My Journey Towards Development of Disease Resistant Cassava
As a young boy, I grew up knowing cassava was an important food crop, especially in times of hunger. My grandmother used to narrate how the crop was once the only food available during the ‘cassava hunger’. But there was little cassava production in my region, and the only root and tuber crops being grown were Irish and sweetpotatoes, arrow roots and a little bit of yams. Maize was slowly becoming the main staple food crop and coffee was the cash crop. Most of these food crops were seasonal, and we changed from one diet to the other as the seasons changed.
It was not until later years as an agriculture student that I came to appreciate the value of cassava as a food security and industrial crop, mainly because of its resilience under unfavorable growing conditions. I fully understood the stories from my grandmother. Little did I know I was to spend my early years as a scientist working to solve one of the major disease problems of the crop. What seemed like a dream is slowly coming to reality.
My first major assignment as a young scientist at the Kenya Agricultural and Livestock Research Organization (KALRO, then KARI) was to join a team of scientists in solving an emerging threat to cassava production in the region, the cassava brown streak disease (CBSD) using modern biotechnology. Why CBSD and why modern biotechnology? Because to date, none of the cultivated cassava varieties are resistant to CBSD and the best CBSD tolerant cassava plants currently available to farmers may still show some virus damage, and may thereby cause the disease to spread further. The use of modern biotechnology was therefore one of the best options to incorporate CBSD resistance into cassava cultivars carrying farmer-preferred characteristics.
I could not imagine it would take us close to 10 years of hard work, dedication and commitment to come up with an additional solution (and maybe the only current solution) to the CBSD problem. It has been a journey of learning, interactions and sacrifices, from trainings in different molecular biology sciences, to biosafety regulations, science communications, spending hours in the laboratories and fields, traveling across the country, the region and the world over.
Finally, there is light at the end of the tunnel, and KALRO has submitted an application to the National Biosafety Authority (NBA) for environmental release and placing on the Kenyan market of a cassava that is resistant to cassava brown streak disease (CBSD), developed using modern biotechnology. The disease resistant cassava was developed under international collaboration between KALRO, the National Crops Resources Research Institute (NaCRRI) of Uganda, and the Donald Danforth Plant Science Center (DDPSC). The researchers introduced a small part of two viruses that cause CBSD into the cassava plant to make it resistant. The process used augments a naturally occurring plant defense mechanism against viruses.
The improved cassava was first evaluated in the greenhouse. The best performing line was then evaluated in confined field trials (CFTs) in five different locations in Kenya and Uganda over a period of five years, and showed high and stable defense against CBSD. Upon approval, the cassava will get into cassava breeding programs and the new improved varieties will get to farmers through normal government variety release processes.
Studies on roots and leaves of the improved cassava indicated that there were no changes in the growth characteristics, dry matter content, composition and nutritive value. Analysis across four seasons also confirmed that stability of resistance is likely to remain highly effective over multiple cropping cycles of vegetative propagation since cassava is propagated exclusively by stem cuttings (stakes). The improved cassava does not confer competitive advantage that would make it more weedy or invasive in the environment, and disease resistance does not affect other pests, hence there are no target and non-target pest species, and therefore no impact on biodiversity.
The disease resistant cassava was developed as a public good. In the process of its development, various key stakeholders such as farmers, youth, policy/decision makers and value-chain actors were sensitized through appropriate awareness platforms and field visits to experimental sites. The cassava will therefore not be patented in Kenya or elsewhere. This means that there will be no charge or restriction of rights by any of the institutions that was involved in its development. The cassava will be available to breeders to develop it further into new cassava varieties suitable for different cassava growing regions of Kenya.
Cultivation of the disease resistant cassava will follow same practices as for conventional cassava and can be grown in all cassava-growing regions in the country. Stakes (cuttings) for planting will cost the same as for other cassava varieties while production, multiplication and distribution of planting materials will be done using the normal system of releasing new cassava varieties by KALRO and other stakeholders. Once disease resistant farmer-preferred cassava varieties are made available to farmers, this will improve the quality and increase the quantity of cassava. This will benefit all the players in the cassava value chain.
This is among the first applications for release of a local product that has been developed by regional scientists using modern biotechnology, to directly benefit our communities. We look forward to seeing more use of modern science in solving our local problems. Kenyan nationals are invited to submit their comments on this application to the NBA. You can contribute towards this public participation process here.
Prof. Douglas Miano is an Associate Professor at the University of Nairobi and Principal Investigator of the VIRCA Plus project in Kenya. You can reach him on dwatuku@yahoo.com
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