Viral diseases of plants cause enormous economic losses through yield reduction, predisposition to biotic and abiotic stresses, impairment in quality, and increase in the production cost due to inevitable management practices. In recent years, the scenario of viral diseases of plants in India has changed considerably. There was an increase in the incidence of viral diseases of plants during the seventies and eighties as a result of introduction of intensive high input cropping systems and introduction of new crops and high yielding varieties. During that period, cucumo- gemini-, poty- and tobamoviruses were the most commonly occurring viruses. In the nineties, ilar- and tospoviruses emerged as major pathogens of a variety of crops, and there was a sudden spurt in the diseases caused by geminiviruses. In addition, state-of-the art diagnostic technologies helped in the identification of the viruses associated with chronic diseases like sterility mosaic disease of pigeonpea, bunchy top of banana and foorkey disease of large cardamom. The problem is compounded by the increase in the emergence of ‘new’ viruses and frequent reemergence of viruses affecting plants. All these pose a challenge for effective diagnosis. Factors leading to the emergence of new virus disease problems and the need for sensitive diagnostic systems for their management would be discussed.
