This broad area is a vibrant and fast developing area of plant biology and pathology which has been mostly neglected in various botanical, ecological and plant pathology meetings. The 14 papers in this volume cover this wide range of topics and have been arranged according to the main subject matter, i.e. from the theoretical background to the practical applications in resistance breeding and disease control. As such this volume represents the first comprehensive treatment of this topic in a plant pathology-focused scientific journal.