Role of quarantine in ensuring biosecurity against transboundary plant viruses

International trade and exchange of germplasm play an important role in the long-distance dissemination of destructive pests including viruses/strains, which may pose potential risk to the agriculture of the importing country. Viruses are one of the most important yield-reducing factors in various crops. The National Plant Protection Services assume responsibility for protecting their respective country from the unwanted entry of new viruses and for coordinating programmes to eradicate those that have recently arrived and are still sufficiently confined for their elimination to be realistic. The exclusion can be achieved by a combination of regulatory and technical approaches that can ensure biosecurity for a country/region. In India, the Directorate of Plant Protection, Quarantine and Storage under the Ministry of Agriculture and Farmers Welfare is responsible for enforcing quarantine regulations and for quarantine inspection and disinfestation of agricultural commodities meant for commercial purpose. The imported germplasm materials including transgenics are subject to quarantine processing at the ICAR-National Bureau of Plant Genetic Resources, New Delhi. The Agricultural Biosecurity Bill has been drafted and is under the consideration of the Government of India. The strategies for biosecurity for plant viruses include stringent quarantine measures for the imported material, domestic quarantine and use of certified disease-free seed and other planting material within the country. The challenges in virus detection include availability of antisera, viral genome sequences in Genebank, detecting an unknown/exotic virus, etc. Attention is now given to issues like developing an antisera bank for exotic viruses, database on sequences of virus-specific primers, Multiplex RT-PCR, Real-time RT-PCR, Loop mediated isothermal amplification, Helicase dependent amplification, etc. Adopting a workable strategy such as post-entry quarantine (PEQ) growing in PEQ greenhouses/containment facility, electron microscopy, ELISA and RT-PCR, 45 viruses have so far been intercepted, which include 19 viruses not yet reported from India viz. Barley stripe mosaic virus, Bean mild mosaic virus, Bean pod mottle virus, Broad bean mottle virus, Broad bean stain virus, Broad bean true mosaic virus, Cherry leaf roll virus, Cowpea mottle virus, Cowpea severe mosaic virus, Dioscorea latent virus, Garlic virus C, High plains virus, Maize chlorotic mottle virus, Pea enation mosaic virus, Peanut stunt virus, Pepino mosaic virus, Raspberry ringspot virus, Tomato ringspot virus and Wheat streak mosaic virus. Besides, 21 viruses not known to occur on particular host(s) in India were intercepted. The infected plants were incinerated and harvest from virus-free plants was released for crop improvement programmes. The risk of introduction of 45 viruses or their strains into India was thus eliminated. Adopting the appropriate technique and the right strategy for virus detection would go a long way in ensuring the biosecurity of Indian agriculture from trans-boundary introduction of plant viruses.