Significant plant virus diseases in India and a glimpse of modern disease management technology

Abstract

India has a diverse agroclimate representing tropical, subtropical and temperate climates with zones ranging from average to high in temperature, humidity and rainfall; from low to scarce rainfall in deserts to cold to very cold plains and upland areas. Thus it is the home of one of the richest flora and fauna in the world. For pests and pathogens, too, tropical and subtropical climates are ideal for growth and development. A majority of the world’s fruits, vegetables, cereals, pulses, oil seed crops, fiber crops, sugarcane, spices, and ornamentals are cultivated in India. Virus diseases and their vectors are also in abundance. Since ancient times, virus-like diseases and management practices have been known in India. This knowledge has now been revived and adopted in organic farming, especially for medicinal and aromatic plants. Current trends for extensive and intensive agriculture, open international agricultural trade, and thus food security and sustained economy have brought new challenges in the fight against virus diseases. In this changing scenario, current diseases of significance are caused by begomoviruses, badnaviruses, cucomoviruses, potyviruses, ilarviruses in crops such as vegetables, fruits, ornamentals, fiber crops, and sugarcane. Variability in the viruses is also common. Briefly reviewed here is the positive effect of an isolate of Rice necrosis mosaic virus; when artificially inoculated on jute and mesta fiber crops enhanced their fiber contents. Diseases of significance, e.g., leaf fleck disease of sugarcane, citrus yellow mosaic disease, banana bunchy top, banana bract mosaic, mungbean yellow mosaic, mosaic in chrysanthemum, gladiolus and orchids are also discussed. Efficient, reliable diagnostic tools have been developed and used extensively. Some of the advanced laboratories have been accredited for virus indexing under the National Certification System for tissue-cultured plants. International standards for phytosanitary measures have been promulgated, and a mandatory nodal agency is in place for the conservation and exchange of germplasm; a Containment Level-4 facility to examine incoming transgenics and a fully equipped laboratory to intercept virus-infected plant material are functional. A National Agricultural Biosecurity System will soon be in place. All these measures are essential to protect agricultural systems and to compete in the international agriculture market. Continued vigilance, disease mapping and adopting the latest technology are required to practice sustainable agriculture.