Root diseases are a major global threat to sustainable agricultural production. Complexes of interacting soilborne fungal, oomycete and nematode pathogens are involved in causing these diseases that are generally termed root disease complexes. These soilborne pathogen complexes typically have resilient long-term survival mechanisms, the ability to cross-infect multiple crop genera and species, and a wide range of spatial dispersal modes. Although, in some instances, individual pathogens within a complex have been identified using classical and molecular techniques, in most cases the full range of pathogens involved in root disease complexes remain undefined. At the molecular level, it is increasingly obvious that different pathogens engage unique sets of proteins to infect hosts successfully. In addition, the unpredictable and ever-changing nature of soilborne pathogens in space and time challenges their management. A better understanding of the whole system dynamics of root disease complexes is thus a prerequisite for their effective management, especially under climate change scenarios. Management of root disease complexes is dependent upon improved detection and diagnostic techniques that accurately define the full pathogen complement involved, along with an improved understanding of the evolution of root disease complexes, their epidemiology, and adaptation across multiple hosts within wide-ranging and dynamic agricultural systems. This review will focus on root disease complexes of arable crops, with particular emphasis on diagnosis, pathogen genetic diversity, epidemiology, management options, and, how root and airborne diseases interact, and will identify future scope of research.
