Foreword -- Progress and challenges in systematics of downy mildews and white blister rusts: new insights from genes and morphology -- Classical and molecular genetics of Bremia lactucae, cause of lettuce downy mildew -- Species hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review -- Proteomic analysis of a compatible interaction between Pisum sativum (pea) and the downy mildew pathogen Peronospora viciae -- Tapping into molecular conversation between oomycete plant pathogens and their hosts -- Diversity of defence mechanisms in plant-oomycete interactions: a case study of Lactuca spp. and Bremia lactucae -- Natural history of Arabidopsis thaliana and oomycete symbioses -- Comparative epidemiology of zoosporic plant pathogens -- Structure and variation in the wild-plant pathosystem: Lactuca serriola-Bremia lactucae -- Development of detection systems for the sporangia of Peronospora destructor -- Fungicide modes of action and resistance in downy mildews -- Activity of carboxylic acid amide (CAA) fungicides against Bremia lactucae -- Beta-aminobutyric acid-induced resistance in grapevine against downy mildew: involvement of pterostilbene -- Effects of garlic (Allium sativum) juice containing allicin on Phytophthora infestans and downy mildew of cucumber caused by Pseudoperonospora cubensis. Knowledge of downy mildew pathogens and diseases has increased significantly in taxonomy, phylogeny, genetics, molecular biology, host-parasite interactions, ecology, epidemiology and control. The opportunity to update comprehensively the major advances in these areas was created by the 2nd International Symposium on Downy Mildews held in July 2007 at Olomouc (Czech Republic). Keynote contributions from this meeting are published here in 14 chapters that provide the most authoritative and recent analysis of these biotrophic plant pathogens and their interactions with plants. It will be an invaluable resource to students and researchers in plant pathology, mycology, taxonomy, plant biology and crop protection.