Viruses of cassava

PI: Dr. Stephan Winter

We are monitoring the viruses of cassava Manihot esculenta a world crop of high importance to provide food for many million people in Sub Sahara Africa, South America and Asia and for production of starch, alcohol and other industrial products. On the African continent, cassava mosaic viruses and cassava brown streak viruses are the major constraints to cassava cultivation and production. While the cassava mosaic viruses are present wherever cassava is grown on the continent, the viruses causing brown streak disease are newly emerging viruses that are rampant in particular in East and Central Africa. Their dissemination and spread to West Africa would cause serious impact to cassava production and has to be prevented. 
We study the virus genetic variability and follow adaptation of viruses, the development of new strains or variants and virus population drifts eventually causing more serious diseases. The identification of viruses or pathogenic variants and the biological characterization supports early interventions for disease control and prevention.

Cassava brown streak viruses

PI: Dr. Stephan Winter

The role of cassava brown streak virus proteins for development of disease and vector transmission is studied taking advantage of infectious virus clones developed at the DSMZ laboratories and cassava genotypes showing differential responses following virus infection. Movement, tissue invasion and replication of viruses in single and mixed infections are central themes of our research. 

Virus and vector elements governing circulative and non-circulative transmission of plant viruses 

PI: Dr. Stephan Winter, Dr. Paolo Margaria

We study the role of virus proteins in vector transmission using infectious virus clones of cassava mosaic viruses, cassava brown streak virus and cucumber vein yellowing virus isolates and strains. In earlier studies, we discovered that particular coat protein mutants of begomoviruses can circulate through the insect while transmission is inhibited and localized circular transmission to particular amino acids moieties in the core region of the virus. 
Using a similar approach, we seek to identify proteins of the non-circulative transmitted ipomoviruses to identify genes critical for virus transmission. The cucumber vein yellowing virus is efficiently transmitted by B. tabaci in contrast to cassava brown streak virus that requires high whitefly numbers for efficient virus transmission and infection. Mutational analysis of CVYV genes will allow identification of virus genes critical for transmission to transfer the knowledge onto cassava brown streak virus. Interaction studies with whitefly proteins will then localize virus receptors critical for non-circulative transmission.

Natural resistance in cassava against cassava brown streak viruses

PI: Dr. Stephan Winter

We are conducting a massive screening program to identify cassava genotypes resistant to CBSD. We have selected resistant cassava lines through rigorous inoculation screenings with defined reference viruses. 
All techniques for highly competent virus research are established in the laboratory, from advanced virus infection methods using recombinant virus clones and infections by agrobacterium mediated inoculation to particle bombardment using gold particles as carrier to infect plants by ballistics.

The combination of profound virological knowledge of virus biology combined with the most advanced techniques in virology and innovative ideas bring us into the center of international efforts to search for improved and healthy cassava materials for resistance validation in the natural environment. This work generates fundamental information for genetic improvement of the crop and provides the sources needed to make substantial progress in cassava breeding for CBSD resistance.