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Fagopyrum esculentum Moench

Protologue
Methodus: 290 (1794).
Family
Polygonaceae
Chromosome number
2n = 16, 32
Vernacular names
Buckwheat, beech wheat (En). Sarrasin, blé noir (Fr). Trigo sarraceno, fagópiro, trigo-mourisco (Po).
Origin and geographic distribution
Buckwheat is native to central and northern Asia and was domesticated in south-western China (Yunnan, Sichuan provinces) from wild types. For over a thousand years buckwheat has been an important subsistence and cash crop from northern India and southern China to Korea and Japan. In the early Middle Ages it was introduced into Europe and became a leading crop on poor soils and an important staple food. European emigrants introduced buckwheat in the United States and Canada. The increased use of chemical fertilizer in the beginning of the 20th century led to an enormous decrease of the buckwheat area in Europe and North America and replacement by higher yielding crops such as rye, oats, maize, wheat, and Irish potato. Buckwheat is still important in India, China, Korea, Japan and eastern Europe. In tropical Africa (e.g. DR Congo, Ethiopia, Uganda, Zimbabwe, Réunion) and South Africa it is cultivated sporadically and it also occurs as an introduced weed.
Uses
The seed of buckwheat is cooked like rice or made into flour for the preparation of noodles, pancakes, porridge, cakes and biscuits. It is an ingredient in breakfast cereals. Groats is the part of the seed left after hulling. Buckwheat seed is often ground or milled coarsely, to produce broken groats. Many consumers like the coarsely milled flour which is brownish because of the high content of hull particles. At present, high fibre content is considered a favourable character, and buckwheat is gaining importance as a health food. Buckwheat has a particular taste, liked by some, rejected by others. When sieved for almost white buckwheat flour, the extraction rate is quite low (60–70%), the waste being used for fodder. Although pure buckwheat flour is sometimes used for baking bread, the absence of gluten prevents the dough from rising. It is popular for use in mixtures with wheat, barley or rye flour to improve the taste and nutritional value of bread and other foodstuffs. Up to 30% of buckwheat flour may be mixed in wheat dough for baking bread. In the Himalaya buckwheat is processed into alcoholic drinks.
The seed is also fed to animals, especially pigs and chickens, and buckwheat is sometimes considered a fodder crop rather than a food crop, e.g. in southern Africa. The plants are occasionally used for silage, but must be mixed with other fodders. The tender shoots make a palatable green leaf vegetable. Honeybees in buckwheat fields produce a dark-coloured fragrant honey. The fruit hulls are used as litter in poultry houses, for stuffing pillows, as fuel or for compost. Buckwheat is grown as green manure and cover crop, e.g. in Uganda.
Fresh leaves and inflorescences are used for industrial extraction of rutin, which is applied to strengthen the inner lining of blood vessels (however, it is rather the related species Fagopyrum tataricum (L.) Gaertn., which is commonly grown for rutin production). Rutin is also industrially used as a natural pigment, antioxidant, stabilizer, food preservant and absorber of UV light. In East Africa leaves are chewed or its juice is drunk against fever.
Production and international trade
According to FAO estimates, the average world production of buckwheat seed in 1999–2003 amounted to 2.7 million t/year from 2.7 million ha. The main producing countries are China (1.4 million t/year from 980,000 ha), the Russian Federation (600,000 t/year from 930,000 ha) and Ukraine (320,000 t/year from 440,000 ha). Buckwheat is mainly commercialized locally. Average world export of buckwheat was only 160,000 t/year in 1998–2002, with as main exporter China (104,000 t/year). No production or trade statistics are available for tropical Africa. At present, buckwheat is regaining some importance in Western countries because of its excellent nutritional qualities. In Brazil, Canada, the United States and South Africa buckwheat is grown as an export crop on highly mechanized farms.
Properties
The composition of buckwheat seed per 100 g edible portion is: water 9.8 g, energy 1435 kJ (343 kcal), protein 13.3 g, fat 3.4 g, carbohydrate 71.5 g, dietary fibre 10.0 g, Ca 18 mg, Mg 231 mg, P 347 mg, Fe 2.2 mg, Zn 2.4 mg, thiamin 0.10 mg, riboflavin 0.43 mg, niacin 7.0 mg, vitamin B6 0.21 mg, folate 30 μg and ascorbic acid 0 mg. The essential amino-acid composition per 100 g edible portion is: tryptophan 192 mg, lysine 672 mg, methionine 172 mg, phenylalanine 520 mg, threonine 506 mg, valine 678 mg, leucine 832 mg and isoleucine 498 mg. The principal fatty acids are per 100 g edible portion: oleic acid 988 mg, linoleic acid 961 mg and palmitic acid 450 mg (USDA, 2005). Whole buckwheat fruits are rich in fibre, the hull providing most of it. Stored flour may become rancid because of the high fat content. Buckwheat differs from true cereals in the high biological value of the protein, caused by the high content of essential amino acids, in particular lysine. Due to the absence of gluten, buckwheat is suitable for the diet of people with coeliac disease. On the other hand, buckwheat seed is considered to be one of the most important food allergens. It also contains compounds which can cause irritating skin disorders (‘fagopyrism’) mainly in sheep and pigs and occasionally in humans in case of heavy consumption and exposure to sunlight. Fagopyrism has also been observed in humans after consumption of buckwheat honey. It may also affect cattle when fed pure buckwheat silage.
The flavonoid rutin is present in all aboveground plant parts (leaves, stems, inflorescence, fruit). It has antioxidative, anti-inflammatory and antihypertensive activity; it strengthens the inner lining of blood vessels, reduces cholesterol levels, protects the blood vessels from rupturing, and blood from forming clots.
Botany
Erect annual herb up to 120 cm tall with angular, hollow stem. Leaves alternate, simple and entire; stipules fused into a tubular, short, truncate ocrea; petiole up to 10 cm long in lower leaves, upper leaves almost sessile; blade triangular, hastate or cordate, 2–10 cm × 2–10 cm, acute, 5–7-veined from the base. Inflorescence an axillary or terminal cluster of flowers combined into false racemes. Flowers bisexual, regular, small, rose-red to white, heterostylous; pedicel slender; tepals 5, 3–4 mm long, persistent; stamens 8, alternating at the base with 8 honey glands; ovary superior, 1-celled, trigonous, with 3 styles ending in head-shaped stigmas. Fruit a 3-sided nutlet, 5–7.5 mm × 3 mm, sometimes winged, grey-brown, dark brown to almost black, 1-seeded. Seed pale green turning reddish brown, slightly smaller than fruit.
Fagopyrum comprises about 15 species most of them from eastern Asia. Harpagocarpus, comprising a single species, Harpagocarpus snowdenii Hutch. & Dandy from Central and East Africa, is closely related and should possibly be included in Fagopyrum. Numerous landraces and cultivars of Fagopyrum esculentum are known, differing in fruit shape, adapted to summer or winter cultivation and comprising special-purpose types for grain, fodder, vegetable or medicine.
At soil temperatures above 10°C the seed germinates fast, and seedlings emerge within 7 days. The crop grows fast, reaching the full height of 60–100 cm in 4–6 weeks. Flower formation starts 20 days after emergence, anthesis starts a week later and continues until complete senescence and death of the whole plant. Buckwheat is self-incompatible. Cross-pollination occurs by insects, mostly bees and flies. After the onset of flowering, the vegetative organs (leaves and stems) continue to grow while fruits develop, hence seed ripening is very uneven. From the middle of the flowering period onwards, when the leaf area has reached its maximum, further growth of vegetative organs is slow, and the seed becomes the main sink for assimilates. The seed is ready for harvesting 70–130 days after emergence, depending on cultivar and ecological conditions.
Ecology
Buckwheat is a crop of temperate and subtropical areas, but may be grown successfully at higher elevations in the tropics. In Ethiopia it is grown at about 1500 m altitude. Exact data on optimal temperatures for buckwheat cultivation are scarce, but climate descriptions indicate a range of 18–30°C for day temperatures, and night temperatures 5–10°C lower. Because the leaf mass dries slowly, a dry period is required at maturity and harvest. Buckwheat is very sensitive to frost. Strong winds cause lodging during crop growth and seed shattering at maturity. Buckwheat is rather sensitive to drought because of its poorly developed root system. During flowering, drought combined with high temperatures will cause poor seed set. Much rain during the crop cycle stimulates vegetative growth, but inhibits seed setting, also because it hampers pollination by insects. Buckwheat cultivars are either day-neutral or short-day plants.
Buckwheat performs best on nitrogen-poor light sandy soils, from neutral to rather acid (pH 4.5–7). It is suitable for newly cleared infertile land, drained marshland, rough land or acid soils with a high content of decomposing organic matter. Buckwheat has the reputation of producing an acceptable yield on marginal, infertile land. On wet soils or soils rich in nitrogen, luxuriant growth leads to lodging, poor fruit set, considerable losses during harvest, and thus reduced yields. When used for silage or as green manure, a low seed yield is unimportant, and more biomass will be produced on wetter, heavier soils.
Management
Buckwheat is propagated by seed. The 1000-seed weight is 12–35 g, averaging about 22 g. Before sowing, the seedbed should be finely crumbed. A firm soil at about 5 cm depth reduces drought injury and lodging. Very crusted land and heavy clay soil will result in poor field emergence. Most growers use farm-saved seed. In mechanized cultivation, seed is drilled in rows about 30 cm apart, at a depth of 2–4 cm, requiring 40–60 kg of seed per ha. The crop compensates for a thin stand by branching more. Thin stands produce more inflorescences and seeds per plant. In manual cultivation, seed is broadcast, followed by harrowing to cover the seed with topsoil. Broadcasting requires 10–20 kg seed more per ha than row drilling. Buckwheat is a crop with a short growing season, easily fitting in cropping patterns with cereals, root crops, pulses, and forages. It is sometimes intercropped with vegetables.
Buckwheat competes well with most weeds, but some fast-growing weeds can be a problem. Some growers sow more densely on purpose, and then weed mechanically by harrowing about 4 weeks after emergence, killing most weed plants together with a number of buckwheat seedlings.
The uptake of minerals per ha for a seed yield of 2 t/ha is about 45 kg N, 10 kg P and 50 kg K. Growers usually apply no organic manure and no or little chemical fertilizer, e.g. 10–30 kg N, 0–15 kg P and 15–30 kg K. Only P and K fertilizers should be applied if there is a risk of lodging. In crop rotations with buckwheat, any crop is suitable as preceding crop provided that it does not leave much nitrogen or weed infestation.
Many fungal diseases have been recorded to affect buckwheat, but they only occasionally cause serious damage. Downy mildew (Peronospora sp.), powdery mildew (Erysiphe polygoni) and Rhizoctonia root rot (Rhizoctonia sp.) are the major ones. Cultivars differ markedly in susceptibility. Several viral diseases have been recorded, but they do not cause much damage. Insect damage is rare, but grasshoppers, bean weevils, cutworms, aphids, grain moths and storage beetles may feed on the crop. The worst problem for buckwheat production is damage by birds at maturity and after harvest, when the crop is left to dry in the field. Rats are also sometimes destructive.
When most (at least 75%) seed is mature and most leaves have yellowed and dropped, the crop is harvested by mowing, after which the stems are bundled and put in heaps to dry. Farmers prefer to harvest early in the morning or late in the afternoon, or even at night, when the plants are slightly damp from dew, to reduce grain shattering. The bundles are stacked alternately head-to-tail in the heaps, to reduce bird damage. If the leaves are not dry enough, they may stick together, causing problems for threshing. Combine harvesting is practised in more industrialized countries.
Seed yields normally vary from 0.6–2.5 t/ha, but 3 t/ha is occasionally obtained. Research has not succeeded in raising yields of buckwheat; they remain about the same as a century ago.
Thorough drying to a moisture content below 16% facilitates the removal of straw fragments and immature seed. Small farmers usually thresh manually. Mechanical threshing requires careful regulation of the threshing cylinder to avoid damaging the seed. Processing starts with hulling and separation of the hulls from the groats, followed by milling. Formerly, processing was done by individual households or in small village workshops. At present, most buckwheat is processed in factories that apply advanced food technology to make specific foodstuffs.
Genetic resources and breeding
The largest collections of buckwheat germplasm are held in the Russian Federation (N.I. Vavilov All-Russian Scientific Research Institute of Plant Industry, St. Petersburg, 2010 accessions), China (Institute of Crop Germplasm Resources (CAAS), Beijing, 1495 accessions) and Canada (Agriculture Canada Research Station, Morden, Manitoba, 570 accessions). Germplasm is also available in national collections in the United States, South Africa, Japan, Korea, India, Pakistan, Nepal, Slovenia, Poland and Germany. All these countries are part of a network under the International Plant Genetic Resources Institute (IPGRI), responsible for characterization and documentation. There are numerous landraces and many have already been collected for selection, testing and storage in genebanks. Buckwheat is not threatened by genetic erosion.
Breeding of buckwheat has been carried out in, for example, the United States, Russia, Japan, India and former Yugoslavia. Uniform, highly self-compatible diploid lines have been isolated. They revealed a severe inbreeding depression, and heterosis in F1 generations. Breeders have selected improved cultivars with higher yields, e.g. by improving the plant habit (shorter stems with reduced liability to lodging). Autotetraploid buckwheat selections show superior characters in many aspects (self-fertile, higher rutin content, increased dry matter production, improved nitrogen uptake, no seed shedding). Improvement is also expected from breeding programmes with close relatives of buckwheat such as Fagopyrum tataricum (L.) Gaertn. (Tatary buckwheat) and Fagopyrum homotropicum Ohnishi, e.g. to increase the rutin content and to increase self-compatibility. Somatic embryogenesis of buckwheat is possible using immature embryos, protoplasts, cotyledons, hypocotyls, leaf segments or stem segments as explants.
Prospects
Internationally, the interest in buckwheat as a health food is increasing. With a higher price compensating for the lower yield level compared to cereals, the acreage under buckwheat may increase. It is potentially an interesting crop for marginal land in highland areas in Africa, especially as a low-input subsistence or cash crop in rotation with other crops. An interesting feature is that at the moment buckwheat is hardly affected by diseases and pests. The main disadvantages of the crop are lodging, seed shattering and low yields. Given the existing genetic variability, it is likely that breeding will result in cultivars better adapted to tropical conditions, with less lodging and seed shattering, and improved seed set, hence with higher yield levels.
Major references
• Biacs, P., Aubrecht, E., Léder, I. & Lajos, J., 2002. Buckwheat. In: Belton, P.S. & Taylor, J.R.N. (Editors). Pseudocereals and less common cereals: grain properties and utilization potential. Springer Verlag, Berlin, Germany, pp. 123–151.
• Campbell, C.G., 1997. Buckwheat. Fagopyrum esculentum Moench. Promoting the conservation and use of underutilized and neglected crops 19. Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany / International Plant Genetic Resources Institute, Rome, Italy. 94 pp.
• Grubben, G.J.H. & Siemonsma, J.S., 1996. Fagopyrum esculentum Moench. In: Grubben, G.J.H. & Partohardjono, S. (Editors). Plant Resources of South-East Asia No 10. Cereals. Backhuys Publishers, Leiden, Netherlands. pp. 95–99.
• Ohnishi, O., 1998. Search for the wild ancestor of buckwheat 3. The wild ancestor of cultivated common buckwheat, and of tatary buckwheat. Economic Botany 52(2): 123–133.
• Zeller, F.J. & Hsam, S.L.K., 2004. Buchweizen - die vergessene Kulturpflanze. Biologie in Unserer Zeit 34(1): 24–31.
Other references
• Edwardson, S., 1996. Buckwheat: pseudocereal and nutraceutical. In: Janick, J. (Editor). Progress in new crops. Proceedings of the third national symposium new crops - new opportunities, new technologies, Indianapolis, Indiana, October 22–25, 1996. ASHS Press, Alexandria, Virginia, United States. pp. 195–207.
• Gumerova, E.A., Galeeva, E.I., Chuyenkova, S.A. & Rumyantseva, N.I., 2003. Somatic embryogenesis and bud formation on cultured Fagopyrum esculentum hypocotyls. Russian Journal of Plant Physiology 50(5): 640–645.
• Hedberg, O., 2000. Polygonaceae. In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 2, part 1. Magnoliaceae to Flacourtiaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 336–347.
• Joshi, B.D. & Rana, R.S., 1995. Buckwheat (Fagopyrum esculentum). In: Williams, J.T. (Editor). Cereals and pseudocereals. Underutilized crops series. Chapman & Hall, London, United Kingdom. pp. 85–127.
• Kim, K.H., Lee, K.W., Kim, D.Y., Park, H.H., Kwon, I.B. & Lee, H.J., 2005. Optimal recovery of high-purity rutin crystals from the whole plant of Fagopyrum esculentum Moench (buckwheat) by extraction, fractionation, and recrystallization. Bioresource Technology 96(15): 1709–1712.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Ohnishi, O. & Asano, N., 1999. Genetic diversity of Fagopyrum homotropicum, a wild species related to common buckwheat. Genetic Resources and Crop Evolution 46(4): 389–398.
• Sohn, M.H., Lee, S.Y. & Kim, K.E., 2003. Prediction of buckwheat allergy using specific IgE concentrations in children. Allergy 58(12): 1308–1310.
• USDA, 2005. USDA national nutrient database for standard reference, release 18. [Internet] U.S. Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory, Beltsville Md, United States. http://www.nal.usda.gov/fnic/foodcomp. Accessed August 2005.
• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
Sources of illustration
• Grubben, G.J.H. & Siemonsma, J.S., 1996. Fagopyrum esculentum Moench. In: Grubben, G.J.H. & Partohardjono, S. (Editors). Plant Resources of South-East Asia No 10. Cereals. Backhuys Publishers, Leiden, Netherlands. pp. 95–99.
Author(s)
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Based on PROSEA 10: ‘Cereals’.

Editors
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
G. Belay
Ethiopian Agricultural Research Organization, Debre Zeit Center, P.O. Box 32, Debre Zeit, Ethiopia
Associate editors
J.M.J. de Wet
Department of Crop Sciences, Urbana-Champaign, Turner Hall, 1102 South Goodwin Avenue, Urbana, IL 61801, United States
O.T. Edje
Faculty of Agriculture, University of Swaziland, P.O. Luyengo, Luyengo, Swaziland
E. Westphal
Ritzema Bosweg 13, 6706 BB Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Jansen, P.C.M., 2006. Fagopyrum esculentum Moench In: Brink, M. & Belay, G. (Editors). PROTA 1: Cereals and pulses/Céréales et légumes secs. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, flowering branch; 2, flower; 3, unwinged fruit; 4, winged fruit; 5, top view of winged fruit.
Source: PROSEA