We aim to develop robust and yield-improved cassava varieties that will be provided to African smallholder farmers in order to improve food security in Sub-Saharan Africa.
According to the Food and Agriculture Organization of the United Nations, approx. 220 million people suffer from chronic hunger in Sub-Saharan Africa. The tuberous roots of cassava (Manihot esculenta) represent the main source of carbohydrates, making this tropical bushy shrub essential for food security of the African continent.
Cassava is almost exclusively grown by smallholder farmers, who own less than two acers of farmland and have very limited access to the tools of modern agriculture, like heavy farming machinery, pest control or fertilizer. Yield increases therefore have to come from plants that are inherently more productive, even under conditions of low-input agriculture.
Carbohydrates are produced via photosynthesis during the day in the green parts of the plant (Source) and are allocated to carbohydrate demanding tissues in order to sustain metabolism or storage (Sink). Plant source-sink relations are a major determinant of plant yield, as they determine how much resources are diverted to the edible plant part, e.g. cereal grains, maize cobs or underground storage organs like potatoes or cassava roots. In other crop plants, such as wheat or rice, grain yield has substantially been increased over the last decades. This has mainly been achieved by shifting biomass from shoots to grains, thereby increasing harvest index. Hobby farmers know this phenomenon very well from growing tomatoes. Failure to remove emerging side shoots regularly, will result in less and smaller berries because the plant will invest more energy into new leaf growth instead of creating and filling tomatoes.
The physiological basis for increased yield and improved biomass allocation can be attributed to improved photosynthetic carbon assimilation in leaves, long-distance transport of assimilates and their utilization in sink tissues. We aim to develop cassava plants with favorable source-sink relations through genetic engineering of photosynthesis, C/N metabolism, phloem transport, cambial activity and sink metabolism, thereby improving the root yield of cassava.
The Cassava Source-Sink (CASS) project brings together computer scientists, plant scientists and breeders, to combine progress in each field with the common goal to improve plant productivity and to secure future food supply for a growing world population. So far, cassava has not significantly benefited from major advances in modern plant biochemistry and physiology. A better understanding of cassava physiology and biochemistry, however, will be essential to achieve sustainable increases in cassava yield and will be critical for ensuring sufficient food supply in Sub-Saharan Africa (SSA).