Virology, a branch of biological science was developed with the discovery of Tobacco mosaic virus in 1898. Viruses are known to infect all sorts of living organism and those known to be restricted within plant kingdom are referred as plant viruses. Although a few groups of plant viruses are known to infect insect vectors, so far none of the plant viruses is known to infect higher animals including human beings. The size of plant viruses ranges between 16 and 2000 nm and generally organized with nucleic acids and protein in either cubic or helical symmetry resulting in isometric or rod shaped architecture. During 1971, another class of infectious phytopathogen containing only nucleic acids and no protein coat, and causing diseases similar to plant viruses was discovered in potato and referred as viroid (Singh 2014). Plant viruses are important constraint in world agriculture. Of all the phytopathogens, studies of plant viruses have received special attention as they are difficult to manage. Numerous plant viruses are presently known globally and almost all the crop species are affected by one or the other viruses. Plant viruses were discovered in late 1880s. Over the last three decades, application of molecular methods revolutionized our understanding of plant viruses. Viruses are of simple biological identity that undergo continuous changes in their genetic makeup and thereby exist in numerous variants. The continuous evolution in viruses poses a great challenge in their identification and classification. No single property of viruses is adequate to identify them.

Dr. K. Subramanya Sastry is currently retired and has last worked as Principal Scientist (ICAR), National Research Centre for Sorghum, Rajendranagar, Hyderabad from 1991 to 1998. His areas of interest are teaching and research in plant Virology, pathology, Microbiology. He has total 27 years of extension experience in Indian council of Agricultural Research and 5 years of teaching experience in Department of Botany, S.V. University, Tirupati. He has published total of 5 books and 83 research papers. Published three books on plant virology from Springer during 2012-14. Dr. Bikash Mandal is currently working as Principal Scientist in Advanced Center for Plant Virology, Indian Agricultural Research Institute (IARI), New Delhi. His research and teaching area is Plant Virology. He has total 153 publications that includes 2 books, 8 book chapters, 72 research papers, 5 popular technical articles, 65 conference abstracts. He is the editor-in-Chief of Journal 'VirusDisease' (Springer) and VirusResearch news (Newsletter). Dr. John Hammond is currently working as Research Plant Pathologist, United States Department of Agriculture, Agricultural Research Service, Floral and Nursery Plants Research Unit, Beltsville. His major areas of research are viruses affecting ornamental crops, with emphasis on potyvirus, potexvirus and carlavirus detection, differentiation, and methods of introducing resistance, use of transgenic plants to examine virus resistance and infectious viral clones to determine factors affecting host range, symptom induction, and systemic movement, and development of microarrays for plant virus detection and identification. Dr. Simon W. Scott has recently retired from Clemson University as a Professor Emeritus in Plant Pathology. His major areas of research were viruses and virus-like agents affecting woody deciduous species with an emphasis on those viruses that affect the dominant fruit crop in South Carolina (peaches). He has established a program to index large blocks of peach trees in the southeastern USA prior to propagation as part of the USDA/APHIS National Clean Plant Network. In addition he has produced extensive sequence data for a number of Ilarviruses allowing long-standing taxonomic anomalies to be corrected. Dr. Robert William Briddon has worked as Principle Investigator in Agricultural Biotechnology Division, National Institute of Biotechnology and Genetic Engineering (funded by United States Department of Agriculture (USDA) through the International Centre for Agricultural Research in the Dry Areas (ICARDA, Islamabad Office). His research area is in study of vector transmission of plant infecting viruses. Particularly the interactions involved between virus and insect vector of circulatively and propagatively transmitted viruses and the evolution thereof. He has total 135 publications in ISI Web of knowledge. He is also a member of British Society for Plant Pathology, European Whitefly Study Network and International Committee on Taxonomy of Viruses.