Genetic engineering solves major toxin problem in peanuts

By Joan Conrow

November 2, 2017

Dr. Pooja Bhatnagar-Mathur in her ICRISAT lab in Hyderabad. Photo by Rakesh Nagar

In a major breakthrough for food safety, scientists have used genetic engineering to suppress a fungus that causes aflatoxin, a poisonous carcinogen that can contaminate peanuts, also known as groundnuts.

The public sector research is expected to have significant health benefits for people in Africa and Asia who consume large quantities of peanuts (groundnuts) as a protein source. Livestock can also be harmed by the molds, which may infect groundnuts, maize (corn), cottonseed, chilies and many vegetable crops. Aflatoxin also results in a tremendous amount of food waste because contaminated crops are often destroyed.

Aflatoxin is a very important health concern, Dr. Pooja Bhatnagar-Mathur, senior scientist at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad, India, told the Alliance for Science.

What’s happening is that the fungus, Aspergillus flavus, produces this aflatoxin, which bioaccumulates in the body, and it just stays in that food chain, she said. Studies have shown aflatoxin also being traced back to human milk, meat and other agricultural commodities. These toxins just keep on bioaccumulating, and chronic exposure can result in predisposition to compromised immune systems, as well as major diseases like cancer and liver cirrhosis.

The problem is compounded for people in developing countries in Asia and Africa, where crops rejected for export to Western nations due to high levels of afllatoxin are recycled back into the domestic market due to lack of control or food testing facilities. And that’s where the local population is exposed to much, much higher levels of this particular toxin, Bhatnagar-Mathur explained.

Scientists were challenged in finding a solution because aflatoxin is a complex problem, involving an interaction of fungus and drought. The fungal spores can remain in the soil for years, infecting plants when they are stressed by heat or drought. Grains also can become infected when stored in the hot, humid, poorly-ventilated conditions characteristic of tropical regions.

It is very difficult to otherwise address this issue of aflatoxin using a conventional breeding approach, and that’s why transgenics or genetically engineered crops come in handy, where we are utilizing genes which would reduce the fungal growth as well as reduce the aflatoxin contamination in these commodities, Bhatnagar-Mathur said.

Public sector scientists at ICRISAT, the Donald Danforth Plant Science Center in Missouri, Lousiana State University (LSU) and the US Department of Agriculture (USDA) collaborated in the research, publishing their findings this week in the Plant Biotechnology Journal.

The team from ICRISAT and Danforth identified and developed small proteins called defensins from alfalfa and the Mediterranean clover. These were introduced into the DNA of an Aspergillus-susceptible peanut variety widely grown in Africa and India, which allowed the peanut to stop the fungus from infecting the plant, according to a press release from the Danforth Center. Another collaboration involving ICRISAT scientists and researchers from USDA and LSU resulted in transferring small RNA molecules from the Aspergillus fungus that are involved in the aflatoxin synthetic pathway. The nuts produced these RNA molecules during fungal attacks and inactivated target genes responsible for aflatoxin synthesis. This technology is also translatable to other crops such as maize, cotton, pistachios, sunflower and almonds.

However, before the breakthrough can benefit consumers, researchers still must conduct field trials in India as well as African countries, to continue developing an aflatoxin resistant peanut. This would mean seeking approvals from the Indian government, which has not yet approved the cultivation of any genetically engineered food crop due to pressure from anti-GMO activists.