blossoming treasures of biodiversity 14. grass pea (lathyrus sativus) can a last resort food become...

7/30/2019 BLOSSOMING TREASURES of BIODIVERSITY 14. Grass Pea (Lathyrus Sativus) Can a Last Resort Food Become a Firs

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BLOSSOMING TREASURES OF BIODIVERSITY:

14. Grass Pea (Lathyrus sativus)Can a last resort food become a rst choice?

E. Small and P.M. Catling

authors addres

E. SmallP.M. CatlingBiodiversity,National ProgramEnvironmental HeAgriculture andAgri-Food CanadaOttawa, Ontario,Canada K1A 0C6

[email protected]@agr.gc.c

S P E C I E S B Y S P E C I E S

This past contribution from our series BLOSSOMING TREASURES OF BIODIVERSITY[Biodiversity5(4) 2004]has been chosen for presentation in this special issue on Food & Agriculture because it illustrates several importantaspects of new crop development. First, it demonstrates the importance of crop research: in this case, millionsof people forced by famine to consume a nutritious but toxic food can be spared agonizing paralysis by researchaimed at developing new cultivated varieties with low levels of paralytic neurotoxin. Second, it shows that the benefitsfrom crop research are usually not limited to the original target audience: in this case, not only has agriculture insubtropical countries benefitted by the creation of new cultivars useful for humans, but temperate region agriculturehas also received new cultivars suitable as forage and fodder for livestock. Third, the cultural difficulties involvedin implementing the benefits of non-toxic cultivars reminds us that the popularization of new crops often requiresconsideration of not only scientific and economic aspects, but also social constraints.

Poisonous? Yes! Despite the friendly name Sweet Pea, thewell known, attractive garden ornamental Lathyrus odoratusshown here is toxic. It has a devastatingly poisonous relative,the Grass Pea, featured in this article. This illustration is fromCurtis, W. (Editor). 1787. The Botanical Magazine, Vol. 1,Plate 160. London, United Kingdom.


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with 36 seeds. The seeds are often white, brownish-grey, or lightcream in color, and may also be speckled with black. The seedsare distinctively wedge shaped, and range in size from 37 mm(1/81/4 inch) in diameter. Grass Pea probably originated fromthe Mediterranean area and/or western Asia.

fOOD use

The use of Grass Pea for human food may date back 8,000years in the region of the Balkan Peninsula. From the

eastern Mediterranean, Grass Pea was taken to Africa, Asia,and Europe (where it may well have been one of the rstdomesticated crops). It has been grown for thousands ofyears, but at present is a major food crop of India, Pakistan,

Bangladesh, Nepal, and Ethiopia. Grass Pea is raised byseveral hundred million farmers in the Indian subcontinentand sub-Saharan Africa. In India, 2 million ha (5 millionacres) are under cultivation.

The seeds are roasted, made into soup, and prepared as pasteballs. Flour or meal from Grass Pea can be used in cooking or

to make bread. In Asia the leaves are sometimes eaten as a pot

Imagine a food crop that has permanently crippled millions ofpeople. The Grass Pea is widely consumed in Asia and Africa,

with tragic results. Yet, this remarkable poisonous plant notonly has the potential to safely feed much of the world, but alsois extraordinarily benecial to the environment in comparisonwith most other crops.

tHe PlAnt

The Pea in Grass Pea is based on resemblance to the

Garden Pea (Pisum sativum). Both are members of the legumefamily. The grass in the name refers to its leaets, whichare long and grass-shaped. Grass Pea (alternatively spelledGrasspea) is known by many other names, including BlueVetchling, Chickling Pea, Chickling Vetch, Dogtooth Pea, GrassPeavine, Indian Pea, Riga Pea, and Wedge Peavine. Non-Englishnames include Batura (India), Khesari (Bangladesh and India),Guaya (Ethiopia), Gilbin (Sudan), and Matri (Pakistan).This annual herb has white, pink, red, purple, or blue owers, and

grows as a suberect, creeping, or climbing vine, typically from0.61 m (23 feet) in length, although forms are known that reach9 m (30 feet). The pods are at, 2.55 cm (12 inches) in length,

A, Grass Pea. From Curtis, W. (Editor). 1790.The Botanical Magazine, Vol. 3, Plate 115. London, United Kingdom. B, Grass Pea. From Hallier, E.H. 1886. Flora von Deutschland,edition 5 (of publication originally authored by D.F.L. von Schlechtendal et al.). Volume 5, Plate 2508. F.E. Khler, Gera-Untermhaus, Germany.

A B


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herb and the immature pods boiled as a vegetable. Grass Pea isnot currently a food of Western nations, but with present effortsto create completely non-toxic lines, it may become an important

Western crop.

Grass pea also feeds millions of people worldwide as aconsequence of its use as a fodder, especially for cattle in partsof south-central Europe, as well as Africa and Asia. Some of

the extensive variation in the species, including wide-leavedforms, is thought to be a result of selection for forage. Recently,improved fodder varieties have been developed in Canada.

The plant is exceptionally capable of withstanding drought and,as a result, is often the cheapest or only food available to thepoor. Moreover, the seeds typically contain over 25% protein(sometimes as high as 32%), and are often the only proteinavailable in poor regions. This is the source of an extreme health

problem called lathyrism, described below.

lAtHyrisM

To survive famine, people are sometimes compelled to eat

poisonous Grass Pea seeds. The amount of poison can bereduced by soaking, or boiling with changes of water. Bakingand roasting also reduce the toxin. While these methods canlower the neurotoxin content by over 90%, the nutritionalquality is also lowered and some water-soluble vitamins arelost. Tragically, poor people simply lack enough water andfuel to carry out such treatments to make the Grass Pea less

poisonous.

For many, the result of eating too much toxic seed is a conditioncalled lathyrism (neurolathyrism), characterized by irreversible,

crippling, lameness. It usually occurs when Grass Pea hasmade up more than one-third of the diet for 3 or 4 months.Lathyrism is said to strike below the belt. When too much GrassPea is consumed, both legs become paralysed and degeneratepermanently. The onset of the disease is often sudden. Continuedconsumption can result in convulsions and nally death. At least100,000 people in developing countries are believed to sufferfrom the disease. Toxicity does not affect everyone equally.

Some people are seriously disabled, others are not affected.For reasons that are not fully understood, paralysis is more

common among males than females. People between 20 and29 years of age have been the predominant group affected.Young men under 40 are particularly susceptible. Within socialclasses lathyrism is especially prevalent among poorer unskilledlabourers who have less food options. Among livestock, horsesare notably sensitive.

tOxic PrinciPle

Lathyrism is caused by an amino acid in the seeds of GrassPea. There is no simple name for this toxic amino acid. It has

been called beta-N-oxalyamino-L alanine (BOAA for short),beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (Ox-dapro orODAP for short), and L-3-oxalyamino-2-amino-propionic acid(OAP for short). This amino acid is not one of the 20 amino acidsthat form the basis of proteins that are necessary for human life.It is a neurological poison that destroys nerves in both humansand livestock. The poisonous amino acid may be present in aconcentration of up to 2.5% in the seeds. Water stress can doublethe toxin level, while salinity in the soil may reduce the toxin level

in the seeds. It has been suggested that human consumption isconsidered to be safe at levels below 0.2% of the toxin.

A, Grass Pea seed for sale in a market in India ; B, Low-toxin seeds of Grass Pea, bred in Canada (photographs courtesy of Dr. C.G. Campbell).

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human consumption, the remaining parts of the plant areavailable to feed livestock, mostly cattle, and in this way GrassPea can further contribute to efcient utilization of its biomass.The seeds are sometimes simply broadcast on the soil, withouttillage or with minimum soil disturbance. These practices areconsidered today to be ecologically friendly (for example, notdisturbing soil organisms). Grass Pea is a biodiversity-friendly,efcient crop that contributes to sustainable agriculture becauseit grows well with minimum agricultural inputs (including

fertilizer, water, pesticides, and herbicides).

cliMAtic ADAPtAtiOn

Grass Pea is a cool season crop of warm-temperate (Mediterranean)and subtropical regions. It is naturally adapted to the arid or semi-arid conditions prevailing in much of southern Asia during thewinter season. Accordingly, in subtropical arid regions, notablyin China, South Asia, the Middle East, and North Africa, it isoften raised as a winter crop. Remarkably, the plant is alsoadapted to growing under waterlogged conditions. It grows wellin some areas where monsoon rains or seasonal ooding canseverely damage other crops, such as in areas of Bangladesh,

Nepal, and Ethiopia. It also thrives when simply broadcast intothe standing water of a rice crop. In temperate regions, GrassPea also grows well, but tends to produce much larger amountsof stems and leaves, rather than seeds, making the crop moresuitable as forage and fodder for livestock rather than for grain.In Southeast Asia, it is often sown as a mixture with other crops,so that if adverse weather reduces the yield of the other crops,

A, Farmer crippled by lathyrism, in the Grass Pea crop that crippled him. The severity of the disease is often judged by whether one or two canes are used.B, Grass Pea breeder Clayton Campbell displaying a forage type ofLathyrus sativus. (Photographs courtesy of Dr. C.G. Campbell).

lOW-tOxin vArieties

In recent decades, several breeders, notably Canadian breederClayton G. Campbell, have created low-toxin varieties (below0.05%). ICARDA (International Center for Agricultural Researchin the Dry Areas) part of the Consultative Group on InternationalAgricultural Research (CGIAR), with headquarters in Aleppo,Syria, announced in 2000 that it had developed plants that are

virtually toxin-free when planted under relatively wet conditions(although toxins are produced as soil moisture falls). Efforts to

solve the lathyrism problem by introducing low-toxin lines havehad limited success to date because of various objections to thecharacteristics of these varieties by the consumers. The problemis in part cultural, and efforts are underway to persuade peopleof the desirability of using low-toxin varieties.

ADAPtAtiOns tO

envirOnMentAlly-frienDly AGriculture

Grass Pea is extraordinarily suited to grow under adverseconditions. It tolerates both drought and ooding very well. Itshardy, penetrating root system is able to grow on a wide range ofsoil types, including very poor soils and heavy clay. Like other

legumes, it hosts nitrogen-xing bacteria in root nodules, andso does not require much nitrogen fertilization. Also like otherlegumes, which fertilize the soil, the Grass Pea is commonlyused in crop rotation, especially with rice in Asia, therebycontributing to long-term sustainable farming. Additionally,the plant is resistant to many pests, including insects thatspecialize on stored grain. After the seeds are collected for

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No sight is more chilling to those of us who have worked

in famine situations than to see South Asian villages where

many of the residents are crawling on their knees and

elbows or are being wheeled about, because of lathyrism.

alan berg [in Food for Life Global, issue #34 June 12,

1999(Web document)].

anew approachto faminereliefA few consecutive droughts in Ethiopia in the 1970s

disabled 70,000 people. In 1999 an estimated 2,000

were crippled in a small part of Ethiopia. That sameyear, a comprehensive plan was developed to eliminate

lathyrism in part of the country using imported alternate

protein sources. Its cost was 3 cents per person per

day. One thousand people could have been protected

from the crippling condition for 1 month for three

thousand dollars. Even this relatively inexpensive plan

was not implemented, like so many other well-intended

plans for famine relief. The effort to produce toxin-free

varieties of Grass Pea is clearly a main hope.

the much hardier Grass Pea provides insurance that enough foodwill be produced for survival.

cOnservAtiOn issues

Although Grass Pea is widely distributed, and there is alreadya considerable number of seed collections in gene banks,there remains an urgent need for additional conservationmeasures. This is because the species is variable and hasnumerous relatives. The genusLathyrus is native to the northernhemisphere, South America, and the mountains of east Africa,and includes about 170 species. Dozens of races ofL. sativus

have been identied in India alone based on differences inower and seed colour and pod markings. There is a needfor analysis and preservation of much of this variation thatpotentially can contribute genes for Grass Pea improvement.Breeders have noted the desirability of iden-tifying ecologicalareas that should be conserved for the specic purpose ofprotecting species and varieties ofLathyrus that are importantfor Grass Pea development.

PriOrities AnD PrOsPects

Grass Pea produces large amounts of good-tasting seeds under

climatic and soil conditions that very few other crops cantolerate. Moreover, it is very ecologically friendly in compa-rison to other crops, and contributes to sustainable agriculture.For a crop that has been exploited by humans for perhaps 8,000years, the extent of domestication (i.e. genetic alteration tosuit the needs of humans) is very limited. Therefore, there isa great opportunity for breeding cultivated varieties to meetthe particular needs of different countries. Although somepromising selections have been made that appear to have

very low levels of the paralytic neurotoxin, the principalgoal remains to improve and employ cultivars that are free oftoxins, as well as having desirable agricultural and commercial

characteristics. Grass Pea has enormous potential for reducinghunger in areas prone to crop failures and resulting famines, aswell as providing new food products for rich nations. Given thatthe crop is also extraordinarily suited to growing with limitedinputs of water, herbicides, fertilizers, and the disturbancesassociated with soil tillage, Grass Pea is certainly amongthe most desirable biodiversity-friendly crops deserving ofdevelopment. Especially important is the potential of Grass

Pea to help meet the global challenges of sustainable wateruse and agricultural production in arid regions.

Believe it Or nOt

l An old practice in India called lagua bonded landless

labourers to wages of Grass Pea seed, but this practicehas been stopped.

l Lentil is the most important food species of the Peafamily in the Old World. Grass Pea often appears as aweedy contaminant of Lentil crops. This observationhas led to the theory that after Lentil was domesticated,Grass Pea seeds evolved to closely mimic the size,shape, and color of Lentil seeds, so that Grass Peawould survive among Lentils and be distributed byhumans as a contaminant wherever Lentil was grown.(For additional information, see Erskine, W., J. Smartt,

and F.J. Muehlbauer 1994. Mimicry of lentil and thedomestication of common vetch and grass pea.EconomicBotany 48: 326332.)

l

Some of our modern crops (e.g. Parsnip, Carrot, Canola,lupine species, and some melon species) have been selected

from wild ancestors that have poisonous constituents toprotect themselves against animals and microorganisms.During domestication, most if not all of the natural toxicchemicals have been removed by selection, and this isbenecial for people, but less so for the plants, whichoften have to be protected with articial pesticides. Oneof the reasons that toxic plants such as Grass Pea and thecyanide-containing Cassava are still cultivated for food indeveloping countries is that they thrive without syntheticpesticides, which are too expensive in poor regions.

Key infOrMAtiOn sOurces:Abegaz, B.M., R.T. Haimanot, V.S. Palmer and P.S. Spencer (Eds) 1994.

Nutrition, neurotoxins, & lathyrism: the ODAP challenge. Proceedings ofthe second internationalLathyrus/lathyrism conference in Ethiopia underthe International Network for the Improvement ofLathyrus sativus andthe Eradication of Lathyrism. Third World Medical Research Foundation,New York, NY. 139 pp.

Asfaw, T., D. Asgelil and H. Bekele 1994 . Genetics and breeding ofgrasspea.In Cool-season food legumes of Ethiopia.Edited by T. Asfaw, B.Geletu, M.C. Saxena, C. Mohan, and M.B. Solh. International Center forAgricultural Research in the Dry Areas, Aleppo, Syria. pp. 183195.

Barrow, M.V., C.F. Simpson and E.J. Miller 1974. Lathyrism: a worldreview. Quart. Rev. Biol. 49: 102128.

Campbell, C.G. 1997. Grass pea, Lathyrus sativus L. International PlantGenetic Resources Institute, Rome, Italy. IPGRI, 92 pp. Available online:http://www.ipgri.cgiar.org/publications/pdf/430.pdf

Smartt, J., A. Kaul, W.A. Araya, M.M. Rahman and J. Kearney 1994.Grasspea (Lathyrus sativus L.) as a potentially safe food legume crop.InExpanding the production and use of cool season food legumes.Edited byF.J. Muehlbauer and W.J. Kaiser. Kluwer Academic Publishers. Dordrecht,The Netherlands. pp. 144155.

Spencer, P.S. (Ed). 1989. The grass pea: threat and promise. Proceedings ofthe International Network for the Improvement ofLathyrus sativus andthe Eradication of Lathyrism and recommendations of the InternationalINILSEL Coordination Committee. Third World Medical ResearchFoundation, New York, NY. 244 pp.

Yusuf, H.K.M., and F. Lambein (Eds). 1995.Lathyrus sativus and humanlathyrism: progress and prospects, from international collaborations.Proceedings of the second international colloquium on Lathry tus/Lathrytism, Dhaka, December 10-12, 1993. University of Dhaka, Dhaka,Bangladesh. 288 pp.

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