Teamwork delivers results in addressing cassava virus diseases!

“If you want to go quickly, go alone, if you want to go far, go together.”
The meaning of this African proverb is well manifested by the Virus Vector Ecology Group (VVEG) team at IITA’s Eastern Africa Hub as James Legg, IITA Plant Health Scientist and team lead, shared on its progress and successes towards addressing the viral disease challenge facing cassava in Africa and even Asia.

The VVEG team is divided into several subteams working on different angles to find innovative solutions to control the spread of the two major virus diseases, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), to improve cassava productivity in Africa and Asia. Legg highlighted some of the notable outcomes of the teams at a virtual seminar titled “Teams, Whiteflies, Viruses, and More​​“, held at IITA Eastern Africa Hub, Dar es Salaam, Tanzania, on 17 September.

The whitefly team

Cassava whitefly, Bemisia tabaci, is the vector that transmits the viruses that cause CMD and CBSD. Efforts to control the diseases start with proper identification of the vector. The Whitefly team is therefore working on developing simpler but sensitive diagnostic tools geared towards identifying the various subgroups of the cassava whitefly and their distribution in the region. One such technology is the use of Kompetitive Allele-Specific PCR (KASP). Using this in-house technology, the team identified and characterized the whitefly population in Eastern and Central Africa and found evidence for hybridization between genotypes of cassava Bemisia tabaci in Eastern Democratic Republic of Congo (DRC).

The team is also working on innovations to effectively control the whitefly pest, including the use of essential botanical oils, soft chemistry pesticides, and entomopathogenic fungi. Legg particularly noted that excellent results have been obtained from the lab trials on the effectiveness of some essential oils such as Patchouli in reducing whitefly populations and also Flupyradifurone, a soft chemistry pesticide developed by Bayer which was found to be significantly more effective than Imidacloprid—the currently most-widely used pesticide. Flupyradifurone also had fewer nontarget effects.

Cassava virus team

The virus team is working on under­s­tan­ding developing diagnostics to detect viruses in cassava plants. This is important as part of efforts to control the disease spread by ensuring clean and disease-free seed. The team has developed a modified Loop Mediated Isothermal Amplification (LAMP) protocol for detecting cassava brown streak viruses. This method can be cheaper, quicker, and more portable than the currently used real-time polymerase chain reaction-based method. The new LAMP technique will be extremely useful to the Tanzania Official Seed Certification Institute (TOSCI) for certification testing that needs to be done in the cassava as well as other seed systems.

The team is also conducting surveillance to monitor the spread of CBSD to new areas. Recent surveys implemented together with national research systems in Tanzania, eastern DRC, and Zambia have revealed that the disease is spreading eastwards and southwards through south-eastern DRC, northern Zambia as well as the western part of Tanzania along the shores of Lake Tanganyika.

Cassava Seed systems team

Previously farmers replanted their old cassava stock or borrowed from neighbors because of a lack of cassava seed systems, contributing to the spread of both CMD and CBSD.

The cassava seed team is working together with TOSCI, TARI, MEDA, and other partners in Tanzania to modernize cassava seed systems. This includes putting in place protocols and systems of quality assurance for disease-free seed. The quality control certification guidelines have been developed and adopted as law in Tanzania, Rwanda, and Burundi to guide production and supply of cassava quality seed. The team has also rolled out the use of SeedTracker, an ICT system facilitating real-time e-certification of clean seed in Tanzania; currently, more than 100 seed producers are registered on the platform.

Nuru team

To tackle the challenge of diagnosing plants affected by the viral diseases, IITA and Pennsylvania State University, USA, have collaborated to launch Nuru (Swahili for light), an artificial intelligence, phone-based disease diagnostic application. It recognizes leaves damaged by CMD and CBSD but also damage by green and red mites.

The team has made many improvements in the performance and accuracy of NuruAI in detecting diseases and pests. In this regard, NuruAI has been found to outperform trained extension officers in diagnosing cassava diseases. NuruAI has been used to monitor cassava diseases in 19 African countries with Tanzania, Kenya, and Ivory Coast as use hotspots.

“Life is what happens to us while we are making other plans,” says another saying. All the outcomes have boosted the team’s morale to take on new challenges. The plans for the next three years (2020/2023) shared by Legg include continuing to control the spread of the cassava viruses through clean seed systems and the development of better, faster, cheaper, and more effective diagnostics. With good collaboration, the team is excited to embark on a new journey of R4D and P4D adventures.

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