Toxin-free groundnut: ICRISAT finds answer

Scientists at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, have evolved a novel method to eliminate the toxin from groundnuts. The study, published in the October 2017 edition of the Plant Biotechnology Journal, highlights two different genetic engineering techniques employed to reduce toxin levels in groundnuts.

Peanuts or groundnuts are a popular protein-rich snack which people pop into their mouths whenever and wherever possible. However, these peanuts could sometimes be infected with a fungus called Aspergillus flavus, which may contain a dangerous toxin -aflatoxin - which can cause liver damage and cancer. Roasting the groundnuts will not completely destroy the toxin.

The first technique aims to prevent the A.flavus infection on groundnut plants. This was done through the transfer of two resistance genes from the fodder plant Alfalafa to groundnut by genetic engineering approaches. These genes code for molecules called defensins, which greatly improve the immunity of the groundnut plant and reduce the chances of fungal infection.

The second strategy is to prevent the production of aflatoxin in the plant even when it is infected with the fungus. This was achieved through gene-silencing, wherein two small RNA molecules were used to prevent the formation of aflatoxin by suppressing key steps in the biosynthetic pathway of its production.

The ICRISAT scientists successfully demonstrated the results of the above techniques separately in different groundnut plants. The task ahead is to combine the two characters into a single variety through plant-breeding, conduct bio-safety trials and develop regionally adapted groundnut varieties. The apex authority that sanctions such studies in India is the Genetic Engineering Appraisal Committee (GEAC). Dr Pooja Bhatnagar Mathur, who led the ICRISAT research team, hopes to come up with an aflatoxin-free groundnut variety in a few years.

Aspergillus is a soil-dwelling fungus. Two species of Aspergillus, namely A. flavus and A. parasiticus primarily cause production of the toxin. The burden of aflatoxin poisoning is reported to be high in African and South Asian soils. This is a matter of concern in products like peanut butter and other processed foods sold in markets of developing countries. In these countries, the norms of food safety are not strictly followed.

In 2004, Kenya experienced a severe case of aflatoxin poisoning when 125 people died of the disease and several hundred suffered from liver damage. This was a case of acute aflatoxicosis, a disease of liver failure associated with consumption of extremely high levels of aflatoxin in a very short period of time. Since then, the World Health Organisation (WHO) and several research bodies across the world have been focussing on how to reduce the aflatoxin content in crops like groundnut and maize.

Apart from the acute disease the toxin caused in Kenya, there are millions of cases of lower chronic levels of aflatoxin intake by consumption of maize and groundnut, which can lead to liver cancer. WHO reports six lakh new cases of liver cancer annually and over 80% of the deaths by this cancer occur in Asia and Africa.

In addition to liver cancer, aflatoxin has also been linked to immune system disorders and stunted growth in children. Animals and birds also fall prey to this toxin when they are fed with mouldy peanuts and maize. The damage done by this toxin includes hepatitis and enteritis. It's a serious health problem in poultry, cattle and horse farms, too.

Poor post-harvest storage conditions can increase the content of toxin in the seeds. The main predisposing conditions include poor storage conditions; viz., excessive heat and moisture, pest damage and long storage over months in warehouses. In most developing countries, this is the typical scenario.

The permitted level of aflatoxin as per Indian and US standards is 20 ppb (parts per billion). The European standard is even more stringent at 4 ppb. In some infected groundnut products, the level of aflatoxin could be in the range of thousands of ppb.

If these toxic groundnuts are consumed on a regular basis, it will have a cumulative effect and may lead to liver cancer. The results of the genetic manipulations followed by the ICRISAT scientists yielded a level of aflatoxin as low as 1 ppb. This is in contrast to 3,000 ppb of aflatoxin in the control groundnut specimen. Thus, the research indeed could successfully reduce the toxin level within the threshold of Indian, US and European standards.

Therefore, the novel approach that the ICRISAT research team adopted to combat this toxin is commendable. It would be sound strategy if the scientists could successfully fuse the two approaches into a single variety of groundnut. More importantly, it would ensure that groundnut with its high protein content, remains an excellent source of nutrition for a huge population across developing geographies of Asia and Africa without the accompanying health hazard of liver disease.

(The writer is an Associate Professor with the Department of Life Sciences at Christ University, Bengaluru)

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