ABSTRACT
In vitro culture and selection of plant cells and tissues has been used effectively as a tool for developing novel, disease-resistant genotypes. The first demonstration of this technique was to produce wildfire-resistant tobacco plants through in vitro selection by using methionine sulfoximine, a structural analog of wildfire toxin. Since then, plant cells have been successfully selected against an array of pathogenic microorganisms and regenerated into plants with enhanced disease resistance. In addition, plant cell and tissue culture has become an important tool in the study of plant-pathogen interactions at the cellular and molecular levels. Plant cells react to certain biotic and abiotic stresses in a
manner similar to that of an intact plant. This makes such cell cultures ideal candidates to understand the resistance responses and changes occurring at the cellular and subcellular levels, when infected with pathogenic organisms (Jayasankar, 2000). Some of the common responses that are well documented include changes in permeability of plasma membrane and triggering the synthesis of new biochemical compounds, especially defense-related enzymes (such as the pathogenesisrelated proteins; see Chapter 28). Plant cell cultures provide an ideal population of homogeneous genetic material. A single flask of embryogenic cell suspension culture theoretically represents millions of plants that can be effectively screened. For instance, a suspension culture of grape proembryogenic masses (Figure 38.1) contains enough totipotent cells to regenerate plants for hundreds of acres of vineyard. Furthermore, the culture is very useful to perform a number of genetic tests such as bioassays and can also be useful to culture biotrophic pathogens. This chapter will address how in vitro culture can be best used to study and understand plant pathogen interactions.
