defective coat protein he isolated a rare mutant, which had no coat protein but only the free nucleic acid (RNA). (Ref. 1981). The presence of this free RNA prevented the spread of other related TMV mutants, offering an early experimental proof of the phenomenon, later known as "Gene Silencing". Cellwall-free protoplasts of plant cells (mainly of tobacco and Chinese cabbage) were infected with viruses or with their RNA with a high efficiency and used for physiological investigations. Synergism between potato virus x and potato virus y was studied in vivo by classical methods as well as by ultrastructural, i.e. electronmicroscopic techniques. Membership of scientific societies Indian Science Congress Association, life member Indian Phytopathological Society, life member Indian Virological Society, fellow Deutsche Phytomedizinische Gesellschaft Deutsche Virologische Gesellschaft Publications Scientific papers Dutt, M., Sarkar, S. & Dutta, C.T.: Physiological studies on diploid and polyploid varieties of banana. Science and Culture 16, 215,1950 Sarkar, S.: Versuche zur Physiologie der Vernalisation. Biol. Zentralblatt 77, 1–49,1958 Sarkar, S.: Interaction and mixed aggregation of proteins from tobacco mosaic virus strains. Zeitschr. Naturforschung. 15b,778–786, 1960 (See also Caspar, D.L.D.: Assembly and stability of the tobacco mosaic virus particle. Adv. in Protein Chemistry 18, 37–121, 1963) Sarkar, S.: Relative infectivity of tobacco mosaic virus and its nucleic acid. Virology 20,185–193,1963 Sarkar, S.: Assay of infectivity of nucleic acids. In METHODS IN VIROLOGY (Maramorosch and Koprowski eds.) Vol. 2, 607–644, Academic Press, New York, 1967 Sarkar, S. & Schilde-Rentschler, L.: Interaction of TMV proteins during electrophoretic separation in polyacrylamide gels. Molec. Gen. Genetics 103, 244–247, 1968 Sarkar, S.: Use of protoplasts for plant virus studies. In METHODS IN VIROLOGY (Maramorosch and Koprowski eds.) Vol.6, 435–456, Academic Press, New York, 1977 Matthews, R.E.F. & Sarkar, S.: A light-induced structural change in chloroplasts of Chinese cabbage cells infected with turnip yellow mosaic virus. Jour. Gen. Virol. 33, 435–446, 1976 Sarkar, S.& Smitamana, P.: A truly coat-protein-free mutant of tobacco mosaic virus. Naturwissenschaften 68, 145–147, 1981 Sarkar, S. & Smitamana, P.: A proteinless mutant of tobacco mosaic virus: Evidence against the role of a viral coat protein for interference. Molec. Gen. Genetics 184, 158–159, 1981 Blessing, J. & Sarkar, S.: Isolierung und morphologische Charakterisierung des Kartoffelblattrollvirus (PLRV). Zeirschr. Naturforschung 36c,884–887, 1981 Mayee, C.D. & Sarkar, S.: The ultrastructure of Nicotiana tabacum cells infected with potato virus X and potato virus Y. Jour. Ultrastructure Res. 81, 124–131, 1982 Sarkar, S.: A simple cage