Grasspea - a tough choice
Patches of green in a parched desert landscape; during the drought in Georgia two years ago, only one crop was left standing: grasspea, (Lathyrus sativus L.), a legume species capable of withstanding a myriad of assaults, not only drought, but water-logging, cold, and pests and disease attack. As a fodder crop it is both palatable and extremely nutritious, either by direct grazing or by harvesting for grain and straw or hay. It is rich in protein (30%), and for sheep its high lysine content promotes improved wool quality. And, not surprisingly for an adaptable crop suitable for harsh environments, grasspea is easily cultivated, with little need for costly inputs. Originating in south west Asia or southern Europe, and cultivated as a food and forage crop for over 8000 years, grasspea is now a lifeline for millions of poor farmers in Africa, Asia and the Middle East.
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Credit: ICARDA
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In recent years, grasspea has found a new pool of support in the newly independent republics of Central Asia and the Caucasus. For many farmers in the region, forage crops are a new venture. Under Soviet cropping systems, crop rotations were typically grain crops followed by fallow periods, when large areas were completely unsown. But planting forage legumes instead has the potential to give a major boost to productivity. A process of introduction and evaluation of legume crops is already underway, led by crop breeders from the International Center for Agricultural Research in the Dry Areas (ICARDA). In Uzbekistan and Kazakhstan farmers have been impressed by grasspea in particular, with improved lines yielding up to two tons of grain per hectare and having high drought tolerance. Planting the legume has helped farmers to improve the physical condition of their soils, with greater organic matter and nitrogen levels; pests and diseases have also been more easily controlled. The crops have increased the livestock carrying capacity of the land, and reduced the problem of over-grazing on the rangelands. Local breeding teams are currently growing selected lines for seed multiplication and distribution to farmers.
Food and fodder
Among poor farmers in drier parts of Asia and Africa, grasspea is grown for food as well as fodder. However, if people become over-dependent on the crop, for example during times of drought, grasspea has a darker side. Contained within its seeds is a neurotoxin. When consumed in large quantities (over 30 % of a person's diet), for a period of three or four months, the toxin reduces the level of zinc in the brain, leading to a disorder called neurolathyrism. This can cause irreversible paralysis of the legs in adults, and in young children can result in retardation and even death. Grasspea paralysis has been reported since the 17th century, with most outbreaks occurring in times of famine when other crops fail. A well documented case of large-scale crippling occurred in Romania during the Second World War, when labour-camp inmates were fed with grasspea seed for three months. But in the driest months, when grasspea may be the only food available, farming families often have little choice but to accept the health risk, and it is estimated that at least 100,000 people in China, South Asia and Ethiopia currently suffer the debilitating effects of grasspea poisoning.
In response, the ICARDA Lathyrus research team, led by Dr. Ali Abd El-Moneim, has developed new, less poisonous varieties. They began this task by breeding crosses between Middle Eastern varieties of grasspea, which have very low toxin levels, with African and Asian varieties. These crosses were then exposed to a mutation process, in order to increase their genetic diversity, so that lines suitable for a wide range of environments could be developed. The technique, called somaclonal variation, forces the plant cells to mutate and to express genes that were formally dormant. These included genes that controlled the plant's neurotoxin levels. The new cultivars retain around 0.04% neurotoxin, far below the 0.2% thought to be safe for human consumption. They typically yield around 1.5 tons of grain per hectare, given a low rainfall of 200mm per year. Further research is looking at the effects of adding zinc and phosphate to the crops, both to increase yields, and possibly increase human resistance to neurolathyrism through enhanced zinc intake.
