ABSTRACT
Host resistance is one of several classical approaches to virus disease control. The others are cure of the disease, maintenance and use of pathogen-free seed or propagules, restriction of long-distance movement of the pathogen into new areas, restriction of local dissemination into and among crop plants, and restriction of deleterious effects of disease. This chapter describes various aspects of both classical cross-protection and genetically engineered protection in order to emphasize the similarities and differences between the approaches. It discusses the significance and relative effectiveness of the approaches. A potential area of confusion arises because the term is now applied to describe both the presumed cause and effect of the phenomenon. Protection against virus infection can also be achieved by expression of viral satellite RNAs in plants. Plants expressing satellite RNA are tolerant to viral infection, whereas plants expressing coat protein are resistant or immune in many cases.
