean, a short-day crop, is one of the most drought resistant pulses in India. Grown at altitudes up to 1300m above sea level, it has a wide pH range (3.5–10) and can tolerate slight salinity. While dry sandy soil is most suitable for production, moth bean can tolerate a variety of soil types. The low lying soil cover the crop creates helps prevent soil erosion by preventing moisture loss.
Optimum production of moth bean occurs between 24–32 °C, but has been shown to tolerate up to 45 °C during the day. Growth is optimal at a constant temperature. The moth bean is one of the most drought resistant pulse in India, requiring little irrigation for production. While optimal annual rainfall for production is 500–750 mm, it is able to grow with 200–300 mm annually, and some yield has been noted at rainfall levels as low as 50–60 mm per year. Propagation of moth bean is done by seed, preferably on a prepared seedbed, at an optimal temperature of 25–27 °C. Fertilizer applications to moth bean are uncommon in India.
Other farming issues
Moth bean is grown for both human consumption and as a forage crop. Currently in India, moth bean is grown on its own or intercropped with other cereals, such as pearl millet. It is also grown in rotation with cotton as a forage crop. When grown as a forage crop, it is planted 7–34 kg/ha, and 10–20 kg/ha when grown as the only crop. Row planting should be done 30–90 cm apart, with seeds sown 2.5–4 cm deep. It takes 75–90 days for moth bean to mature, and is frequently planted at the end of the rainy season.
A drawback to this crop is its difficulty to harvest. Mowers cannot be used due to the shape and density of the moth bean’s branches, so the crop is typically cut with a sickle. It is threshed and winnowed after being dried for approximately one week. Hay yields from this crop are 7.5-10 t/ha, while forage matter yields range from 37-50 t/ha. Seed yields are currently low, ranging from 70–270 kg/ha. However, research shows that this crop has the potential to increase in yield. Experimental seed yields of up to 2600 kg/ha have been recorded in the US and Australia.
Major pests and diseases
Moth bean is impacted by Mung Bean Yellow Mosaic Virus (MYMV), for which Bemisia tabaci is the vector. Root rot and seedling blight from Macrophomina phaseolina also causes damage, as well as some Striga species and the nematode Meloidoigyne incognita Meloidoigyne incognita. There are some resistant cultivars to these pests and diseases.
Little breeding work has been completed on the moth bean, but researchers have found that there is substantial genetic variation between moth bean germplasms. The National Bureau of Plant Genetic resources in New Delhi, India, houses more than 1000 accessions. Some improved cultivars such as ‘RMO-40’ and ‘RMO-225’are available in India.
Whole or split moth bean seeds can be cooked or fried. In India, the seeds are traditionally consumed for breakfast, after being sprouted and cooked. Fried splits make up a ready-to-eat product in India called dalia  and can be used to make traditional dahl. The moth bean pods can be boiled and eaten, and seeds can be ground into flour. It is believed that consumption of the seeds can help treat a fever. Moth bean is also consumed as a forage crop by animals.
100g of raw, uncooked moth bean seeds contain 343 calories, 23 g of protein, 62 g of carbohydrate and 1.6 g of fat. As is the case with other legumes, this pulse does contain antinutritional factors that limit available protein. However, research has shown that the Moth bean contains considerably less of these factors compared with other legume grains, making it a more beneficial choice for consumption. Soaking and cooking moth beans before consumption helps to break down antinutritonal factors and makes the protein more digestible.
Constraints to wider adaptation
While its drought tolerance and high protein content could make moth bean a potential crop choice for semi-arid Africa, a lack of management knowledge and the difficulty of harvest due to its density and creeping nature could make its spread to other parts of the world difficult. Further research into more
Cultivation information of this crop is limited. Some of the most in-depth information on moth bean is available from the Plant Resources for Tropical Africa website http://www.prota.org. Additional information, including a farm case study, can be found at the website of the Indian Council for Agricultural Research http://www.icar.org.in/en/node/680.
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- U.S. Department of Agriculture, Agricultural Research Service. 2013. USDA National Nutrient Database for Standard Reference, Release 26. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl