Researchers boost protein content of GM cassava

Cassava's nutrient content could be increased by traditional breeding or GM methods

Flickr/Donald Danforth Plant Science Center

*News editor's note, 20 September 2012: The scientific paper this article was based on was retracted in September 2012. The retraction notice reads: "Following the publication of this article, the authors have been unable to confirm the presence of the zeolin gene within the transgenic cassava plants in several subsequent studies. This raises concerns about the validity of the results reported in the article.

Additionally, the Committee on Research Integrity at Donald Danforth Plant Science Center has carried out an institutional investigation which revealed that significant amounts of data and supporting documentation that were claimed to be produced by the first author could not be found. Given that the validity of the results could not be verified, and in line with the recommendation issued by the corresponding author's institution, the authors retract the article.

The authors apologize to the readers."

[LIMA] The transformation of cassava from a starchy staple lacking in protein to a cheap supply of protein for food, feed and industry, may have come a step closer now that scientists have boosted the crop's protein content.

Cassava is a staple food in many developing countries but has little protein and micronutrients. But although cassava is rich in energy, only 2–3 per cent of its tubers (the edible roots) are made up of protein, giving it one of the lowest protein-to-energy ratios of any staple. Cereals, for example contain 7–14 per cent of protein.

But new research shows that cassava can be genetically modified to contain zeolin protein — increasing its protein levels to 12.5 per cent. The findings were published in PLoS ONE last month (25 January) by a team of US and Puerto Rican scientists.

According to the authors, a two-year-old child that gets half of their energy from cassava could increase their protein intake from 35 per cent of their daily requirement to more than 100 per cent by switching to the GM crop.

"This illustrates that genetic modification of cassava could be a potentially important component of delivering enhanced nutrition to at-risk populations in the tropics," the paper says.

The research is part of ongoing efforts to improve cassava's nutritional quality.

"The goal is to stack several traits such as vitamin A, protein, iron and zinc," Claude Fauquet, lead author and the director of the Donald Danforth Plant Science Center's International Laboratory for Tropical Agricultural Biotechnology, United States, told SciDev.Net. "For now we have stacked vitamin A and protein and it is possible to get yellow roots with 40 parts per million carotene [about 11 times the normal level in cassava roots] and ten per cent dry weight protein," he said, adding that the plants are being assessed in the field.

But Nagib Nassar, a professor emeritus and well-known cassava breeder, said that the crop suffered from the same problem as all GM crops in that it has "a new genetic structure — not natural — that has not passed through natural selection, so we don't know how this genotype adapts to the environment".

He added that the paper had not provided information about the productivity or palatability of the new cassava strain.

Rodomiro Ortiz, an advisor leading international institutes on crop breeding, said transgenic biofortification was just one of many options for improving cassava, and added that wild and indigenous cassava varieties "are an important source of genes" to improve cassava's micronutrient levels.

Both Ortiz and Nassar referred to the success of a variety of cassava root obtained by conventional breeding and released in Brazil, which tastes good and contains more than 50 times the amount of beta carotene than common varieties.

Link to full article in PLoS ONE