Macrotyloma uniflorum (horsegram, also known as horse gram, kulthi bean, gahat, hurali, or Madras gram) is a legume native to tropical southern Asia. Known for its distinct taste and texture, its rich nutrients and reputed medicinal properties, it is widely used in many cuisines. It is also commonly grown for horse feed, hence the name "horse gram". Horse gram is grown in parts of India, Nepal, Malaysia, Sri Lanka, and the West Indies. Consumed whole, sprouted, or ground, it is also allowed to be eaten on some Hindu fasting days. Medical uses of these legumes are described in the Ayurveda.

Description

Macrotyloma uniflorum is a perennial climbing plant with a rhizome, growing to a height of about . The stem sprouts from the rhizome each year. It is clad in varying amounts of whitish hairs and bears alternate, trifoliate leaves with petioles up to long. The leaflets are obovate or elliptical, and up to long. The flowers are borne in twos or threes in the leaf axils, and are typical of the bean family with banner, wings and keel. They are cream, yellowish or green, often with a purple blotch inside. These are followed by linear-oblong, upcurving pods up to long, containing up to ten reddish-brown, speckled or black seeds.

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File:Macrotyloma Uniflorum young plant 01.jpg|Young plant

File:Macrotyloma Uniflorum flower 01.jpg|Flowers

File:Macrotyloma Uniflorum fruit 01.jpg|Young fruit

File:Macrotyloma Uniflorum dissected flower 01.jpg|Dissection of floral parts

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Distribution

Horse gram is native to tropical southern Asia and has been found in archaeological sites in India, starting from 2500 BC. The plant was probably first domesticated in India, and is now grown as a legume from India to Myanmar. Additionally, the crop is also grown for fodder and green manure in tropical countries in southeastern Asia and northern Australia. Generally, the major growing areas of Macrotyloma uniflorum are located in India, Africa and Australia.

Cultivation

Horse gram is drought tolerant and also withstands harsh environmental conditions such as salinity or metal stresses. Generally, Horse Gram is planted with low agronomic inputs and without weeding. Furthermore, the crop grows on a broad range of soil types with different pH ranges. Cultivation is also possible on soils with poor organic matter and nitrogen availability.

The plant is not only cultivated as a monoculture, but also as an inter- or mixed crop together with groundnut, sorghum, sesame, Niger, maize, finger millet, pearl millet, amaranth, marvel grass or kidney bean. Furthermore, Macrotyloma uniflorum can also be grown along with trees such as neem, white siris or babul. Both, grain and green forage yield are highly dependent on the growing region as well as the selected cropping system. Substantial yield differences in the various growing regions exist: In India green forage yield varies from 5 - 14 t/ha and in Australia approximately 4.4 t/ha are reported. Grain yield in India is around 0.13 – 1.2 t/ha and 1.1 – 2.2 t/ha in Australia.

Pests

Yield-impacting diseases are anthracnose (Colletotrichum lindemuthianum), the yellow mosaic virus as well as powdery mildew. Other diseases affecting horse gram are dry root rot (Macrophomina phaseolina), rusts, aerial blight (Rhizoctonia solani) and leaf spot (Cercospora). The pod borer (Etiella zinckenella) and the pod fly (Melanagromyza obtusa) are the most damaging insect pests.

Horse gram seed contains carbohydrate (57.2% w/w), protein (22% w/w), dietary fiber (5.3% w/w), fat (0.50% w/w), calcium (287&nbsp;mg), phosphorus (311&nbsp;mg), iron (6.77&nbsp;mg) and calories (321 kcal) as well as vitamins like thiamine (0.4&nbsp;mg), riboflavin (0.2&nbsp;mg) and niacin (1.5&nbsp;mg) per 100 grams of dry matter. The nutritional content is partly dependent on soil conditions and the weather. The less appealing taste has led it to be not commonly eaten.

The carbohydrate-fraction of horse gram flour consists of oligo-saccharides and starches. The starches can be divided in terms of digestability in those that can be digested and uptaken in the small intestine, and those that partly will fermented in the colon by the microflora. The latter ones, called resistant starches, account for 43.4% of the carbohydrate content of horse gram flour. Oligo-saccharides such as raffinose and stachyose contribute to digestion difficulties. The fermentation in the colon often may lead to flatulence and diarrhoea, given the high concentration of both, resistant starches and oligo-saccharides, for horse gram longer cooking times, and other treatments are needed.

Breeding

Globally, southwest India and the African continent are regarded as horse gram gene-rich regions. The US Department of Agriculture's (USDA) Germplasm Resources Information Network (GRIN) has preserved 35 accessions of horse gram, the Australian Tropical Crops and Forages Genetic Resources Centre, has 38 accessions and the Kenya Agricultural Research Institute (KARI) has conserved 21 accessions. Many unfavorable traits such as late flowering, indeterminate twining growth habit, long and thin stem, thermo- and photosensitivity and a poor harvest index exist in horse gram.

  • In Darjeeling and Sikkim, horse gram called गहत (gahat) in Nepali is considered a medicinal food. It is given to children suffering from mumps. Water in which gahat is soaked is taken by people suffering from kidney stones in the belief that this dissolves the crystals. Gahat's use is specially reserved for the cold winters, when its heat-producing properties are most useful.
  • In Kerala, horse gram, called മുതിര (muthira) in Malayalam is used in special kinds of dishes.
  • In Tamil Nadu, horse gram, called கொள்ளு (kollu) in northern districts and காணம் (kaanam) in southern districts is commonly used in Tamil dishes, including kollu chutney, ', kollu avial, kollu sambar and kollu rasam.
  • In Maharashtra and Goa, horse gram is called हुलगा/हुलगे/कुलीथ (hulage/hulaga/kulith) in Marathi and कुुली (kulith) in Konkani is often used to make ' and shengule/shevanti
  • In Karnataka cuisine, ಹುರಳಿಸಾರು (huraḷi saaru) is more popular, because of ಹುರಳಿ (huraḷi) is a main ingredient. Huraḷi is also used in preparations such as usali, chutney, bassaru, and upsaaru or upinsaru (particularly in the Old Mysore Regions Mandya and Chamrajnagara Districts).
  • In South Canara region of Karnataka, in Tulu, it is also called kudu (ಕುಡು).
  • In Odisha it is known by the name କୋଳଥ (Koḷatha).
  • Gahat or kulath is a major ingredient in the food of Pahari region of northern India.
  • In Himachal Pradesh, kulath is used to make khichdi. In Uttarakhand, it is cooked in a round iron saute pan (kadhai) to prepare ras, a favorite of most Kumaonis. In Garhwal region, another more elaborate dish is phanu which is made in a kadhai with roughly ground gahat (previously soaked overnight) boiled over several hours. Towards the end, some finely chopped greens (palak or spinach, rai, tender radish leaves, or dhania (coriander leaves) if nothing else is available) are added to complete the dish. Served with boiled rice, ' (a millet-like grain, used as a staple by poorer Garhwalis only a decade ago and now a prized health-food).

In Myanmar (Burma), horse gram is known as pe bazat () in Burmese. It is commonly used in making pon ye gyi, a fermented bean paste used in traditional Burmese cuisine.

References