Faba beans

Feed value

As ingredients or components for animal and fish feeds, faba beans are well-known sources of protein and energy, although with a low content of certain sulphur amino acids. Faba beans have a total protein content between soybean meal and cereals. As with all raw materials, total crude protein (calculated as nitrogen x 6.25) varies between crops, growing conditions and year; however, on average protein values remain standard, and feed producers use established values for faba beans — about 25%. In a study of commonly grown bean varieties (spring or winter), very few differences were found in protein level between pea varieties (Bastianelli et al., 1995).

1 kg of seeds corresponds to 1.29 feed units and contains 250 g of digestible protein.

Nutritional value of faba beans:

• dry matter — 86%;
• oil — 1.5%;
• starch — 37.0%;
• cellulose — 8.0%;
• minerals — 3.5%;
• protein — 25.0%;
• amino acids:
• lysine — 1.56%;
• methionine — 0.18%;
• cysteine — 0.48%;
• threonine — 0.85%;
• thiamine — 0.21%;
• valine — 1.11%.

For comparison, the feed value of soya (Hy-Pro) is given:

• dry matter — 86%;
• oil — 1.9%;
• cellulose — 6.0%;
• minerals — 6.4%;
• protein — 54.3%;
• amino acids:
• lysine — 2.92%;
• methionine — 0.65%;
• cysteine — 1.35%;
• threonine — 1.86%;
• thiamine — 0.65%;
• valine — 2.27%.

The amino acid composition of beans depends on total protein content and the ratio of different proteins. The lysine level occupies an intermediate position between soybean meal and cereals, which is necessary nutrition for non-ruminants, but beans do not contain sufficient sulphur amino acids or tryptophan.

Starch is the richest component of beans — about 500 g/kg — and represents a valuable energy source for livestock. The average oil content is low (less than 2%). The composition of this oil is similar to that of cereal oils, mainly triglycerides, polyunsaturated in nature with a predominance of linoleic acid.

In faba beans, most varieties contain tannins, but there is insufficient evidence to believe that their content is high enough to affect pig growth (Houdijk et al., 2013).

Many studies have examined the value of beans as a protein source for livestock, and it is recognised that faba beans can be used in nutrient-balanced diets for many ruminant and non-ruminant animals and can fully replace soybean meal without detrimental effects on livestock productivity. In addition, the growing use of faba beans in aquaculture for salmon farming in Norway and Scotland will gradually replace the need for fishmeal in diets.

Varieties

Although there are other representatives of the genus Vicia grown as cultivated plants, for example Vicia sativa (common vetch), Vicia faba is a genetically distant species, and successful interspecific crosses have not been carried out. This limits the variability available for breeding Vicia faba, and cultivar development is made even more difficult by frequent cross-pollination between different varieties, resulting in a wide range of genetic characteristics within a single population.

Depending on seed size, they are divided into:

• small-seeded (v. minor Beok) — 1000-seed weight 200–450 g, seeds cylindrical, plants tall, medium and late ripening from 105 to 140 days, high yield, used for fodder purposes;
• medium-seeded (v. eguina Pers.) — 1000-seed weight 500–700 g, seeds flat-cylindrical, medium and late ripening from 110 to 140 days, plant height from 70 to 200 cm, pods set high, high yield, used for fodder purposes;
• large-seeded (v. major Harz.) — 1000-seed weight 800–2500 g, seeds flat, early ripening from 95 to 105 days, plant height from 50 to 100 cm, pod attachment low, so mechanised harvesting is difficult; cultivated mainly as a vegetable crop for large beans with thick fleshy valves. These beans are also called food, garden, Russian or horse beans.

At the international level, the term “faba bean” is usually used to avoid confusion with other bean species, some of which are also described as field or common beans. The latter belong to the group of bean species (Phaseolus spp.). The term “broad bean” or “broad beans” denotes those varieties of Vicia faba that are harvested before the seeds mature and dry and are used as a vegetable.

The broad bean is also classified into winter and spring types. Winter forms are usually more suitable for cold and heavy soils that are difficult to work in early spring. There are more opportunities for planting winter beans after a dry summer under favourable soil conditions, allowing them to become established as young plants before winter. Varieties tend to have high vigour, allowing rapid germination and emergence under a wide range of conditions. Plants have sufficient opportunity to form several shoots, which help maintain plant height at an acceptable level while compensating for lower plant numbers.

Spring bean varieties are distinguished by a wider diversity of varietal characteristics; some are relatively shorter, mature somewhat earlier and are easier to harvest mechanically. This has allowed the cultivation of spring beans to develop in more northern temperate areas, as well as expanding production opportunities in a number of European and Australian countries. However, the yield of spring beans is negatively affected by water stress and drought, especially during flowering and the reproductive growth phase.

Agriculturally, the development of autumn- and spring-sown field bean varieties has led to significant differences in varieties, cultivation methods, pest and disease characteristics, and the timing and ease of harvesting, so in many respects field beans can be considered different crops. This increases the value of this species for farming systems in many temperate areas and allows selection of the crop type most suitable for specific growing conditions.

Spring and winter forms have different varietal characteristics, including white-flowered and coloured varieties. White-flowered varieties are distinguished by a low tannin content, which is perceived as an anti-nutritional factor in the diet of some livestock species. Coloured varieties are easier to grow, and the production of white-flowered beans is much more difficult because of their capacity for cross-pollination.

Germination

The process of bean seed germination is very similar to that of pea seed germination. In hypogeal germination, the embryonic axis elongates, then ruptures the seed coat, and the apical part of the embryo develops as a plumule that appears above the soil surface, while the seed remains underground.

Vegetative development

The pattern of stem growth depends on the variety and cultivation technology, but the plant's branching habit becomes stronger the earlier the sowing date. Thus, in the winter form sown in autumn, the number of stem branches is higher than in varieties sown in spring. As plant density increases, the number of stem branches per plant decreases. Branching in beans is similar to that of most legumes, since they have a centrifugally arranged series of buds laid down at each leaf axis (Dormer, 1954). Basal branching arises from these buds in the lower part of the stem (Bond and Poulsen, 1983).

Depending on the variety and growing conditions, stem height varies from 120 cm to 200 cm, but environmental conditions such as drought or excess moisture can sharply affect crop height. In general, stem strength is good and allows the plant to remain erect until maturity.

The first two leaves at the base of the stem remain non-living; only small shoots are visible. The first leaflet usually appears at the third node, and the first few leaves have only two leaflets. Leaves usually consist of two pairs of ovate leaflets, although the number of leaflet pairs increases after flower buds are initiated. There are serrated stems, but no tendrils.

Stem growth is influenced by temperature, as well as soil type, moisture availability and incident light. During periods of low light intensity or at high plant density, stem length increases as internodes elongate. Leaf growth is also influenced by environmental conditions, including nutrient availability and water stress.

Root development

Root growth of Vicia faba begins immediately after the seed begins to germinate. Within a week after germination, a well-developed root cap develops, and after 2–3 days the primary root emerges from the seed and lateral root initiation begins. The primary root continues to grow downward, and lateral roots spread from the main taproot. Nodulation occurs when soil-borne bacteria Rhizobium penetrate root hairs, and nodules develop on the upper part of the taproot, where they become abundant. On lateral roots, nodules are generally smaller, but as the plant ages these small nodules take over nitrogen fixation from the older, larger nodules on the main root.

Flower development

Flowering is early, beginning a month after emergence and continuing until the lower pods fill; in a wet summer it continues until autumn frosts.

The petals are joined and mobile, and pollination occurs when an insect presses on the wing and keel of the petal, releasing the stigma and pollen. In this process, pollen is transferred to the hairs of the visiting insect, which can then cross-pollinate other flowers on the same or neighbouring plants.

Flowers emit a strong aroma attractive to pollinators and other insects (Somerville, 2002). Bees play a crucial role in bean pollination. The importance of bees in cross-pollination and improving production is well known (Poulsen, 1975; Svendsen and Brodsgaard, 1997). The most frequent pollinators of Vicia faba flowers in temperate regions are bumblebees (Bombus spp.). In most countries, honey bees (Apis mellifera) collect pollen from Vicia faba, and in some regions hives are often brought to crops during flowering (Bond et al., 1985).

The position of the first flowers and the first pods does not necessarily coincide, since flower drop can occur immediately after petal fall, and the number of flowers per raceme and the number of racemes per plant almost always exceeds the number of pods that develop to maturity. It is believed that about 10% of flowers survive and form mature pods. Environmental conditions have a great influence on this characteristic of field beans, especially under low light intensity or shading in dense plant populations, since the stem elongates and produces more flowers on the upper part of the stem. This can cause the lower flowers (which may even have been fertilised) to drop without forming pods.

Pod development

As the fertilised ovary develops into a pod, the remains of the petals wither and fall, leaving the pod exposed. The number of reproductive nodes with pods varies between varieties, but depends more on environmental conditions. Pods usually form in groups of two or three at each node, starting from the fourth or fifth leaf node and up to the tenth or even higher nodes. Plant density and the number of branches affect the number of pod-bearing nodes, since plants at low population density produce more of them than those growing at high density, provided growth is not limited by water availability, nutrient deficiency or biotic stresses.

Most field bean varieties have dehiscent pods, but the likelihood of their shattering before harvest is lower than in peas. Leaf wilting occurs during seed growth when root activity decreases and increases with rising temperature and water shortage.

Temperature requirements

The heat requirements of faba beans are low; it is considered one of the most cold-resistant vegetable crops.

Seed germination begins at 3–4 °C; the optimal temperature for uniform emergence is 5–6 °C. According to other data, the optimal temperature is +19…+20 °C, at which seedlings appear after 7 days (Autko). Seedlings withstand short-term frosts down to -4…-6 °C.

Average temperatures for growth and development are 15–20 °C. Overwintering forms are able to develop at lower temperatures. The optimal temperature for growth is +18…+19 °C, for flowering and pod setting — +15…+18 °C.

High temperatures above 30 °C suppress growth, primarily during the flowering phase. With extended fruit ripening, autumn frosts pose a danger.

Moisture requirements

Faba beans have increased moisture requirements, especially during the period from emergence to full flowering. Transpiration coefficient 800.

For swelling and germination, seeds need 110–120% water by seed mass.

The broad bean tolerates atmospheric and soil drought poorly. During drought, leaves dry out and fall, leading to a sharp decrease in yield. In dry weather, only the lowest beans set, and the upper buds drop.

Excess moisture is also unfavourable: grain yield decreases because the number of fertilised flowers decreases and damage by diseases and pests increases.

Light requirements

Faba beans are long-day plants.

Soil requirements

They grow well on medium-textured moisture-retentive loamy and well-moistened sandy loam soils with a high organic matter content, as well as on drained peatlands.

pH is an important factor affecting bean yield, and the optimal pH before sowing is about 6.9–7.3 (according to other recommendations 6–7). However, in many arid parts of the world pH values of 8.5 are often found, and this generally does not have a negative effect on yield provided sufficient micronutrients are available. Crops grown on acidic soils are less vigorous, paler in colour and less productive than crops grown at the optimal pH range. Reduced vigour leads to smaller seeds and reduced seed weight per plant. At acidity values below 6, liming is carried out.

It does not tolerate soil salinity. Beans can also be grown on light soils, but they must be moist and well fertilised.

Trials at variety-testing stations showed yields on chernozems 1.2 times higher than on sod-podzolic soils and 1.4 times higher than on grey forest soils.

They have the ability to assimilate sparingly soluble phosphates.

Sandy, stony and waterlogged soils are unsuitable.

Micronutrients

Few micronutrients are important for beans, and those that affect growth or yield are usually corrected by foliar treatment.

Deficiency or unavailability of manganese negatively affects chlorophyll production and can cause chlorosis. It also causes marsh spot, which reduces the quality of seeds or beans for human consumption. This disease most often occurs on highly organic, alkaline or heavily limed soils, as well as when plants are stressed by drought, excess water or compacted soil. Beans are much less sensitive to manganese deficiency than peas, and disease symptoms rarely appear.

Magnesium deficiency is also rare, except on acidic soils. Symptoms are interveinal chlorosis, but leaf edges remain green. Often symptoms of nutrient deficiency can be confused with viruses transmitted by aphids.

Boron deficiency sometimes occurs on some soils and is best corrected with boron-containing fertilisers. Symptoms include interveinal chlorosis beginning at the leaf edges; young leaves may be curled or deformed. Shortened internodes may appear on stems, and all symptoms may occur together.

On alkaline soils in Australia, crops have been shown to respond to zinc; and on acidic soils molybdenum can be applied as a soluble fertiliser.

Seed preparation

Bean seeds (Vicia faba) are generally stronger than those of other legume species, the seed coat is thicker, and the seed size is generally larger. Coloured beans contain tannins in the seed coats, which have antifungal activity, which may be useful for seeds when sown in cool, moist soil, where infection by soilborne Pythium spp. is favoured. Although in some cases there is a relationship between field emergence and seed viability as expressed by the electrical conductivity test, in general seeds appear to perform adequately if initial germination and seed health are satisfactory. However, being a large seed, it is prone to mechanical damage, especially during harvesting, handling and artificial drying, and all these factors can negatively affect seed germination. Damage to seeds by larvae of Bruchus rufimanus, which leave holes in the seeds, can also affect germination or expose damaged seed cotyledons to infection after planting.

An important pest of beans is the stem and bulb nematode Ditylenchus gigas, which is transmitted in seeds, and after emergence neighbouring plants become infected by nematodes. Seed treatment against this pest is recommended.

Seed preparation for sowing consists of sorting and sizing, air-thermal treatment and seed treatment.

Air-thermal treatment is carried out in active ventilation dryers at an air temperature of 30–40 °C for 3–4 hours.

Before sowing, seeds are treated with bacterial preparations and ammonium molybdate at a rate of 0.25–0.50 g of molybdenum per 1 t of seeds. Seed treatment with Rhizotorfin should be carried out on the day of sowing; bacterial preparations are especially effective in fields where beans have not been grown for a long time.

Sowing dates

Sowing methods

There are several methods of planting field beans, including traditional sowing, broadcasting seed on the surface before ploughing, or stubble sowing with zero or minimum tillage. Usually sowing is carried out on previously ploughed soil, but in Western Europe sowing is increasingly carried out using minimum and non-inversion (no-till) soil cultivation. Thus, sowing depth remains more constant, allowing more uniform seed distribution and ensuring emergence, since most seeds are buried to a depth of about 8 cm.

In developing countries or where small areas are grown, broadcasting seed is a common practice, for example in Ethiopia and Lebanon (Lahoud et al., 1979) and to a lesser extent in other countries. In other countries, furrow sowing is carried out, where seeds are placed in separated furrows and then harrowed, or where seeds are individually dropped into small holes made with a small hoe. In most cases, sowing is mechanised using seed drills with adjustable depth and large coulters to prevent seed damage.

Sowing methods for faba beans for seed and green mass are wide-row with row spacing of 45–60 cm (two-row 60x15 cm), and normal row.

Sowing is carried out with grain seed drills with top delivery to reduce seed injury. SPU or SPM-6 series drills can be used for sowing.

In the north, under conditions of sufficient moisture and a short growing season, normal row sowing is used on clean fields. Ripening proceeds somewhat faster and yield is higher. For example, under conditions in Latvia, with the row method of sowing, bean yield was 2.94 t/ha, with wide-row sowing (45 cm) — 2.77 t/ha.

Seeding rates

Winter beans

The pattern of growth differs depending on sowing density, and it is necessary to obtain small autumn bean seedlings at the development stage required for winter protection and a fast-growing spring plant to ensure the creation of a deep root system to withstand possible summer drought. For an autumn-sown crop, determining the optimal plant density is difficult, since the formation of plants surviving to the next spring may be more variable than in spring-sown crops. In addition, disease pressure from fungal pathogens such as chocolate spot (Botrytis fabae) can alter the yield response to plant density.

Economic response of winter beans to increasing plant density (Armitage, 2009).

Recent work in the United Kingdom has shown the effect of early sowing and dense planting on chocolate spot incidence. With a reduced plant population, chocolate spot has a much smaller effect on growth in early spring. Similarly, sowing time affects bean seeding rate, especially with autumn sowing. Beans planted in early autumn are more susceptible to chocolate spot at higher density (Maguire, 2013). With autumn sowing of beans, low planting density allows increased weed competition, increased branching in earlier-sown crops, and pods form lower on the stem, which increases yield losses due to poor pod collection during harvest. At high crop density, the risk of disease increases, the risk of lodging increases on soils with increased moisture capacity, and yield may decrease due to poor pollination and seed setting (Armitage, 2009).

The success of crops is usually judged by their establishment and the number of plants surviving in spring. Many old winter bean varieties were indeterminate and prone to lodging at densities above 18 plants/m². With the introduction of more compact varieties, evidence has appeared that higher population density is economically more advantageous, and in the United Kingdom densities up to 25 plants/m² are common. As with all optimal density curves, increasing plant density increases seed cost, so the optimal economic seeding rate takes seed cost into account. The figure below illustrates the relationship between increasing seeding rate and yield and shows the yield response and economic response curves. The results are taken from recent work in the United Kingdom with the winter bean variety Wizard (Armitage, 2009).

Sowing depth

Large bean seeds are sown on heavy soils to a depth of 4–6 cm, and on light soils — 7–8 cm.

Winter beans can be planted somewhat deeper than spring crops to avoid damage by rodents or birds.

Cultural control methods

When growing beans, stubble cleaning and seed burial methods are usually used, although they do not reduce populations of weeds growing from depth, such as residual seeds of oilseed rape and charlock (Sinapis arvensis).

Mechanical soil cultivation in crops has the disadvantage that it does not control weeds in the row and may require more than one operation. On winter beans, harrows are often used, and if growing points are damaged, plants compensate by producing new branches from the base. However, beans must be grown in wide rows (40 cm) to facilitate passage between them.

The frequency of soil cultivation required for adequate weed control depends on the sowing date, the number of weed species and growing conditions. For spring beans, early weed removal by cultivation 4–6 weeks after emergence is important. For winter beans, more frequent cultivation may be required, since weeds take longer to germinate. Finger weeding with an Einbock-type finger weeder can also be used, especially on spring beans, until they have grown too tall.

Biofumigants

Biofumigants have been used for many years, and significant research is currently ongoing into the use of these methods on annual crops. The technique is based on incorporating fresh, mulched plant material into the soil, which releases several substances capable of suppressing soilborne pests or diseases, and in some cases it is claimed that weeds are also suppressed. Plants of the genus Cabbage (Brassica spp.) are particularly active accumulators of sulphur and synthesise significant amounts of sulphur-rich glucosinolates. Damaged leaves release myrosinase enzymes, which break down glucosinolates into several products, including isothiocyanates (very toxic). Work has shown that these products are active against some soilborne diseases and pests, but there are claims that weed suppression can also be achieved.

Growing a Brassica cover crop for use as a biofumigant involves establishing an autumn-sown crop, usually mustard, in particular mustard (brown mustard, Brassica juncea), although other representatives of the celery family (Apiaceae) can also be used.

While the use of such cover crops has a number of advantages in agriculture, such as providing a source of nutrients for newly developing crops, helping to improve soil structure by adding organic matter, and having a certain effect on suppressing pests such as nematodes, there is little reliable information that this technique can become a sustainable means of weed suppression in pea and bean crops. It has been suggested that crucifers may have an allelopathic effect on weeds, and reports from Europe and North America also state that crucifers can be used for integrated weed management (Tollsten and Bergstrom, 1988; Turk et al., 2005). However, there are no reliable data indicating a reduction in weed numbers in a growing crop (Haramoto and Gallandt, 2005a,b). Similarly, there are reports of suppression of black-grass (Alopecurus myosuroides) with a mustard cover crop preceding spring sowing of faba beans (Jim Scrimshaw), but the effect was not repeated on beans from year to year, although other work on winter cereals has shown significant suppression. This may be partly due to insufficient persistence of glucosinolates in the soil during the weed germination period, or other factors may be involved.

Herbicides

In the United Kingdom and other European countries, pre-emergence residual herbicides must be used, since there is only one post-emergence herbicide.

There are no herbicides for controlling thistles and docks (Rumex sp.), since translocated substances such as clopyralid or MCPB and MCPA damage beans. Most pre-emergence preparations require a minimum incorporation depth, and dosage may depend on soil type.

Where a problem with cleavers (Galium aparine) is expected, clomazone in a tank mixture is effective. Imazamox and pendimethalin or prosulfocarb can be applied pre-emergence on both spring and winter beans, but linuron can be used only on the spring crop. On winter beans, limited broad-leaved weed control is provided by propyzamide or carbetamide, but these are used mainly for grass-weed control. Bentazone is the only post-emergence preparation for broad-leaved weed control. Tri-allate is often used to control wild oat, as well as quizalofop or tepraloxydim (PGRO, 2016).

Among pre-emergence herbicides, soil spraying with prometryn at a rate of 3–4 kg/ha of preparation can be used.

For beans (Vicia sp.) and beans (Phaseolus sp.), bentazone is the only material safe for use as a post-emergence herbicide for controlling broad-leaved (dicotyledonous) weeds. The selective action of bentazone may be related to differential retention and uptake, as well as the ability to metabolise bentazone.

Faba beans

To accelerate ripening, a month before harvest, topping (pinching) is carried out, that is, removal of 10–12 cm of the top of the main stems. This technique also reduces plant damage by aphids.

Acceleration of bean ripening is also affected by leaf removal. For this, plants are sprayed with preparations that cause drying and falling of leaves, for example, 10–15% solutions of ammonium nitrate or sulphate. Crops are treated 2–3 weeks before harvest.

In some seasons, pod ripening is uneven, and the upper pods remain green longer. Bean pods blacken, and seeds become dry and hard earlier than the stems of most plants. Pods thresh easily when moisture content is 16–20%, but usually it is necessary to wait until most stems become brown and dry. Overdrying can lead to shattering and large losses during combining.

At full maturity, beans tend to crack and seeds shatter, especially in dry years. Therefore, the preferred harvesting method is two-phase; harvesting begins when 25% of the lower pods turn brown. In dry and warm weather, seeds ripen well and retain high sowing qualities.

Tall, non-lodging varieties can be harvested in one phase or two phases. In the two-phase method, it is desirable to place the cut mass on high stubble. Drying of windrows lasts 5–10 days; overdrying leads to losses from pod cracking and seed shattering. Threshing of windrows is carried out at a drum speed of 400–500 revolutions per minute.

When 85–90% of pods blacken, harvesting is carried out in one phase. In this case, defoliation is carried out 2–3 weeks before.

Because of the large seed size, the rotational speed of the harvester drum should be minimal, and the concave clearance should be maximum.

After harvesting, beans can be dried using ambient or slightly heated air until the optimal storage state of 85% dry matter of beans is reached.

Dry bean haulm can be used as livestock feed, and after harvesting it can be pressed into bales for storage.

After harvesting, beans can be stored satisfactorily at 14% moisture. If drying is required, the method used depends on the market. Field beans grown for seed or premium niche markets require drying and storage so that germination and quality are not affected by damage such as seed coat cracking or seed splitting. For the animal feed market, the only criteria are maximum moisture content, impurity level and absence of mould, so beans do not require such gentle drying. Flour may become pasty if insufficient moisture is removed from the centre of the beans, and it may become rancid during prolonged storage.

Cleaning beans before use is usually carried out by specialised traders, and the procedures are similar to those used for cleaning peas. Spotted, broken and foreign impurities are removed. If beans are intended for human consumption, they are cleaned in a drum cleaner to remove beans that have been damaged by the bean seed beetle (Bruchus rufimanus).

Vegetable beans

Bean maturity is assessed in the same way as peas, using a tenderometer. However, the tenderometer is not an absolute indicator of quality, since its readings are the average value of all beans in a sample, which may contain beans of different degrees of maturity. Also, using organoleptic tests, it has been established that the optimal quality for a particular variety may be observed at different ripening times when grown under different conditions; similarly, optimal quality may be observed at different ripening times in different varieties. Under dry conditions, the skin may become tough more quickly, as chemical processes occur in the beans. In the absence of more critical methods, a combination of tenderometer readings and organoleptic tests is often used.

Beans are usually harvested directly in the field using green pea harvesters (viners) equipped with modified pickup drums to work with a taller crop, or they are first cut and left in windrows for 24 hours to allow the crop to wilt slightly, which in some situations can help with threshing.

Beans are unloaded from mobile viners into tanks for transport either directly to the plant or to a cleaning and cooling line on the farm. They are then transported in sealed containers to reduce discolouration of green beans. Before blanching and freezing, beans are cleaned again at the plant.

If immature seeds are to be used for food, beans can be harvested when the seeds reach full size for the variety but are still at the milk stage. The yield of beans at the technical ripeness stage is 10 t/ha, and of grain — 4 t/ha. Beans are harvested as they ripen in 3–4 passes with an interval between harvests of 8–12 days. They are picked with a sharp downward movement, trying not to damage the plant.

Beans can be canned in the same way as peas. In extreme cases, when there is no suitable crop near the plant, canning can be carried out using frozen beans. As with frozen peas, beans are produced under contract with processing companies, and sales are usually made by the processor to retailers.

Podded (broad) vegetable beans for manual harvesting are usually grown in wider rows to provide access for pickers. Maturity assessment is sometimes carried out on a tenderometer, but often the criteria for harvesting are based on visual inspection of the pods, their length and degree of filling, and samples are taken to determine seed size and seed-to-pod ratio by weight. For the fresh market, a certain pod width and length, a minimum number of beans per pod, and a seed-to-pod ratio of about 35% are required. Pods are harvested manually and delivered to the packing plant in boxes before prepacking and transport to retail.

Podded vegetable beans can be fully harvested during the milk stage, when the valves are succulent and the grains reach a size of 1 cm. At this time, the beans break easily and reach a length of 5–7 cm; the outlines of the seeds begin to show through the bean skin, and the seed hilum has not lost its white or green colour.

Desiccants

Desiccation for faba (dry) beans is usually rarely used.

Preparation Reglone Super, spraying crops when the lower pods turn yellow and the seed hilum blackens.

Bean downy mildew (Peronospora viciae)

Bean downy mildew (Peronospora viciae, English Bean downy mildew) also affects peas, but it has not been proven that isolates of bean downy mildew can be successfully inoculated onto peas, and it is believed that among populations of Peronospora viciae there are separate pathotypes that may be specific to Vicia faba. The disease has been recorded in many temperate regions of the world, but mainly where early growing conditions are cool and humid.

The symptoms of the disease resemble those that occur when peas are infected by pea downy mildew. Initial infection begins with soil inoculum consisting of oospores, which infect germinating bean seedlings. As a result, infection develops systemically in seedlings, forming stunted pale plants on which oospores are formed from mycelium on the underside of leaves. Infection spreads as secondary infection to surrounding plants, often ending in complete distortion of the growing tip, covered with a characteristic grey-lilac mycelium. The pathogen has not been established to be transmitted through seeds.

Conditions favourable for infection were determined from a combination of temperature and air humidity (Biddle et al., 2003), which led to the development of a forecasting system. The system, which is used by growers in the United Kingdom to determine infection risk and decision support systems for spraying, was available online for UK growers (CropMonitor).

Bean downy mildew can be controlled with phenylamide fungicides, and seed treatment may also be effective. There are several varieties of Vicia faba that have a higher level of field resistance to the disease than others, and this characteristic is included in the recommended list of bean varieties in the United Kingdom (PGRO, 2015).

Chocolate spot (Botrytis fabae)

Chocolate spot (English Chocolate spot).

Pathogen: Botrytis fabae, as well as Botrytis cinerea.

The disease develops in summer with prolonged wet and cloudy periods. It occurs in all regions of the world where field beans are grown, but causes serious losses only under favourable conditions. Yield loss due to defoliation and reduction of photosynthetic area is the main problem, and beans for the fresh market, harvested as whole pods, can be spoiled by spotting and rot that appear on infected plants.

Symptoms of chocolate spot differ from other leaf and pod spot diseases in that there is no clear formation of fungal fruiting bodies, as in the case of Ascochyta fabae.

Autumn sowings are more susceptible to infection, since it can begin in autumn and remain at a low level until spring, when weather conditions favourable for development occur. High planting density promotes disease development, and planting date also affects the amount and aggressiveness of developing disease.

The use of fungicides to control chocolate spot is a routine procedure in most temperate countries, and dependence on fungicides is complete, since there are no significant differences in variety resistance to this disease. Application timing is key for effective control (Gladders et al., 1991).

Chocolate spot (Botrytis fabae) on beans.

Chocolate spot (Botrytis fabae) on beans.

Leaf and pod spot (Ascochyta fabae)

Leaf and pod spot, or brown spot (English Leaf and pod spot).

Pathogen: fungus Ascochyta fabae (syn. Ascochyta vicia fabae (Speg.)), a related pathogen causing leaf and pod spot of peas, is specific to beans and is the only pathogen seriously affecting their yield and quality. Infection can lead to plant death.

On beans, the disease manifests as deep round or elongated brown spots with a dark red border and fruiting bodies. Damaged leaves dry out prematurely, stems become distorted, plants are stunted, pods rot and produce shrivelled seeds. Infected seeds with brown spots lose germination capacity.

It is transmitted mainly by seeds and develops on seedlings soon after emergence. Pycnidia formed in disease foci on stems, leaves or pods contain spores that are released and splashed by rain or water droplets. Internal infection can occur, leading to deep seed infection. Spores can also be transmitted by wind from pycnidia formed on overwintered infected crop residues, where the sexual form of Ascochyta fabae (syn. Didymella fabae) develops in autumn and winter (Jellis and Punithalingam, 1991).

Chemical control has been mainly unsuccessful, and the health of Vicia faba beans in the United Kingdom was maintained by strict certification procedures until the mid-1990s. Since then, breeders and seed growers have maintained voluntary standards. Resistance to Ascochyta fabae was identified in winter beans in the United Kingdom several years ago (Bond and Pope, 1980), and since then efforts have been made in Europe and other countries to breed fully resistant varieties.

Brown rust (Uromyces fabae)

Brown rust (Uromyces fabae) on beans.

Brown rust (English Brown rust) is widespread in most regions of the world where beans are grown and has become one of the main causes of yield loss in both field (faba) and broad (vegetable) beans. Beans, both spring and winter varieties, can be affected at any stage of the growing season.

Pathogen: fungus Uromyces fabae.

Leaves become infected from flowering onwards, but the most serious infections may begin at the end of the season, after a period of warm days and cool nights with high humidity. Due to the influence of weather conditions, later-maturing beans planted in spring are often more susceptible to infection, although in some seasons autumn sowings may also be affected. Rust spores can survive as telia in a semi-dormant state during winter on crop residues or on volunteer beans.

Rust causes partial defoliation and loss of photosynthetic area, leading to significant yield losses, especially if infection begins at the pod development stage. Pustules may form on stems and pods, and severe infection causes poor seed development. In the case of vegetable beans, spoiled pods may become unsaleable.

Although rust control with systemic fungicides is effective, there are some differences in susceptibility between varieties, especially in Europe, where some spring bean varieties are more resistant than others. Incomplete resistance is usually found, but hypersensitive resistance has been identified quite recently (Rojas-Molina et al., 2010), although varieties with complete resistance have not yet been bred (Adhikari et al., 2012).

Viral diseases

Beans (Vicia faba) can be infected by several viruses, some of which are seed-borne, but most of the 18 or so viruses described worldwide are transmitted by aphids or other insects (Kumari and van Leur, 2011). In Europe, viruses such as bean leaf roll virus (BLRV), which is transmitted by the pea aphid and black bean aphid, and pea enation mosaic virus (PEMV), which is also transmitted by the pea aphid, are common. Often both diseases occur together, and infected crops show various symptoms, including classic leaf rolling, wrinkling of upper leaves, development of translucent spotting on leaves, deformed and stunted pods and internodes, which are often confused with symptoms of manganese deficiency.

In Africa and the Middle East, one of the most common viruses is faba bean necrotic yellows virus (FBNYV), which is effectively transmitted by Aphis craccivora from a number of wild host plants. In Australia, beet western yellows virus is common in some areas, and pea mosaic virus, transmitted by aphids from nearby infected pea crops, can also lead to quality loss due to seed coat defects.

There are no reports of variety resistance to any of the common viruses, so attention for control and management is directed towards crop hygiene, weed control and pesticide application.

Stem nematode (Ditylenchus gigas)

Stem nematode (Ditylenchus gigas, English Stem nematode), officially known as the “giant” race of Ditylenchus dipsaci, is a free-living nematode that can survive in soil for several years. It has been found on Vicia beans in many regions of the world, especially where Vicia faba has been grown for many years. This species is specific to Vicia beans, and although other nematode species (Ditylenchus gigas) can affect beans, they are not the cause of serious yield losses.

Damage is often observed when plants reach flowering, but in young seedlings severe symptoms may appear even earlier, especially under wet conditions. Plants are stunted, stems thicken and twist. Blisters often appear on the stem, which may become reddish. The infected stem may collapse. Leaves are deformed on the petiole, and growing points may be affected in a similar way. Pods do not develop, and if seeds appear, they are black and shrivelled, or the seed coats may be discoloured in small patches. Affected plants occur singly or in large patches in the field, and both winter and spring beans can be affected.

The effect on yield is strongly manifested at high pest numbers. In beans intended for human consumption, seeds may be discoloured, and their presence may lead to rejection by processors.

Stem nematodes are transmitted both by seeds and soil. After infection, nematodes move inside the plant and multiply in tissues, after which some of them move into the developing seed and the mass under the seed coat. They then withstand drying and survive inside the seed for 2 years. Infected seeds can be transported, and when planted the nematodes re-infect the developing plant, and populations move to surrounding plants, thereby causing new infection in clean fields.

Since the pest can be transmitted by seeds, the only means of controlling it is to produce seeds in uninfected fields and strictly test seeds. The testing method is based on extracting nematodes from seeds by soaking in water for 24 hours and microscopic examination of the soaking water (Augustin and Sikora, 1989), and this method is used by many seed testing laboratories. Several European researchers are currently evaluating molecular testing procedures. If nematodes are found in a sample, the seeds must not be used for sowing (PGRO, 2015). Attempts have been made to screen lines of Vicia faba from the ICARDA germplasm collection for resistance to Ditylenchus gigas, and breeding work is at an advanced stage in developing a field bean variety with some resistance to the nematode (Stawniak, 2011).

Black bean aphid (Aphis fabae)

Black bean aphid (Aphis fabae).

Black bean aphid (Aphis fabae, English Black bean aphid) is the main pest of faba beans and sometimes peas, but can occur in large numbers on beans, spinach and sugar beet, where populations colonising the underside of leaves can become chlorotic and wrinkled.

Aphis fabae occurs in many countries, including Scandinavia, Europe, Asia, the Middle East, part of Africa, North and South America, but is not widespread in the tropics. The related black aphid Aphis craccivora is widespread in warmer countries, where a temperature of about 24 °C is more favourable for its development. This species has a wide host range and includes most grain legumes and plants.

Colonies of Aphis fabae increase rapidly on bean plants, especially on the growing shoot, where they cause direct feeding damage, reducing the number of flowering pods and apical growth. In addition to feeding, they are vectors of viruses, including bean leaf roll virus (BLRV) and bean yellow mosaic virus (BYMV). Together with the pea aphid, they can also transmit pea enation mosaic virus (PEMV), which in combination with BLRV can cause a significant reduction in yield. Yield reduction depends on the degree of infestation, but yield losses are high where colonies are dense around flowering and podding nodes.

The effect of viral infection on yield and quality can also vary from insignificant to severe, with distortion and poor seed development or discolouration of the seed coat, leading to rejection of the crop.

Aphids migrate to bean crops in late spring or early summer and colonise the tops of plants before developing large dense colonies of many hundreds of individuals.

After colonisation, winged aphids leave the crops and lay eggs on overwintering hosts, for example European spindle (Euonymus europaeus). Aphis craccivora has a similar life cycle to Aphis fabae, but its woody overwintering hosts are laburnum (Laburnum anagyroides) and broom (Cytisus scoparius).

Control of both species is based on insecticide treatment at the first detection of colonies and before flowering, since early-migrating aphids can begin transmitting virus immediately after feeding begins.

Bean seed beetle (Bruchus rufimanus)

Bean seed beetle (Bruchus rufimanus).

Bean seed beetle (Bruchus rufimanus, English Bean seed beetle) is the most damaging pest of faba beans Vicia faba and is present in many temperate countries.

The main impact on beans is infestation of developing seeds by larvae and pupae of this insect. Fresh beans can be spoiled by larval entry holes, which become visible after the pods are opened. Beans will also contain larvae at this early stage, and produce for processing or the fresh market will be unsaleable. In the dried crop, the presence of pupae or unemerged adults creates problems for exporting beans for human consumption, and beans with exit holes are also unsuitable for high-quality markets unless they are removed mechanically during cleaning.

Unlike closely related bruchid beetles, Bruchus rufimanus has only one generation per year and relies on its development on the growing crop. It is not a pest of stored products. Adults fly to beans at the beginning of flowering and feed on pollen for 2 weeks before becoming sexually mature. At this point, females lay eggs on developing pods; after a few days, larvae hatch from the eggs and burrow into the pod and developing seed. The larvae feed on the cotyledon until the seed and larva reach maturity. At this stage, the larvae pupate and emerge as adults shortly before or immediately after harvest, leaving round exit holes in the beans. The adults then fly to overwintering sites, which include wooded hedgerows and tree bark in scrub around the field.

Attempts have been made to create a monitoring system for the presence of bruchids in crops, and limited success has been achieved using cone traps baited with floral volatiles, which proved effective in catching adults when they move to crops, but not attractive enough to compete with crops after flowering begins (Ward and Smart, 2011). In France, decision support systems operate for bean growers to determine spraying time, and a similar system (Bruchidcast) has recently been developed in the United Kingdom on the Internet. Both systems use daily temperature to determine the period of bruchid activity so that insecticides can be applied during egg laying.

Limited screening for resistance to Bruchus rufimanus has been carried out in Vicia beans, but resistant varieties have not yet been bred.

History of modern cultivar development

Until recently, there was practically no scientific approach to field bean breeding. This may be explained by the fact that it is a cross-pollinated species, where pure-line breeding approaches are not relevant, and there are no easily developed Mendelian markers for traits. Therefore, the varieties grown and sold were not often precisely defined or clearly distinguishable from each other. It is believed that Vicia faba could have originated from two or three ancestors of the genus Vicia, Vicia narbonensis (Narbonne vetch), Vicia galilaea and Vicia hyaeniscamus, but there is very little evidence of its relationship with these three species (Ladizinski, 1975). It has also not been possible to cross Vicia faba with any of these species, and this currently limits the variability available for breeding Vicia faba varieties, especially since Vicia narbonensis has good resistance to some common bean diseases.

In its domesticated form, Vicia faba remains a separate species, although some of the small-seeded forms are known as Vicia faba subsp. minor, and the larger ones as subsp. major or equina. However, there is no evidence that there are any barriers to gene flow between seed size classes, so botanically they should not be classified as subspecies, since arbitrarily defined seed size ranges are more or less simply market classes. The sources of variation that do exist in Vicia faba are found in the broad gene pool of its domesticated form, to some extent facilitated by the popularity of beans, especially large-seeded ones, as a garden vegetable and as a field crop harvested dry. There are some mutational changes caused by chemical or radiation treatment (Sjodin, 1971), but in general modern Vicia faba varieties have been created using conventional breeding methods.

The recent development of doubled haploids using anther and pollen culture has proven applicable to Vicia faba, and at least one variety is currently sold on the market.

Despite some autofertility of plant flowers, Vicia faba is partially allogamous and can cross-pollinate through insects, mainly bumblebees (Bombus spp.). This has several important consequences for bean breeding that should be noted. The development and maintenance of pure lines requires complete exclusion of pollinators, which is a large overhead for a breeding programme and makes the release of pure inbred varieties more or less impossible. The use of male sterility to ensure maximum hybrid vigour has been preliminarily studied, but a commercially viable hybrid production system has never been created. A compromise solution is to use the natural tendency for one third to two thirds of seeds to be formed as a result of outcrossing by creating so-called “synthetic” varieties, in which several founder individuals having some common characteristics but by no means homologous are allowed to cross freely, giving a certain degree of hybridity that may decline over several generations of multiplication in the absence of optimal pollinator populations (Obiadalla-Ali et al., 2015).

Beans are able to adapt to environmental conditions, and because they were more widely grown in areas north and south of the Mediterranean, varieties arose based on the use of their adaptations rather than specific breeding methods. Adaptations include winter hardiness, reduced pod shattering (dehiscence), seed size and changes in seed colour. Recently bred bean varieties include varieties with winter hardiness, allowing them to be sown in autumn, spring-sown varieties with more determinate stem growth to reduce lodging, medium seed size and light brown or green seed coats. The green seed character, as a result of persistent chlorophyll, has been identified as a single recessive gene-determined trait and has been used for vegetable beans in China and other countries.

Despite its popularity since domestication, the area sown to beans has declined very strongly over the past century as a result of the introduction of mechanical labour, since field beans were a main ingredient for feeding oxen, horses and mules. Also, very little effort was put into plant breeding to develop new varieties that would be better adapted to modern agriculture. This meant that beans had low yield and poor yield stability, especially during periods of drought or excessive moisture, indeterminate growth leading to excessive stem growth and susceptibility to lodging, relatively low disease resistance and the presence of anti-nutritional factors, which reduced their suitability as feed for many livestock species. However, as interest in this crop began to increase due to the desire to produce more sustainable sources of plant protein and the value of grain legumes in arable rotations and in less developed agricultural systems, significant progress has recently been made in both breeding and agronomy.

Modern varieties have a more determinate habit (that is, cessation of vegetative growth when flowering and pod setting begin), low anti-nutritional factors and increased resistance to the most common diseases, including ascochyta blight (Ascochyta fabae), rust (Uromyces viciae-fabae) and downy mildew (Peronospora viciae), as well as resistance to crenate broomrape (Orobanche crenata). Advances in genomics allow the creation of a gene map; marker-assisted selection is being carried out, as well as work on synteny with other legumes such as peas and barrel medic (Medicago truncatula).

The full genetic potential of Vicia faba is still being studied, including leaf architecture, pod wall characteristics, stem determinacy, factors affecting flower setting and pod set, and aspects of seed quality such as protein content and reduction of anti-nutritional factors, including tannins (Stoddart, 1986).

Because of the indeterminate habit, stems may produce excessive growth at the expense of reproductive nodes. Competition for light and pollinators leads to poor flower retention and formation of smaller pods at the top of stems, making the crop slow to mature and difficult to harvest. Breeders were offered a variety with a terminal inflorescence (ti type). This variety had a stiff stem with an inflorescence at the top of the stem. However, this was somewhat extreme, and the type was less able to adapt to variable climatic conditions during growth and did not become widespread. Work is currently underway to identify markers for determinate types (Alvila et al., 2007).

The most important fungal leaf diseases are chocolate spot (Botrytis fabae), Ascochyta fabae and Uromyces viciae-fabae. In some areas, soilborne root fungi Rhizoctonia solani and Fusarium spp. occur, especially on soils with a long history of field bean cultivation. Botrytis occurs over a wide range of growing conditions; it often poses a very serious threat, but information on the source of resistance is very limited, although several less susceptible bean genotypes are known (for example, ICARDA lines originating from Ecuador). For Ascochyta and Uromyces, specific resistances are known and molecular markers have been developed. Downy mildew causes other, less well-studied leaf diseases of Vicia faba, but, as with peas, there are several pathogen races, and complete resistance to downy mildew is unknown. Breeders rely on selecting less susceptible varieties for commercialisation. Viruses can be a frequent problem, and viral diseases can appear as an epidemic and become serious. Pea enation mosaic, bean yellow mosaic virus, bean leaf roll virus, bean common mosaic virus and bean spot virus are common. The impact of aphid-borne viruses can be reduced by effective plant protection methods, but seed-borne viruses can pose a greater problem. The most important pests are Aphis fabae (black aphid) and Acyrthosiphon pisum (pea aphid). In addition to direct feeding damage, virus transmission occurs when aphids introduce infection early in the growing season, and useful resistance to them is unknown.

Faba beans can be infected by the stem nematode Ditylenchus gigas, which is widespread and common, especially where nematode-infected seeds are used. Recent work has identified potential breeding material showing resistance to the nematode, and developments are currently underway to evaluate the potential of this material to provide a reliable level of resistance. Crenate broomrape (Orobanche crenata) is a parasitic plant damaging legumes and other crops in the Mediterranean basin and the Nile valley. Partially resistant genotypes are available; the trait shows quantitative genetic variation, and three quantitative trait loci (QTL) for resistance have recently been identified (Torres et al., 2006). Several sources of resistance to root rot are known. Varieties with low tannin content in the seed coat have been bred, but since these varieties are usually white-flowered, difficulties in propagating homozygous stocks make commercial introduction very expensive.

The degree of cross-pollination by bees and other flying insects is about 50%, with a large genotypic and environmental component of variation and pronounced heterosis, where heterozygous types show on average less outcrossing; and under open-field conditions seed production suffers from cross-pollination contamination unless spatial isolation and pure lines are used.

Despite limitations in breeding ideal beans, breeders have made significant progress in developing a steady stream of new varieties for commercial production. In Europe, significant advances have been made in increasing yield, and the recently bred varieties Fanfare and Vertigo have clearly demonstrated this improvement and are currently grown on a significant scale.

Fodder Bean Varieties

Fodder beans grown for dry harvest (field beans) are usually either winter types, when they are sown in autumn and are more frost-resistant, or spring types, which are usually sown as early as possible in spring to achieve their full yield potential.

The seeds are mainly used as a source of plant protein for animal and aquaculture feed, although dried horse beans also form an important part of the human diet in Africa and the Middle East. Seed quality for the human consumption market is important in that the beans should be plump rather than flat, with an even light-brown skin color and a pale-colored (so-called white) hilum. Because European and Australian producers are interested in supplying these markets, most faba bean varieties have been selected for these characteristics.

For animal feed there are no special requirements for color or shape; beans may also have a black core, although the presence of heavily decomposed broken seeds or a high level of insect damage can reduce the value of the crop. It was believed that the presence of antinutritional factors such as tannins negatively affects the high inclusion rate of beans in compound feeds; however, recent studies have shown that the presence of tannins from beans in pig diets does not lead to negative growth or digestibility indicators in fattening pigs.

In the UK there is a small market for racing pigeon feed, which requires small round seeds. Currently, one variety, Maris Bead, is grown for these purposes; it has been used commercially since 1964. Because of the very small market for these beans (known as tick beans), no breeding work has been carried out in recent years.

Recently, faba bean varieties with improved nutritional properties have been developed, including tannin-free varieties (e.g. Gloria), as well as varieties with low vicine and convicine content. These two glycosides are associated with poor digestion rate in animals and a disorder known as favism in humans, when a person has a deficiency of glucose-6-phosphate dehydrogenase activity.

These low-vicine varieties were registered in France by INRA (National Institute for Agricultural Research) and are known as Fevita varieties. Some of them may be preferable for specialized animal feed producers, although in the UK and Canada there appear to be no commercial advantages of these types as yet.

Varieties of both spring and winter beans undergo field variety trials in the UK, as well as in a number of European countries, Australia, and Canada. Existing varieties are listed in the UK in the Recommended List and are updated annually.

Vegetable Bean Varieties

Within Vicia faba there are two main types of beans based on their use, described here: beans harvested at the immature green stage, when the seeds are extracted from the pod and consumed as a vegetable; and a type harvested when fully ripe to obtain dry seeds used for a range of purposes in human or animal food. Vegetable beans, known as broad beans, are grown either for the fresh market or for large-scale commercial freezing or canning. Varieties have been bred with regard to the appearance, taste, texture, and color of immature seeds, which can vary from pale green to dark green, from very large in size or slightly flattened in shape to small and almost round beans. Crop height also varies among varieties. Very short dwarf varieties, such as Sutton, have very few vegetative nodes and begin their reproductive stage at nodes that are still very low to the ground. Often these varieties are earlier-maturing than tall varieties. Pods are formed in dense clusters around the stem. Some varieties are more frost-resistant and can be sown in autumn to obtain an early harvest. Seed set can be a problem for varieties sown in autumn, since insect activity during flowering may be low in the cool period, which can lead to uneven seed set in pods. The Aquadulce variety is often sown in autumn for the fresh market.

Two main types of beans are grown: those with white flowers, which are suitable for canning; and those with colored flowers, which are suitable for freezing, although most varieties grown for freezing have white flowers.

Beans for the fresh market can have either white or colored flowers. Colored flowers indicate the presence of leuco-anthocyanins, which break down on cooking into colored polyphenols, giving pink or brown beans in cloudy brine when canned. The freezing market requires beans with uniform seed size and color, while the fresh produce market requires pod width and length within certain size ranges, a minimum number of beans per pod, and a seed-to-pod ratio of about 35%.