Avijit Roy was born in Kolkata, India, and received his bachelor's degree in agricultural sciences in 1994 from Bidhan Chandra Krishi Viswavidyalaya in West Bengal, India. He received his MS and PhD degrees in plant pathology from the Indian Agricultural Research Institute, New Delhi, in 1997 and 2001, respectively. For his MS research work in plant pathology, Roy was awarded the prestigious Professor M. J. Narasimhan Academic Merit Award by the Indian Phytopathological Society. His PhD dissertation focused on serological and molecular characterization of citrus tristeza virus (CTV) isolates from different citrus-growing regions of India. For his PhD research, he was awarded the Jawaharlal Nehru Award in 2002—one of the highest academic achievements in the field of plant protection awarded by the Indian Council of Agricultural Research. Roy continued his research as a post-doctoral research associate under the supervision of Dr. Ronald H. Brlansky in the Department of Plant Pathology at the Citrus Research and Education Center, University of Florida. During his post-doctoral training from 2001 to 2006, Roy's research focused on citrus viruses and diseases caused by xylem- and phloem-limited fastidious prokaryotes. His research produced several peer-reviewed research articles.
With a strong passion to utilize his research skills and a desire to explore new horizons, Roy began his corporate career in June 2006. He joined Bangalore Genei, the pioneer biotechnology company in India, as a research leader to oversee contract research projects on plant-pathogenic fungi, bacteria, nematodes, and viruses. Although Roy enjoyed the challenging diversity of research in the corporate world, he strongly felt the lack of opportunity to publish his work in scientific journals. He returned to academia, rejoining Dr. Brlansky's laboratory from 2008 to 2014 and then transitioning to the USDA–ARS Foreign Disease and Weed Science Research Unit at Fort Detrick, Maryland, as a research molecular biologist. In 2016, he was appointed to the position of molecular biologist at the USDA–APHIS–PPQ Center for Plant Health Science and Technology (CPHST) Laboratory in Beltsville, Maryland.
Roy has applied methods of molecular biology to characterize viral diseases of citrus, starting with CTV. Tristeza disease has been a principal concern of citrus virologists for 90 years, and complex interactions among the virus, its aphid vectors, and its citrus hosts have been documented. Roy determined and analyzed genomic sequence data from many isolates of CTV obtained from Florida, Puerto Rico, and around the globe. Different genotypes of CTV are known to exist in naturally and graft-inoculated citrus, and Roy showed that single-aphid transmission could be used to separate complex isolates into their single-genotype components and that strains with recombinant genotypes could be isolated in the same way. He also used the extensive collection of strains of CTV maintained by the USDA–ARS at Beltsville to develop a series of five genotype-specific conventional RT-PCR assays for CTV. He further combined these assays into single multiplexed RT-PCR assay that can simultaneously detect CTV infection and identify the genotypes present in a Citrus sp. Tristeza has long been controlled partially by planting on CTV-resistant trifoliate rootstocks, in which the virus was assumed not to propagate. Roy documented the unexpected finding that trifoliate resistance-breaking strains were present in Puerto Rico prior to 1992. He also documented that the brown citrus aphid, Toxoptera citricida, could preferentially acquire and transmit stem-pitting (SP) strains of CTV more frequently from mixed infection of SP and non-SP isolates. All of his research work has provided methods of detection of CTV genotypes and insights into the biology of the host–pathogen–vector system.
Roy has also made significant contributions to research about the citrus leprosis (CiL) disease complex, which is an emerging problem in Central America and Mexico, a current problem in Brazil, and a historical problem in Florida. It is associated with two unrelated taxa of viruses. With the advent of innovative next-generation sequencing (NGS) technology, Roy expanded his research interests and utilized NGS approaches for virus discovery and characterization. He published a series of research papers on the CiL disease complex between 2013 and 2015. He determined the genome sequences of (1) citrus leprosis virus C2 (CiLV-C2), a novel cilevirus causing symptoms similar to those of CiL in Colombia; (2) nuclear citrus leprosis virus (CiLV-N), a citrus strain of orchid fleck virus infecting multiple citrus species in Mexico; and (3) CiLV-N0, an ancient nucleo-rhabdovirus associated with CiL disease recorded in herbarium specimens from Florida. Roy investigated the complex relationships among leprosis viruses, hosts, and mite vectors and reported his findings in 2015 in a Focus Issue of Phytopathology on emerging and re-emerging diseases. In this work, Roy provided evidence that CiLV replicates inside the mite vector. Since CiL is strictly a local lesion disease, with no systemic infections of plants known, the virus is likely an insect virus that uses citrus as a vector, rather than a host. This collaborative multidisciplinary research work has great implications for the control of CiL disease complex.
Roy and his team members utilized NGS approaches for analyzing genomics and RNAi degradation products via NGS to determine the complete genome sequence of an endogenous pararetrovirus associated with citrus blight disease and the viral pathogens of regulatory importance: the first report of CiLV-N from Colombia and the first reports of the hibiscus strain of CiLV-C2 in Hibiscus rosa-sinensis in Florida and in sweet orange in Colombia.
Currently, Roy is focusing his research on development of advanced molecular methods and application of new detection and identification technologies for citrus viruses of regulatory concern. He serves as a virology subject-matter expert for the Plant Protection and Quarantine Molecular Diagnostic Working Group, aimed at expanding the use of molecular diagnostics into the agricultural quarantine inspection environment. In addition, he is a member of the Cilevirus Study Group of the International Committee on Taxonomy of Viruses and of three committees of The American Phytopathological Society: Diagnostics, Emerging Diseases and Pathogens, and Virology.