Characterization of the Immune Response of Cassava Against the Ipomoviruses CBSV and UCBSV (CaVir)

• Applicant: Dr. Samar Sheat
• Subject Area: Plant Breeding and Plant Pathology ; Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566525150

A severe virus disease of cassava caused by two distinct ipomo-viruses (fam. Potyviridae), the cassava brown streak virus (CBSV) and the Ugandan cassava brown streak virus (UCBSV) threatens cassava cultivation in Africa and the livelihood of millions of people. The viruses systemically invade all plant tissues and cause striking symptoms on leaves, stems and roots. When root tubers are developing, large areas of the tubers become necrotized and consequently, the tubers cannot be consumed. This is the main impact of the virus diseases. Cassava brown streak disease (CBSD) has become a significant threat to cassava regions in sub-Saharan Africa and globally, particularly due to the lack of virus-resistant cassava varieties and precise virus screening methods. In the Plant Virus Department of DSMZ, we have developed a robust phenotyping workflow and identified South American genotypes that exhibit broad immunity to all CBSD viruses. The goal of this research project is to characterize the immune response of cassava to U/CBSV. Building on my previous work, I am using genetic, molecular, and biological experiments to uncover the fundamental mechanisms of cassava resistance to U/CBSV. Through innovative methods, we are analyzing virus replication complexes (VRCs) and the interaction of host proteins with critical virus proteins to identify plant interaction partners (key genes) involved in virus replication and spread in plants. Insights and identified interaction partners obtained from the model plant Nicotiana benthamiana are transferred to cassava to analyze and functionally classify orthologous genes in resistant and susceptible lines. Our aim is to compare functional and dysfunctional (loss-of-function) conditions in resistant and susceptible cassava lines to understand virus replication in cassava and contribute to a mechanistic explanation of the immune responses of resistant cassava lines. These insights will be used to formulate new approaches for developing virus resistance, not only for cassava but also for virus diseases of other crops. We expect that the fundamental insights from virus studies with novel Ipomoviruses in cassava will have practical applications in breeding virus-resistant cassava varieties, significantly improving food security and economic stability in affected regions.

• DFG Programme: Research Grants