Tepary bean (Phaseolus acutifolius) is a legume crop that originated in the southwestern United States and central Mexico and is grown as far south as El Salvador. Although tepary bean was once widely used in the Sonoran Desert and other arid regions of North America, its production declined as a result of the development of modern, mechanized irrigation techniques after World War II that enabled a shift to other crops. Today, most tepary bean is produced by subsistence farmers for household consumption but wider use of this crop has potential to support climate change adaptation of Mesoamerican farm systems.
Tepary bean is more drought tolerant than other types of beans, and may grow in areas with as little as 40-170 cm of annual rainfall. Drought tolerance is owed to its deep root system, which also enables resistance to soil salinity. In dry areas where water is now declining, farmers are able to use traditional floodwater management methods such as catchment basins and construction of canals to grow tepary bean.
Tepary bean has a rich, nutty taste and is an excellent source of fibre, carbohydrates, and protein. It has similar energy, protein, fat and carbohydrate levels as other commonly grown beans in Mesoamerica (e.g. black and red varieties of Phaseolus vulgaris). Although tepary bean is low in the amino acids Tryptophan, Methionine, and Cysteine, these amino acids and other complementary nutrients are obtained by eating it in combination with maize and squash. Antinutrients present in tepary bean include trypsin inhibitors that reduce the bioavailability of active trypsin needed for protein digestion, and lectins, which cause red blood cells to agglutinate. Due to the levels of antinutrients in tepary bean, it is considered toxic in its raw state and must be thoroughly cooked before eating. Heat from cooking tepary bean inactivates its antinutrients.
Harvesting of tepary bean presents a challenge as the pod shatters easily at maturity. For small harvests, beans are shelled by hand, although the small seed size makes this process burdensome. Alternatively, threshing involves walking on the pods or beating them with a flail made from a saguaro cactus (Carnegiea gigantea) rib or a mesquite (Prosopis sp.) tree branch. For larger harvests, a threshing floor may be used: The tepary vines are spread over a round depression and a mule or horse is roped to a post in the center and driven around over the vines to crush the pods. The beans are dried before use.
Prior to cooking, tepary beans must be soaked in water for as long as 12 hours. Fresher beans require less time for soaking. Long cooking times, up to three hours, can prove difficult for poor communities where fuel supplies are limited. Cooking times can vary depending on the freshness, production location, seed type, and other factors. Long cooking times are also typical for other beans and precise data comparing cooking times of tepary to other beans are scant, especially for conditions that are typical for rural communities in Mesoamerica.
Because of its high drought tolerance, tepary bean can support diversification of farm systems for climate change adaptation. Tepary bean has been grown historically in Guatemala but it has essentially fallen out of cultivation in current times. The performance of this crop and its acceptability to farmers and consumers in Guatemala are being explored in the Project "Linking agrobiodiversity value chains, climate adaptation and nutrition: Empowering the poor to manage risk" by introducing different varieties through participatory crop evaluation trials. A novel tricot approach developed by Bioversity International is being applied for the trials (see more on ClimMob.net) that are being implemented by Universidad del Valle de Guatemala. Consumer acceptability in urban and rural populations are also being assessed, along with investigations of the value chain. Read more about this work, ongoing from 2015 to 2018 on the IFAD-EU NUS Project page.
