The research context 

Throughout Southeast Asia (SEA), cassava (Manihot esculenta Crantz) has become an important upland crop in terms of both rural livelihoods and economic development. It is estimated that over 2 million households in mainland Southeast Asia (MSEA) are engaged in cassava production. Cassava production in the majority of MSEA is a commercially oriented activity, with the crop cultivated to meet the rapidly growing regional and global demand for animal feed, starch-based products, ethanol and biofuel. Cassava products (starch and dried chips) are used in many applications, including the production of sweeteners (glucose, sorbitol) MSG, paper, textiles, pharmaceuticals, processed foods, dairy products, ethanol, animal feed, and pet food, to name but a few. Beyond the domestic utilisation, the export of fresh cassava roots, starch and chips amounts to between $3.5-4 billion USD per year for the region (UN-Comtrade). In response to this strong market demand, cassava production has increased in the region with rapid expansion in Cambodia, Lao PDR, and Myanmar. This has involved significant cross-border trade in planting material (cassava planting stems -referred to as ‘seed’ for the purposes of this proposal) and raw materials (fresh roots and dry chips) with Vietnam and Thailand. There are strong inter-dependencies between countries for both feedstock and processing capacity, access to export infrastructure, access to new technologies, and foreign investment capital.

The problem 

The recent cassava boom has coincided with the emergence and spread of two serious diseases throughout the region. Reported in Thailand in the 1990s, Cassava Witches Broom Disease (CWBD) is now widely distributed in SE Asia, with increasing field level incidence and yield impact. CWBD can cause yield reductions of up to 90%, and affect starch content and quality, thereby affecting root prices due to declining processing efficiency. The second (and most recent arrival) is a member of the cassava mosaic virus family of geminiviruses, which has caused a widespread epidemic with considerable yield losses in Africa. Sri Lanka Cassava Mosaic Virus (SLCMV) was first reported in in Cambodia in 2015, and is now present throughout the major producing regions of Cambodia, and southern and central Vietnam, and symptoms reported Northeast Thailand.

Both CWBD and SLCMV are spread through the movement of infected stems, with secondary infection via invertebrate vectors. Knowledge of the population and dynamics of the invertebrate vectors is very limited in the SEA context, especially in the case of CWBD, where the identity of the disease vectors remain unconfirmed and the disease itself is poorly characterised.

In regards to CMD, farmers’ estimates of yield decline in the initial year of infection is between 30-50% from secondary infection, with experiences from Africa and India indicating that yield losses will increase over time with the replanting of infected stakes. The strong interconnection between the regional cassava economies has resulted in the rapid spread of these diseases across national borders, with significant impacts on household livelihoods and the competitiveness of the cassava sector in the global carbohydrate market.

This project directly addresses these two emergent diseases, which if left unchecked will continue to spread throughout the region devastating cassava production, the incomes of millions of smallholder farmers, and a multibillion-dollar industry. The project consists of a multi-pronged strategy involving breeding, surveillance, agronomy, and seed systems interventions, coupled with engagement with government institutions and agribusiness.

Summary of Objective

Objective 1: Assess the opportunities, challenges and risks for the development of sustainable regional solutions for cassava disease management in mainland SEA including coordinated policy development, sustainable business and public-private funding models;

Objective 2: Enhance the capacity and collaboration between breeding programs in mainland Southeast Asia to develop new product profiles for commercially viable cassava varieties by identifying and incorporating known and novel sources of resistance to Cassava Mosaic Disease (CMD) and Cassava Witches Broom Disease (CWBD) into national breeding programs:

Objective 3: Develop, test and deploy diagnostic protocols, tools, and information platforms fit for purpose in monitoring, surveillance, and certification applications; and

Objective 4: Develop and evaluate technically feasible and economically sustainable cassava seed system models for the rapid dissemination of new varieties and clean planting material to smallholder farmers in different production systems and value chains.

The project will develop technically viable and economically sustainable solutions to address the disease related problems, test and evaluate methods for scaling, and prepare the region to defend against future pest and disease incursions by strengthening capacity and networks, and investigate opportunities for public-private funding models.

Outputs of the project will include:

1. Commercially competitive and acceptable cassava varieties resistant to CMD and yield high the existing varieties under disease pressure through a process of screening, breeding and selection;
2. Source of resistance to CWBD identified and introduced into cassava breeding programs;
3. Enhanced regional diagnostic protocols, tools and information platforms fit for purpose in monitoring, surveillance, and certification applications across scales;
4. Models for the development of economically sustainable cassava seed systems for the rapid dissemination of new varieties and clean planting material to farmers in different value chains.
5. Business models, policy recommendations and alternative funding models for sustainability of interventions across multiple scales.

The overall aim of the project is to

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Let’s build something together.

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