Fava beans

''Vicia faba'', commonly known as the broad bean, fava bean, or faba bean, is a species of vetch, a flowering plant in the pea and bean family Fabaceae. It is widely cultivated as a crop for human consumption, and also as a cover crop. Varieties with smaller, harder seeds that are fed to horses or other animals are called field bean, tic bean or tick bean. Horse bean, ''Vicia faba'' var. ''equina'' Pers., is a variety recognized as an accepted name. This legume is very common in Southern European, Northern European, East Asian, Latin American and North African cuisines.

Some people suffer from favism, a hemolytic response to the consumption of broad beans, a condition linked to a metabolism disorder known as G6PDD. Otherwise the beans, with the outer seed coat removed, can be eaten raw or cooked. In young plants, the outer seed coat can be eaten, and in very young plants, the seed pod can be eaten.

Description

''Vicia faba'' is a stiffly erect, annual plant tall, with two to four stems that are square in cross-section. The leaves are long, pinnate with 2–7 leaflets, and glaucous (grey-green). Unlike most other vetches, the leaves do not have tendrils for climbing over other vegetation.

The flowers are long with five petals; the standard petals are white, the wing petals are white with a black spot (true black, not deep purple or blue as is the case in many "black" colorings) and the keel petals are white. Crimson-flowered broad beans also exist, which were recently saved from extinction. The flowers have a strong sweet scent which is attractive to bees and other pollinators.

The fruit is a broad, leathery pod that is green, but matures to a dark blackish-brown, with a densely downy surface; the wild species has pods that are long and 1 cm diameter, but many modern cultivars developed for food use have pods long and 2–3 cm thick. Each bean pod contains 3–8 seeds. They are round to oval and have a 5–10 mm diameter in the wild plant, but are usually flattened and up to 20–25 mm long, 15 mm broad and 5–10 mm thick in food cultivars. ''V. faba'' has a diploid (2n) chromosome number of 12 (six homologous pairs). Five pairs are acrocentric chromosomes and one pair is metacentric.

History and cultivation

Broad beans have a long tradition of cultivation in Old World agriculture, being among the most ancient plants in cultivation and also among the easiest to grow. However, their wild ancestor has not been identified and their origin is unknown. Charred faba bean remains were discovered at three adjacent Neolithic sites in Israel's Lower Galilee ( Yiftah'el, Ahi'hud and Nahal Zippori). Based on the radiocarbon dating of these remains, scientists now believe that the domestication of the crop may have begun as early as the 11th century BCE.

Broad beans are still often grown as a cover crop to prevent erosion because they can overwinter and, as a legume, they fix nitrogen in the soil. The broad bean has high plant hardiness; it can withstand harsh and cold climates. Unlike most legumes, the broad bean can be grown in soils with high salinity, as well as in clay soil. However, it prefers rich loams.

In much of the English-speaking world, the name "broad bean" is used for the large-seeded cultivars grown for human food, while "horse bean" and "field bean" refer to cultivars with smaller, harder seeds that are more like the wild species and used for animal feed, though their stronger flavour is preferred in some human food recipes, such as falafel. The term "fava bean" (from for the bean) is used in some English-speaking countries such as the US, but "broad bean" is the most common name in Commonwealth countries like the UK, Australia and New Zealand.

Pests and diseases

Many diseases appear at a higher rate in higher humidity. Therefore, cultivars being bred for higher density should be evaluated for disease problems. This can be mitigated by west–east rows for more sun drying effect.

Disease tolerance is an important part of breeding ''V. faba''.

If transplanted instead of direct seeded there is a lower risk of some diseases including ''Botrytis fabae'' (see ''Botrytis fabae'').

Parasites

In mainland Europe and North Africa, the plant parasite '' Orobanche crenata'' (carnation-scented broomrape) can cause severe impacts on fields of broad beans, devastating their yields.

Fungal diseases

''Botrytis fabae''

Beans are attacked by chocolate spot fungus, which can have a severe impact on yield.

'' Botrytis fabae'' is one of the worst diseases in ''V. faba''. Foliar damage, reduced photosynthesis, reduced bean productivity. ''B. fabae'' switches from non-aggressive growth to aggressive pathogenicity under the combination of increased temperature and humidity, and this is worsened by low soil K and P, and by the higher humidity caused by higher seeding rates. The non-aggressive phase is marked by small red-brown leaf lesions, and sometimes the same on stems and pods. Treatment is less effective than prevention. Early planting avoids the problematic combination of high temperature and humidity in late spring into early summer. Decreasing seeding rate or thinning after emergence is also effective. Foliar fungicide is effective. If ''V. faba'' flowers during the heights of summer temperatures there is an increased risk of this disease. If transplanted instead of direct seeded there is a lower risk of ''B. fabae''.

''Erysiphe cichoracearum''

'' Erysiphe cichoracearum'' overwinters on residue and has alternate hosts. Resistant cultivars and overhead irrigation are preventative. Sulfur fungicides are recommended in severe outbreak.

''Fusarium solani''

This soil borne pathogen is mitigated by lower temperature, aeration, drainage, and sufficient nutrition. Symptoms include stunting, yellowing, necrotic basal leaves, and brown or red or black streak-shaped root lesions that growth together and may show above the soil as the disease progresses.

''Uromyces viciae-fabae'' var. ''viciae-fabae''

Faba bean rust is a fungal pathogen commonly affecting broad bean plants at maturity, causing small orange dots with yellow halos on the leaves, which may merge to form an orange lawn on both leaf surfaces.

''Sclerotinia'' stem rot

Both '' Sclerotinia sclerotiorum'' and '' S. trifoliorum'' are pathogens of interest. Lithourgidis et al have done extensive work over the years, including in 2007 for ''S. t.'', 2005 for ''S. s.'', and 1989 regarding procedures for field testing with ''S. s.'' . . .

Bacterial diseases

''Xanthomonas campestris'' and ''X. axonopodis''

''Xanthomonas campestris'' and '' X. axonopodis'' can be inoculated by seed contamination and by overwintering in crop residue. Increased incidence with higher temperatures, rainfall, and humidity. Produces deliquescent, necrotic lesions, sometimes with a wider yellow lesion around them, and in advanced disease the plant will look burned. Can be prevented or treated by use of uninfected seed, resistant cultivars, seed treatments, and copper bactericides.

''Pseudomonas syringae''

''Pseudomonas syringae'' overwinters on residue. Uninfected seed, rotation, and removal of residue are preventative.

Viral diseases

''Faba bean necrotic yellows virus'' which it shares with other ''Vicia''. Timchenko et al 2006 find Clink is not obviously necessary but highly conserved nonetheless, suggesting it is maintained by necessity for infection of other ''Vicia''.

Insect pests

''Aphis fabae''

Broad bean plants are highly susceptible to early summer infestations of the black bean aphid, which can cover large sections of growing plants with infestations, typically starting at the tip of the plant. Severe infestations can significantly reduce yields, and can also cause discolouration of pods and reduction in their saleable values.

'' Aphis fabae'' is a major pest. May infest transplants. Reflective plastic mulch may be preventative. May be mechanically removed by high pressure water once plant is established. ''V. fabae'' is tolerant to low and medium degrees of infestation, so insecticide application is only required under high infestation.

Nutrition

Raw mature fava beans are 11% water, 58% carbohydrates, 26% protein, and 2% fat. A 100-gram reference amount supplies of food energy and numerous essential nutrients in high content (20% or more of the Daily Value, DV). Folate (106% DV), and dietary minerals, such as manganese, phosphorus, magnesium, and iron (range of 52 to 77% DV), have considerable content. B vitamins have moderate to rich content (19 to 48% DV). Fava beans present the highest protein-to-carbohydrate ratio among other popular pulse crops, such as chickpea, pea and lentil. Moreover, their consumption is recommended along with cereals as both foods are complementary in supplying all essential amino acids.

Health concerns

Toxicity

Beans generally contain phytohaemagglutinin, a lectin that occurs naturally in plants, animals, and humans. Most of the relatively low toxin concentrations found in ''V. faba'' can be destroyed by boiling the beans for 10 minutes.

Broad beans are rich in levodopa, and should thus be avoided by those taking irreversible monoamine oxidase inhibitors to prevent a pressor response.

Genetic predisposition

Sufferers of favism must avoid broad beans, as they contain the alkaloid glycoside vicine which may initiate a hemolytic crisis. A low-content vicine-convicine faba bean line was identified in the 1980s and the trait has been introduced into several modern cultivars. Low vicine-convicine faba beans are safe for consumption by G6PD-deficient individuals. As of 2019, a molecular marker may be used for marker-assisted breeding to reduce levels of vicine-convicine in fava beans.

Culinary uses

Broad beans are generally eaten while still young and tender, enabling harvesting to begin as early as the middle of spring for plants started under glass or overwintered in a protected location, but even the main crop sown in early spring will be ready from mid to late summer. Horse beans, left to mature fully, are usually harvested in the late autumn, and are then eaten as a pulse. The immature pods are also cooked and eaten, and the young leaves of the plant can also be eaten, either raw or cooked as a pot herb (like spinach).

Preparing broad beans involves first removing the beans from their pods, then steaming or boiling the beans, either whole or after parboiling them to loosen their exterior coating, which is then removed. The beans can be fried, causing the skin to split open, and then salted and/or spiced to produce a savory, crunchy snack.

Algeria

In south Algerian cuisine, broad beans are used to make besarah and doubara. Doubara is popular in the city of Biskra.

China

In the Sichuan cuisine of China, broad beans are combined with soybeans and chili peppers to produce a spicy fermented bean paste called ''doubanjiang''. Perhaps due to the bean's popularity in Sichuan cuisine, in addition to the regular Chinese terms of "silkworm bean" () or "orchid bean" (), they are also known as "Sichuan beans" () in Chinese.

Colombia

Fava beans (Colombia: Haba(s)) are a common food in most regions of Colombia, mostly in Bogota and Boyacá.

Ecuador

Steamed fava beans (known as ''habitas'') with cheese are common in the cold-weather regions of Ecuador, especially around the Andes mountains and surroundings of Ambato.

Egypt

Fava beans (Egyptian Masri: ' ) are a common staple food in the Egyptian diet, eaten by rich and poor alike. Egyptians eat fava beans in various ways: they may be shelled and then dried, or bought dried and then cooked in water on very low heat for several hours. They are the primary ingredient in Egyptian-style falafel (unlike the Levantine style, where the primary ingredient is chickpeas). The most popular way of preparing them in Egypt is by taking the cooked and partially mashed beans and adding oil, salt, and cumin