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, widely used legume in many cuisines. It is also known for human consumption for its rich nutrients and reputed medicinal properties. It is commonly grown for horse feed, hence the name “horse gram”. Horse gram grown in parts of India, as well as Nepal, Malaysia, Sri Lanka, and is introduced to the West Indies. It is consumed whole, sprouted, or ground. It is consumed in many parts of India and is also known as a superfood, as many Hindus use them to gain nutrients that is not normally found in their sattvic (vegetarian) diet. Horse gram is also allowed to be eaten on some Hindu fasting days. Medical uses of these legumes have been discussed and is 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. The seeds have a length of .
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 in 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. Horse gram thrives where the temperature is in the range of . Frost temperatures are lethal. Due to the drought-resistance Macrotyloma uniflorum is grown in areas with low precipitation (). In wetter areas, Horse gram is usually sown at the end of the rainy season to still facilitate cultivation. Nonetheless, Macrotyloma uniflorum does not tolerate waterlogging.
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 dieseases 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. Others are aphids (Aphis craccivora), hairy caterpillar (Azazia rubicans), pod caterpillar (Helicoverpa armigera), American serpentine leaf miner (Liriomyza trifolii), thrips, leaf hoppers and Callosobruchus as a storage pest.