Application of recombinant DNA technology to plant protection: molecular approaches to engineering virus resistance in crop plants.

Developments in plant tissue culture, plant transformation and regeneration, and improvements in techniques to isolate and manipulate viral genes have led to the exploitation of the concept of 'cross protection': turning the virus onto itself and controlling it with its own genes. By introducing and expressing genes of viral origin in crop plants, scientists have engineered resistance to several plant viruses. Some of the approaches, used singly or in combination, include expression of viral-coat protein, untranslatable sense or antisense RNA, satellite RNA, virusspecific 'neutralizing' antibody genes, plant viral replicase, protease or movement proteins and defective, interfering RNA. All of these approaches have resulted in manifestation of virus resistance to varying degrees in several commercially important crop plants. This review summarizes the recent advances in engineering virus resistance using the above approaches, and lists specific examples of their use in cultivated crop plants of economic importance.