Identification and Detection of Phytophthora: Reviewing Our Progress, Identifying Our Needs
- Frank N. Martin , USDA, ARS, Crop Improvement and Protection Research Unit, Salinas, CA
- Z. Gloria Abad , USDA, APHIS, PPQ, Center for Plant Health Science and Technology (CPHST), Beltsville Laboratory, MD
- Yilmaz Balci , Department of Plant Sciences and Landscape Architecture, University of Maryland, College Park, MD
- Kelly Ivors , Department of Plant Pathology, NC State University, Mountain Hort. Crops Research & Extension Center, Mills River, NC
With the increased attention given to the genus Phytophthora in the last decade in response to the ecological and economic impact of several invasive species (such as P. ramorum, P. kernoviae, and P. alni), there has been a significant increase in the number of described species. In part, this is due to the extensive surveys in historically underexplored ecosystems (e.g., forest and stream ecosystems) undertaken to determine the spread of invasive species and the involvement of Phytophthora species in forest decline worldwide (e.g., oak decline). The past decade has seen an approximate doubling in the number of described species within the genus Phytophthora, and the number will likely continue to increase as more surveys are completed and greater attention is devoted to clarifying phylogenetic relationships and delineating boundaries in species complexes. The development of molecular resources, the availability of credible sequence databases to simplify identification of new species, and the sequencing of several genomes have provided a solid framework to gain a better understanding of the biology, diversity, and taxonomic relationships within the genus. This information is much needed considering the impact invasive or exotic Phytophthora species have had on natural ecosystems and the regulatory issues associated with their management. While this work is improving our ability to identify species based on phylogenetic grouping, it has also revealed that the genus has a much greater diversity than previously appreciated.