The Guar or cluster bean (Cyamopsis tetragonoloba) is an annual legume and the source of guar gum. It is also known as Gavar, Guwar or Guvar bean.
The origin of Cyamopsis tetragonoloba is unknown, since it has never been found in the wild. It is assumed to have developed from the African species C. senegalesis. It was further domesticated in India and Pakistan, where it has been cultivated for many centuries. Guar grows well in arid to semiarid areas, but frequent rainfall is necessary. This legume is a very valuable plant within a crop rotation cycle, as it lives in symbiosis with nitrogen-fixing bacteria. In fact, agriculturists in semi-arid regions of Rajasthan follow crop-rotation and use Guar as a source to replenish the soil with essetial fertilizers and nitrogen fixation, before the next crop. Guar as a plant has a multitude of different functions for human and animal nutrition but its gelling agent containing seeds (guar gum) are today the most important use. Demand is rising rapidly due to industrial use of guar gum in hydraulic fracturing (oil shale gas). About 80% of world production occurs in India and Pakistan, but, due to strong demand, the plant is being introduced into new areas.
Guar is very drought-tolerant and sun-loving, but it is very susceptible to frost. Even though it can cope with little but regular rainfall, it requires sufficient soil moisture before planting and during maturation of seeds. Frequent drought periods can lead to delayed maturation. On the contrary, too much moisture during early phase of growth and after maturation lead to lower seed quality.
Cyamopsis tetragonoloba (L.) can grow on a wide range of different soil types. Preferably in fertile, medium-textured and sandy loam soils that are well-drained because waterlogging decreases plant performance. In respect of soil acidity, guar grows best in moderate alkaline conditions (pH 7-8) and is tolerant of salinity. Thanks to its taproots which are inoculated with rhizobia nodules, it produces nitrogen-rich biomass and improves soil quality
It is grown principally in north-western India and Pakistan with smaller crops grown in the semiarid areas of the high plains of Texas in the USA, Australia and Africa. The most important growing area centres on Jodhpur in Rajasthan, India where demand for guar for fractionation produced an agricultural boom as in 2012. Currently, India and Pakistan are the main producers of cluster bean, accounting for 80% production of the world’s total, while Thar, Punjab Dry Areas in Pakistan and Rajasthan occupies the largest area (82.1%) under guar cultivation in India. In addition to its cultivation in India and Pakistan, the crop is also grown as a cash crop in other parts of the world (Pathak et al. 2010). Several commercial growers have converted their crops to guar production to support the increasing demand for guar and other organic crops in the United States.
• Forage: Guar plants can be used as cattle feed, but due to hydrocyanic acid in its beans, only mature beans can be used.
• Green manure: Guar plantings increase the yield of subsequent crops as this legume conserves soil nutrient content.
• Vegetable: Guar leaves can be used like spinach and the pods are prepared like salad or vegetables. Its beans are very nutritious but the guar protein is not usable by humans unless toasted to destroy the trypsin inhibitor.
As mentioned in the biology part of this entry, the seeds of the guar bean contain a very big endosperm. This endosperm consists of a very big polysaccharide of galactose and mannose. This polymer is water soluble and exhibits a viscosifying effect in water. Guar gum has a multitude of different applications:
Guar is very useful item for alternative fuel.