Researchers join forces tackling cassava diseases in Tanzania

08Oct 2020
Crispin Gerald
Dar es Salaam
The Guardian
Researchers join forces tackling cassava diseases in Tanzania

THE International Institute for Tropical Agriculture (IITA) in collaboration with the Pennsylvania State University based in the United States of America USA, have launched Nuru (Swahili for Light), an artificial intelligence (AI), phone-based disease diagnostic application to tackle the.....

A phone-based disease diagnostic application technology (NuruAI) developed to tackle the challenge of diagnosing the plants being affected by viral diseases.

challenge of diagnosing the plants being affected by viral diseases.

The technology recognises leaves damaged by the disease known as cassava mosaic disease (CMD), the cassava brown streak disease (CBSD) and by green and red mites.

The cassava part of this app was developed here in Tanzania to control the cassava diseases, and since Tanzania is a country where cassava diseases are very important, it has been a focus country for efforts to popularize Nuru.

This has been done through working with farmers and extension staff in Mkuranga District, as well as training farmers, extensions and seed inspection officers in different parts of the country, as well as through demonstrations of the technology at NaneNane exhibitions.

The team has made many improvements in the performance and accuracy of NuruAI in detecting the 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 hotspots.
An important feature of Nuru is that its advice section provides a link to the SeedTracker application through which farmers can identify the nearest source of healthy planting material of improved cassava varieties.

There are currently more than 400 cassava seed entrepreneurs in Tanzania who are part of this network, and this number is set to increase to more than 1,000 in the next few years.

Planting resistant varieties is the best way to control diseases of cassava, and Nuru and SeedTracker working together provide Tanzanian farmers with the tools to identify the diseases and access the resistant varieties to control them.

The efforts of the virus team are being complemented by the cassava breeding team that has been developing new, improved cassava varieties that are resistant to the viral diseases and are high-yielding and retain the traits treasured by their users such as taste, texture, and color.

In addition, the agronomy team is developing the best recommendations for growing cassava. These include identifying the best planting dates, fertilizer combination, and which crops to best intercrop.

With all these efforts in place, the cassava farming community is assured of flattening the cassava virus curve.

Researchers at the International Institute of Tropical Agriculture (IITA) and their partners have been working on many angles to find innovative solutions to sustainably control the spread of the two major virus diseases, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), to save the crop and the food and income of millions of farmers in Africa and even in Asia.

Leading the efforts is James Legg, plant virologist at IITA- Tanzania, who recently shared the progress and successes of these efforts in a virtual seminar titled "Teams, Whiteflies, Viruses, and More” held at IITA Eastern Africa Hub, Dar es Salaam, Tanzania.

The diseases

Cassava Brown streak Disease (CBSD) and Cassava Mosaic Disease (CMD) pose an enormous threat to the food security of 135 million people in Central and East Africa. Nearly all the varieties grown by the farmers are susceptible to the diseases.

Tackling the whitefly

Efforts to control any diseases start with a proper understanding of how the diseases are transmitted.

The cassava whitefly, Bemisia tabaci, is the vector that transmits the viruses that cause CMD and CBSD.

The Whitefly team is therefore working on developing simpler but sensitive diagnostic tools geared towards identifying the various sub-groups 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 has been identifying and characterizing the whitefly populations in Eastern and Central Africa and has found evidence for hybridization between genotypes of cassava Bemisia tabaci in eastern Democratic Republic of Congo.

The team is also working on innovations to effectively control the whitefly pest, including essential botanical oils, soft chemistry pesticides, and entomopathogenic fungi.

Legg particularly noted that very good results had been obtained from the lab trials on the effectiveness of some essential oils such as Patchouli in reducing whitefly populations and Flupyradifurone, a soft chemistry pesticide developed by Bayer that was found to be significantly more effective than Imidacloprid-currently, the most-widely used pesticide. Flupyradifurone also had fewer non-target effects.

Tackling the virus

The virus team is working on 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 is cheaper, quicker, and more portable than the currently used real-time polymerase chain reaction-based method.

The team hopes to transfer the new LAMP technique to the Tanzania Official Seed Certification Institute (TOSCI), for whom it will be extremely useful for necessary certification testing 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 Democratic Republic of Congo (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

Previously farmers replanted their old cassava stock or borrowed from neighbours 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 Tanzania Official Seed Certification Institute (TOSCI), Tanzania Agricultural Research Institute (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.

The two biggest challenges with the application of Nuru in Tanzania are raising awareness of the availability of the technology, which is entirely free, and the current limited number of farmers who have access to smartphones.

IITA is working hard with partners to increase training and awareness raising about the app, and is also linking up with mobile phone companies to convert some of the features provided through Nuru into a format that can be accessed even with regular basic feature phones.

Our aim is to put knowledge on improved cassava farming into the hands of every farmer in Tanzania.

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