The Cassava Source-Sink (CASS) Consortium: Improving Cassava yield by manipulating central carbon pathways
Frank Ludewig1, Alisdair Fernie2, Stefan Gerth3, Andreas Giesel4, Wilhelm Gruissem5, Lukas Mueller6, Ekkehard Neuhaus7, Donald Ort8, Uwe Rascher9, Mark Stitt2, Samuel C. Zeeman5, Uwe Sonnewald1
1FAU, Erlangen, Germany; 2MPI-MPP, Golm, Germany; 3Fh-IIS, Fürth, Germany; 4IITA, Ibadan, Nigeria; 5ETH, Zurich, Switzerland; 6BTI, Ithaca, USA; 7TU, Kaiserslautern, Germany; 8University of Illinois, Champaign, USA; 9FZJ, IBG-2, Jülich, Germany
Cassava is one of the most important food source throughout much of the tropical belt of Sub-Saharan Africa. While productivity is often limited by biotic and abiotic factors, inherent yield capacity is also relatively low compared to other crops in terms of productivity per day; harvest index is also low compared to potato or sweet potato. Over the past 30 years much has been learned about plant metabolic pathways and fluxes, suggesting new avenues of crop improvement that could be exploited to increase productivity in crop plants. There is evidence to suggest that root and tuber crop yields may be restricted by either the ability of the leaves to export photosynthetic products to the roots or by bottlenecks in the ability of storage organs to import and accumulate those products. Following these ideas, transgenic potato plants have been developed with increased tuber yields under greenhouse conditions. Cassava is a root crop with morphological and genetic similarities with potato. In a multigene approach, the CASS consortium aims at simultaneously manipulating source and sink metabolic processes with the goal of creating transgenic Cassava plants with dramatically increased yield. Increasing cassava productivity will be of major benefit for smallholder farmers in Sub-Saharan Africa (SSA). To increase cassava productivity a three-pronged strategy is followed:
To accomplish this, leading experts in plant ecophysiology, molecular biochemistry and physiology, biotechnology and cassava breeding have teamed-up to improve cassava productivity. Besides a systems biological approach, molecular tools are developed allowing the spatial and temporal engineering of cassava source-to-sink relationship to increase starch production. Engineering efforts are complemented by validation and evaluation of transgenic and existing cassava genotypes as well as farmer-preferred varieties with improved productivity and increased storage root starch content for breeders and farmers.