Our Purpose

Our primary goal is to create yield improved cassava plants for smallholder farmers that don´t require additional inputs by altering the plants source-sink balance in favor of the storage root. By analyzing existing cassava germplasm and creating new cassava germplasm with alterations in source-sink balance, we increase the biological knowledge for this crop and contribute to the global cassava research community.

Cassava Source-Sink relations

The Cassava Source-Sink project is investigating ways to boost yields of cassava, a hardy and crucial crop for smallholder farmers across Africa, by addressing a biological phenomenon known as “source-sink relations”. This phenomenon describes to which degree different plant varieties produce, distribute, and use assimilates. In the context of cassava this can mean for instance that one cassava variety produces a lot of leaves and stem tissues, but only little edible storage roots, while another cassava variety produces less leaves and stem tissues, but a lot more edible storage roots. Find out how researchers are working to get the balance just right to ensure optimal growth of the edible roots.
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This video was created by Gates Agricultural Innovations with input from the Cassava Source-Sink Project. Gates Agricultural Innovations believes that all lives have equal value and was created to accelerate the most promising agricultural innovations being made available to those who need them most: smallholder farmers in sub-Saharan Africa and South Asia. More information on Gates Agricultural Innovations can be found here.

Our Science

The main goal of the CASS program is to significantly increase cassava yields, focusing on producing high-quality storage roots, even with minimal use of fertilizers and pesticides. One of the key areas we’re focusing on is the relationship between how cassava plants produce and store energy (source-sink). By optimizing this relationship, we can develop new cassava varieties that grow faster, use nutrients more efficiently, and produce more storage roots. These new varieties can then be bred with cassava varieties that are popular with farmers, or we can directly modify the DNA of farmer-preferred varieties to introduce these new traits.

Our plan for creating cassava plants that work well for farmers in Sub-Saharan Africa involves three main strategies to increase the amount of storage roots:

  1. Shorter stems: By reducing the length of the cassava stem, a strategy inspired by the “Green Revolution”, we expect the plants to use fewer nutrients in the aboveground plant parts and in turn produce more storage roots.
  2. Improving nutrient transport: Cassava plants lose photoassimilates, as they travel through the plant. We aim to help the plant reload sugar and nutrients, which will increase storage root growth.
  3. Boosting storage root growth: We plan to directly enhance the growth of storage roots by encouraging more cell divisions for the formation of new starch-storing cells.
  4. Boosting plant metabolism: We plant to boost storage root metabolism by strengthening metabolic pathways involved in the conversion of sugars into starch or the production of energy.

Since plants typically balance its production and consumption processes, individual alterations to production or consumption might only have a moderate effect. However, combining approaches that improve the delivery of assimilates to storage roots with approaches that increase the growth of storage roots and its starch forming capacity, can create a “push-pull” effect (Figure 1) with a more extensive effect on storage root productivity.

Figure1. Illustration of the Push-Pull concept. By combining an increased delivery of photoassimilates to storage roots with an increased storage root growth and starch formation, we expect to be able to significantly improve cassava storage root yield.

While we expect all our alterations in itself to have a positive effect on cassava yield, more extensive positive outcomes will likely be achieved by their combination in the long term.
In summary, the CASS program is working to create cassava plants that grow more efficiently and produce better yields. By enhancing the productivity of cassava, a staple crop for millions in Sub-Saharan Africa, the results of the program will support smallholder farmers who rely on cassava for both food security and income. The improved varieties will help farmers achieve higher yields even under challenging conditions such as poor soil fertility and unpredictable rainfall, which are common across the region.
These innovations will not only increase crop output, but also reduce the need for extensive farming inputs, making cassava cultivation more cost-effective and sustainable for small-scale farmers. The insights we gain could also lead to future improvements in cassava breeding using advanced techniques like genome editing, ensuring long-term resilience and productivity. By empowering smallholder farmers with better-performing cassava plants, the CASS program would contribute to reducing hunger, improving livelihoods, and driving economic growth in rural communities across Sub-Saharan Africa.

About the Project

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