KENYA

Gene-editing breakthrough could put root veg on more tables
Cassava may have finally found a permanent place on Africa’s tables, thanks to gene-altering research that aims to delete its ‘not so good’ alter ego.Dr Cecilia Mweu, senior research fellow and current director of the Institute for Biotechnology Research at the Jomo Kenyatta University of Agriculture and Technology (JKUAT) in Juja, Kenya, has made a breakthrough in making cassava safer for human consumption while also ensuring it lasts longer post-harvest.
By using advanced genetic techniques (genome editing), Mweu and her team successfully removed the toxic substances found naturally in cassava that are harmful to humans if not properly processed. Cassava, one of Africa’s favourite traditional meals, is a root vegetable rich in protein.
“Cassava is Kenya’s second-most significant edible root crop after the Irish potato. The main cassava growing areas are western and coastal regions,” Mweu said.
Cassava contains the compound cyanogenic glycoside, which can lead to cyanide poisoning if it is not correctly processed through soaking, drying and scraping before consumption. This negative side to the otherwise delicious meal has earned it a bad reputation over the years, making most people opt for sweet potatoes, arrow roots and maize.
‘Editing’ the poison away
According to Mary Maina, a grocer in Nairobi, most residents in Nairobi tend to shy away from cassava due to what they hear on the news.
“I sell cassava in my stall, but only a handful of customers are willing to buy it. Most of the people will tell you that they have heard of it killing people, while others will say it is bitter and, thus, avoid it,” Maina told University World News.
Mweu’s research may be the solution to the problem. “Cassava leaves and roots, the main plant parts eaten by human beings, contain cyanogenic glycosides. When enzymes break down these compounds, they release cyanide, which is poisonous,” she said. “When this compound is consumed in large quantities, it can lead to rapid breathing, dizziness, even coma and death,” she said.
“Our research works by identifying the region where the gene responsible for producing cyanogen in cassava is, after which the genome editing tool (CRISPR-Cas9), molecular scissors, works by guiding a DNA-cutting enzyme, Cas9 to a specific location in the genome. Once Cas9 is directed to the target, it cuts the DNA (cyanogen gene), allowing for the removal of the harmful cyanogen,” Mweu explained.
Differences difficult to detect
There are two known types of cassava: a bitter one (most poisonous) and a sweet one (least toxic). The bitter cassava contains higher levels of cyanide, and vice versa. Unless tested in a lab, it is almost impossible to visually differentiate between a bitter and sweet cassava, which is one of the primary reasons why some people have fallen victim to it.
However, the table below shows several known differences, according to Mweu:

Luckily for consumers, Mweu’s gene editing will target both types of cassavas. “Although our gene editing was on a specific variety (TMS 60444), it can be applied to both sweet and bitter cassava,” she said.
Tackling malnutrition and food security
Africa produces about half the world’s cassava, making it an essential part of the continent’s food and nutrition security requirement. This breakthrough, therefore, means that cassava will become more marketable and safer for consumption, thus reducing over-reliance on staple foods such as maize in Kenya. This will help relieve malnutrition and food insecurity in Kenya and other cassava-growing regions.
A longer shelf life will also allow farmers to keep their produce in storage for longer, limiting losses.
The International Centre for Genetic Engineering and Biotechnology (ICGEB) has recognised Mweu’s work. The institute lauded Mweu’s research, commending its scientific impact and regional relevance.