1. Institute of Virology; Slovak Academy of Sciences; Bratislava Slovakia
2. Department of Biological and Biochemical Sciences; Faculty of Chemical Technology, University of Pardubice; Pardubice Czech Republic
3. USDA, Agricultural Research Service, Plant Genetics Research Unit, Department of Biochemistry; University of Missouri; Columbia SC USA
4. Institute of Microbiology; Academy of Sciences of Czech Republic; Prague Czech Republic