Obligate biotrophic plant pathogens exhibit a highly evolved relationship with their hosts, being completely dependent on living host tissue for survival. Many of the most destructive plant pathogens are obligate pathogens, including the downy mildews, powdery mildews and rusts. The maize downy mildews Peronosclerospora philippinesis and Sclerophthora rayssiae and the soybean rust Phakopsora pachyrhizi are considered major crop biosecurity threats to the US. However, genetic analysis of obligate biotrophs is difficult because they cannot be grown apart from their plant hosts. As part of an international initiative a draft genome sequence will be developed for Peronospora parasitica, a downy mildew of Arabidopsis thaliana and placed into a community annotation database. UK collaborators will carry out sequencing of ESTs and fingerprinting and sequencing of BAC clones. Pe. parasitica is a compelling choice for studying obligate biotrophy. Firstly it has culturable close relatives, such as Phytophthora infestans and Phytophthora sojae, that have excellent genome resources and are amenable to genetic manipulation, facilitating functional analysis of Pe. parasitica genes. Secondly, the host of Pe. parasitica, Arabidopsis is the leading plant model system, so that there has already been extensive physiological, genetic and genomics studies of the interaction between Pe. parasitica and its host.
Broader Impacts The project will also create a resource for the plant-microbe interaction research community that will enable significant advances in the understanding of how biotrophic pathogens attack plants, and consequently, the design of better methods for protecting crops and natural ecosystems from these pathogens. The community annotation platform and annotation jamboree will provide multi-disciplinary training environments for postdoctoral fellows, graduate students, undergraduates from all US and international institutions.
