Grass pea (Lathyrus sativus L.) is an important crop in Ethiopia. Its vital importance in the Ethiopian agriculture emanates from its resistance to drought, salinity, waterlogging and low soil fertility. However, low levels of the amino acids methionine and tryptophan and the presence of the neurotoxin β-N-oxalyl-L-α,β-diaminopropanoic acid (ODAP) in the seeds are the major limitations of the crop. Genetic improvement of grass pea in Ethiopia has been started in the 1960s at Holetta Agricultural Research Center. The major objectives of the grass pea research were to develop and promote high-yielding cultivars with low ODAP content coupled with improved management production packages. However, the 50 years of on-station and on-farm research was not successful in producing outstanding varieties with the desired traits. Compared to other grain legumes, the poor success of varietal development endeavours within the context of grass pea improvement philosophy is typically related to the failure of the conventional breeding approach to fix a zero or low ODAP content because this trait is highly influenced by climatic and edaphic environment.
That’s the abstract of the Plant Breeding paper “Genetic improvement of grass pea (Lathyrus sativus) in Ethiopia: an unfulfilled promise” by Dejene Girma and Lijalem Korbu. ((Girma, D., & Korbu, L. (2012). Genetic improvement of grass pea (Lathyrus sativus) in Ethiopia: an unfulfilled promise Plant Breeding DOI: 10.1111/j.1439-0523.2011.01935.x)) You may remember it as the one I summarized in yesterday’s Brainfood as: “Conventional breeding for low ODAP hasn’t worked, so forget about solving that problem through conventional breeding, and move on to other problems, or use genetic transformation.”
I took the liberty of running the paper by a few experts to get a bit of a more rounded assessment. This is what Dr Dirk Enneking, legume breeder and frequent commenter here, had to say:
The challenge is to develop high yielding grasspea crops regardless of ODAP content, while ensuring that the people who, sooner or later, will be forced to subsist on an almost exclusive diet of grasspea know what they need to do to detoxify the seed prior to consumption. They also need the means to dilute their diet with other food, containing sufficient sulphur amino acids, to prevent toxicity. There is a need for an animal model of neurolathyrism to scrutinise such an approach by experiment. Further details: Special issue March 2011 Food and Chemical Toxicology.
One first practical step to prevent neurolathyrism might be the identification and education of those most at risk, the human grasspea consumers, usually the poorest of the poor, often in remote villages, in areas where grasspea is used as a food. They do not necessarily look malnourished, so conventional nutritional surveys easily miss them. Once they are identified they can be targeted with specific interventions: a) to alleviate their poverty, b) education, c) during famines with food aid. Considering an area of ca. 150 000 ha of grasspea production in Ethiopia and trade of the crop as seed or in split form in markets, [unfortunately not part of current donor funded routine market monitoring programs] the task of locating grasspea consumers is quite manageable in that country.
So Dirk agrees on the advisability of moderating the obsession with low-ODAP breeding. Dr Tadesse Wuletaw, who worked on Lathyrus breeding in Ethiopia and is now at ICARDA, has a somewhat different take.
This is a good review. I do agree on the importance of molecular/biotech approaches in grasspea breeding. However, the shift in focus from ODAP to improving other proteins would be misleading. Especially in countries like Ethiopia where grasspea is principally grown for human consumption, the focus should remain on the development of toxin free lines. Though this is a huge task… I see possibilities through interspecific hybridization and transformation. Mutation breeding would also help especially by using combination of physical and chemical mutagens (personal experience).
Dr Ahmed Amri is the head of the ICARDA genebank, one of the best sources of Lathyrus diversity. He agrees on the possible role of wild relatives in breeding for low ODAP, and points to some (possibly temporary?) successes.
I would like also to inform you that ICARDA has developed in late 1990’s somaclonal variants with low ODAP. I still think that the rate of outcrossing detected in grasspea could revert them back to percent of ODAP higher that the threshold when growing low-ODAP varieties for several generations. This is an area which can also be handled through research. There are some Lathyrus species within the genepool 2 which are free from ODAP such as L. tangitanus which could be used in interspecific crosses. Related to breeding for high yield in grass pea mainly grown under harsh conditions might not be the priority as this potential will never be expressed. Breeding for low ODAP and for tolerance to Orobanche are urgent breeding objectives.
And finally, here is ICARDA’s senior Lathyrus breeder Dr Shiv Kumar Agrawal. He also points to some successes of conventional breeding, while not minimizing their ambiguities. He sees great promise in new methods too.
Thanks for sharing this review. I do agree with the reviewers that breeding success in Lathyrus is not as apparent as we see in other crops. One has to see also how much breeding efforts were directed to this crop in spite of its importance in climate change scenario. In India, efforts were made, resulting in successful release of very low ODAP varieties (Ratan, Prateek and Mahateora) using conventional breeding methods. All these cultivars with 0.07% ODAP over the years are grown by farmers. Let me make it clear that in India, there is no ban on research and cultivation of Lathyrus. There is a ban on trade in some states but at the same, it is officially traded in some states like Maharashtra. This year, we have released one Lathyrus variety BARI Khesari-3, an ICARDA line in Bangladesh. This variety has also shown below 0.1% ODAP over the years.
At ICARDA, we evaluated 260 somaclones to assess variability for ODAP besides generation of second cycle somaclones from low and high ODAP lines. Influence of environmental factors particularly water stress on ODAP content is substantial. At the same time, low ODAP lines remain low in ranking (we are in the process of preparing a manuscript from our work on this aspect). At present at ICARDA, we employ mutation, tissue culture and inter-specific hybridization along with our conventional breeding methods using genetic variability for ODAP in our germplasm. Results are encouraging. New tools including transformation are useful for directed improvement in reducing ODAP content. However, the concern of environment effect and outcrossing will still be the issues.
The variety Wasie which was released in Ethiopia from ICARDA material, when estimated for ODAP, has below 0.1% ODAP over the years of testing. We will get seeds of Wasie from Ethiopia and test it for the genetic purity along with our original seeds.
Dr Agrawal has kindly provided a clipping from an Indian newspaper discussing grasspea breeding in that country. It is clearly not the case, as I’ve occasionally heard it suggested, that there is a prohibition on breeding of this crop in India, although Dr Agrawal implies that it is seriously under-funded.
We’ll investigate the possibility of getting these reactions to the authors, to see if they’d like to respond. In the meantime, if you would like to contribute to the debate, do comment below.
I did some research on grasspea in the 1980s (with AG Yunus), establishing the genepools of Lathyrus sativus, so I do not underestimate the difficulties of wide crosses. While many might perceive grasspea to be a so-called ‘minor crop’, its importance for so many poor people does warrant the efforts that are being made to increase its productivity. I’ll follow this work with interest.
I respect the authors for trying to put new live into Lathyrus sativus research and for questioning why two generations of efforts did not result in what has been achieved in other crops.
I do hope that this conversation can reinstate some dignity to the plant Lathyrus sativus. I personally resent its status of toxic plant. Like all legumes, grass pea is low in sulphur containing amino acids methionine and cysteine and is not a well balanced food. However, unlike other legumes, grass pea is consumed as a staple during food insufficiency, especially during or after droughts, when grass pea, by virtue of its tolerance to adverse climatic conditions, can be the only food affordable by the very poor.
From epidemiological surveys in Ethiopia and Bangladesh, it seems clear that neurolathyrism only occurs when three conditions are present: i) extreme poverty of the producers of grass pea, ii) the consumers are mostly illiterate, and iii) grass pea is the cheapest food available. When there is no market where the producer can sell the grass pea at an interesting price, he or she can not afford a better balanced diet than grass pea as a staple or even as an exclusive food. Poor soil and drought can aggravate these conditions as this would select grass pea over other crops less resistant to such conditions.
In Bangladesh the price of grass pea was lowest of all commercial foodstuffs during the last epidemic of neurolathyrism. Even though the production of grass pea has increased in Bangladesh, there are no new reports of neurolathyrism in the country. The price of grass pea is now about double of the price of rice, and hence overconsumption of grass pea as the cheapest food is no longer a risk for the poor.
Over-emphasis on the study of ODAP has contributed to give grass pea the status of toxic plant, while the real cause of neurolathyrism is probably a combination of oxidative stress and the presence of ODAP. Over-consumption of other legumes deficient in sulphur amino acids, or roots such as cassava, may have similar consequences.
Only considering the content of ODAP in seeds growing in optimal experimental conditions is not the correct way to evaluate the value of a variety of grass pea. The environmental effects on yield and ODAP level have been studied by Asnake Fikre, and especially on the poor volcanic soil of Ethiopia, the ODAP content can go much higher than in laboratory conditions.
(Asnake Fikre et al. (2011) Climatic, edaphic and altitudinal factors affecting yield and toxicity of Lathyrus sativus grown at five locations in Ethiopia. Food and Chemical Toxicology 49, 623-630. doi:10.1016/j.fct.2010.06.055 )
On the other hand, Getahun has studied a number of factors influencing the incidence of neurolathyrism during the recent epidemic in Ethiopia, and found that balancing the grass pea diet with at least one third of cereals, or with condiments with antioxidant capacity such as onion, garlic and ginger are protective factors. (Getahun (2003) Food-aid cereals to reduce neurolathyrism related to grass-pea preparations during famine. Lancet 362, 1808-1810.)
Experiments with young chicks, receiving a grass pea diet, demonstrated the protective effect of methionine to greatly reduce the neurological symptoms, although these are different from human neurolathyrism. (Fikre et al. (2010) Effect of methionine supplement on physical responses and neurological symptoms in broiler chicks fed grass pea (Lathyrus sativus)-based starter ration. Food and Chemical Toxicology 48, 11–17.)
A recently identified risk factor for neurolathyrism is stress. Experimental animals receiving daily injections of ODAP had a 3 times higher incidence of neurological symptoms when the young animals were put under stress. (Kuniko Kusama-Eguchi et al. (2010) Hind-limb paraparesis in a rat model for neurolathyrism associated with apoptosis and an impaired vascular endothelial growth factor system in the spinal cord. The Journal of Comparative Neurology 518, 928-942. DOI: 10.1002/cne.22257)
This effect of stress may explain the extremely high incidence of neurolathyrism among the inmates of a WW II labor camp in Vapniarka. Stress may also have played a role during the civil war in Spain, or in the maquis in Greece during the war, when cases of neurolathyrism occurred. It also may play a role among the poor and illiterates of low socio-economic status during famines in Ethiopia.
All this to explain that in a normal diet grass pea can be even a daily component that gives no risk to the consumer as long as he does not use it as the main source of calories during extended periods. Long periods of a methionine and cysteine deficient diet can exhaust the reserves of glutathione and increase oxidative stress. Stress may also affect the integrity of the blood/brain barrier that in a healthy person protects the central nervous system from toxic metabolites in the bloodstream, including ODAP after grass pea consumption.
To further question the bad reputation of grass pea and its metabolite ODAP, a Chinese group has obtained a patent for the use of ODAP as haemostatic during surgery.
ODAP is also present in the longevity promoting Ginseng root, where under the name of Dencichine it is known for its haemostatic property, to stop bleeding. In China it is even included in some brands of toothpaste.
I do hope this is helpful for promoting a less narrow-sighted view on grass pea. It is time to finally remove the ODAP blindfold from Lathyrus research, and also consider positive aspect such as the very high nitrogen fixation and the potential role of ODAP in this. The presence of homo-arginine in grass pea is hardly mentioned, while it can have a positive effect on cardiovascular health. The effect of regular moderate consumption of grass pea on longevity should be a priority in epidemiological research.
Prof. Lambein,
Thanks for your view in grass pea. I’ve been working on improvement of this crop for the last 14 yrs, and keenly following you at Ghent. You will be glad to know that Functional Plant Science and Biotechnology is going to develop a special issue on grass pea, and I’ll contact you very soon. It is also a grand news that National institute of Nutrition (NIN) at Hyderabad, India on NOV 9-10, 2012 is organizing an international conference on grass pea research strategy, indicating India at last is recognizing importance of grass pea. Also, leading Indian newspapers are now allotting space for grass pea.
Thanks a lot for your comments. I’ll contact you very soon
Warm regards,
Dr. Dibyendu Talukdar
Calcutta, India
I am glad that Lathyrus researchers are getting bold and gradually coming to grips with realities. Neurolathyrism (grass pea toxicity) can in fact be aptly described as a disease thrust on the poor by the Society. Drs Girma and Korbu have rightfully admitted that 50 years of research haven’t been successful. All that was needed in all these years was a simple advocation of avoiding grass pea as a staple diet and use it as a pulse should be. This could have changed the whole scenario. I wonder if any studies have been done at any time by feeding only pulses as a sole diet!
Looking at the likely benefits of Homoarginine on the cardiovasculature and emerging concepts on ODAP itself I am of the firm belief that grass pea in coming years will turn into a rich man’s pulse. I find more and more of research interests growing on these two amino acids and future should concentrate not only on grass pea but lathyrus species in general.
Dear Prof. Rao,
Thanks for your relentless effort to put grass pea in a respected cuisine realizing the basic problem here in India. You will be glad to know that Functional Plant Science & Biotechnology is going to develop a special issue on grass pea, and I’ll contact you very soon to share your vast experience on Lathyrus.
May I request you to send your current mail address/contacts
warm regards,
Dr. Dibyendu Talukdar,
Calcutta, India
Prof SLN Rao is the most eminent authority on ODAP since he has discovered it!
My view on this happend fact is that the world couldnot take or wouldnot like to take multi-step/agregates of solutions for one. Clearly the process of neurolathyrism has long been proposed and many scholars tried to sort out critical predisposing conditions and the mangment. Non the less still grass pea is in a blame and would be so, but it survives all pressures from social, environmental and other diamentions. Right now we have the solution for neurolathyrism, tell targets how to use!!!