Plant virus diseases are a major limiting factor to quality and productivity of many cereals, horticultural, ornamentals and other economically important crops around the world. Annual losses due to virus diseases may vary, but under the pathogen favorable conditions, virus diseases may lead to disastrous consequences to farming community. As there is no cure for virus diseases, the management options emphasizes on exclusion of the virus, minimizing virus spread, and development of host plant resistance. The scientific literature concerning virus occurrence, characterization, diagnosis, detection, and management of plant viruses is growing at a fast pace. The book covers recent information on emerging and re-emerging plant viruses affecting important crops in tropics and subtropics. The book provides the comprehensive information on disease distribution, occurrence, properties of the virus including the recent approaches for virus diagnosis, viruses affecting horticultural crops, genetic transformation and induced systemic approach for disease resistance in virus affected plants. Begomo viruses and Illarviruses have been dealt in detail. The coverage of information on various topics is up-to-date and provides thought provoking ideas for addressing important viral disease problems in the tropics and subtropics.