Plant defence signalling response against various pathogens, including viruses, is a complex phenomenon. Interaction between plant and pathogen can be studied with the help of systems biology approach. Systems biology is a relatively new biological study field that focuses on the systematic study of complex interactions in biological systems. The use of systems biology to integrate across transcriptomics, metabolomics, and genomics is significantly enhancing the rate of discovery of genes, metabolites, and bioactivities for plant defense compounds as well as extending our knowledge of how these compounds are regulated. Systems biology may provide a framework to fill the gap by predicting pathogen and host fitness and their evolution. Current edition of this book is most useful to students, teachers and scientist across the world those who are working on the plant pathogen interactions studies.