By Joseph Maina
Kenya has made a significant step towards open cultivation of a transgenic cassava variety. This follows the approval of the genetically modified (GM) cassava event 4046 that is resistant to the Cassava Brown Streak Disease (CBSD) by Kenya National Biosafety Authority (NBA) for environmental release.
According to NBA’s Chief Executive Officer, Prof. Dorington Ogoyi, the decision was arrived at following a rigorous and thorough review, considering food, feed, environmental safety, and socio-economic issues.
The disease-resistant cassava was developed under the Virus Resistant Cassava for Africa Plus (VIRCA Plus) project, a collaborative program between KALRO, the National Crops Resources Research Institute of Uganda, and the Donald Danforth Plant Science Center of USA.
The approval paves the way for conducting national performance trials (NPTs) of these varieties before registration and release to farmers. The approval is valid for five (5) years from the date of authorization, NBA clarified.
Trials designed to test new plant varieties for performance compared to varieties currently in the market. Otherwise termed, Value for Cultivation and Use (VCU) trials. The trials are done across the country at specific agro-ecological zones where the full potential of the variety can be expressed.
The tests are done for at least two growing seasons. The designs are usually done with a minimum of two replicates. Data is analyzed each year of testing, with combined data analysis at the 2nd year of testing. NPT report is prepared by KEPHIS after data analysis at the end of each season and National Performance Trials’ committee (NPTC) is convened to discuss the report.
The NPTs are conducted by The Kenya Plant Health Inspectorate Service (KEPHIS). The Service, in consultation with other relevant regulatory bodies, have developed comprehensive guidelines for conducting NPTs for genetically modified organisms, such as the current candidate cassava. After the NPTs have been completed and results analyzed, the NBA is mandated by law to grant the final approval or deregulation of the cassava based on the results of the NPTs.
The improved crop, which has been genetically modified to provide resistance to the destructive CBSD, was developed by the Kenya Agricultural & Livestock Research Organization (KALRO). Cassava now becomes Africa’s fifth biotech crop approved for open cultivation after cotton, maize, soybean and cowpea.
photo credits: CABI
The Biosafety Authority approved the application for environmental release on June 18, 2021.
This followed a comprehensive safety assessment that showed cassava varieties containing event 4046 are unlikely to pose any risk to human, animal or environment health when consumed as food or feed or when cultivated in open fields.
The review process included views sourced from the Kenyan public through a public participation process in conformity with requirement of the Biosafety Act 2009 and the Constitution of Kenya 2010.
“The review process also factored public comments for 30 days, in line with the Kenyan constitution that calls for public participation according to the law” says Dr. Ogoyi.
Currently there are no cassava varieties with natural resistance to CBSD, states the NBA. CBSD is a viral disease spread by whiteflies and by infected cuttings, and it leads to devastating losses of up to 98 percent for cassava farmers in Kenya.
The anticipated increase in cassava yields as a result of the intervention will significantly contribute towards addressing food security and nutrition, as well as manufacturing, which are among the four pillars of the Kenyan government’s “Big 4 Agenda.”
“It is a very important food security crop in Kenya,” said Dr. Simon Gichuki, senior advisor, VIRCA Plus Project. “In some of our counties, it is the staple crop. And when our maize reserves expire, our farmers turn to cassava to fill that gap.
In recent years, CBSD has become an epidemic, and is currently very serious in our coastal region and western Kenya. That’s why we are very concerned because in those two specific areas, cassava is a very important crop.”
Dr. Gichuki notes that cassava yields in East Africa and Kenya in particular are very low compared to those recorded in Asia and South America, a fact that he attributes to disease prevalence of CBSD and its equally lethal counterpart, Cassava Mosaic disease.
“While in Asia and South America they achieve up to 50 tons per hectare, we rarely achieve 10 tons per hectare here in Kenya. The problem is not the farming practices, but things like diseases, in particular CBSD and cassava mosaic virus disease.”
The disease causes corky necrosis in roots that renders them unfit for consumption, and has been responsible for total crop failures in parts of Africa’s Great Lakes region.
“Even plants produced from clean planting material can become infected through the transmission of the virus by B. tabaci whiteflies from infected plants in neighboring plots,” the United Nations Food and Agriculture Organization notes.
“Because the symptoms of CBSD may not be evident on the cassava leaves or stems, farmers may not be aware that their crops are infected until they harvest the roots. The lack of above-ground symptoms makes the use of disease-infected planting material more likely.”
Cassava (Manihot esculenta Crantz) is the world’s most widely grown starch storage root crop and accounts for a third of the total production of staple food crops in sub-Saharan Africa.
Globally, it is grown almost exclusively by low-income, smallholder farmers, and is one of the few staple crops that can be produced efficiently on a small scale without the need for mechanization or purchased inputs.
It produces about 10 times more carbohydrates than most cereals per unit area, and is ideal for production in marginal and drought prone areas, which comprise over 80 percent of Kenya’s land mass.
“The GM cassava application was reviewed by experts on food safety, environmental safety assessment and the relevant regulatory agencies and was shown to be as safe as the conventional cassava variety,” NBA announced in a statement. “Analysis and expert opinions indicate that GM cassava is not expected to change the farming systems currently in Kenya. The effective management of CBSD disease will be of economic and social benefit to the Kenyan population.”
Multi-season analysis of the regulatory field trials showed that the genetic modification resulting in cassava event 4046 did not have unintended effects on plant growth habit, general morphology, reproductive biology, diseases and pest susceptibility.
The approval by the NBA is valid for a period of five years and paves way for conducting National Performance Trials (NPTs), which is the penultimate stage for full environmental release and release to the market. The NBA board will consider full approval after the NPTs have been finalized.
Evaluations of the crop were done over a period of five years in confined field trials in three different KALRO Centers around the country. These included Mtwapa in Kilifi County, Coastal region, Kandara in Murang’a County, Central Region, and Alupe in Busia County, Western Region.
The approved variety has shown high and stable resistance against CBSD, a disease that can result to 100 percent loss of cassava tubers in severe infection, KALRO noted.
