This book deals with the structure and replication of plant viruses, viroids, satellites of plant viruses, and spiroplasmas and neatly sums up the state of our knowledge about these aspects of these pathogens.Published information about single-stranded positive-sense RNA plant viruses is far greater than for any other group of plant pathogens.The book caters to the needs of students as well as researchers and is illustrated with micrographs, figures of postulated models, and genetic maps