ABSTRACT Molecular Plant-Microbe Interactions 9, 443-449.

The oomycetes are a group of diverse organisms that in-dude significant pathogens of plants, insects, and animas as well as saprophytic species. oomycetes infecting plants in-elude obligate pathogens, such as the downy mildews and the white rusts, and facultative pathogens within the genera Phytophthora and Pythium. The need to Learn more about the biology and pathology of the oomycetes has been long recognized, and it is likely that such studies will yield novel biological findings as oomycetes do not share a close taxonomic affinity with more intensely studied organisms. For example, contemporary assessments of phylogenetic relationships based on rRNA sequence comparisons indicate that oomycetes are more closely related to chrysophytes, diatoms. and heterokont algae than to ascomycetes and basidiomycetes, despite the linkage of oomcyeetes to other fungi in traditional classifia-tion schemes. Until recently, research studies of oomycetes were hampered by the unavailability or inefficiency of methods for genetic investigation. Oomycetes are consequently less well characterized as a group than are other fungi such as ascomycetes-and basidiomycetes, for which sophisticated procedures for molecular and classical genetic analyses have been avail-able for many years. Doc to improvements to the repertoire of genetic techniques available for the oomycetes, the potential exists to make rapid advances in our understanding of these important organisms. This review provides an update on the current status of oomycete genetics and its application to the study of plant-microbe interactions.