Identification and Detection ofPhytophthora: Reviewing Our Progress, Identifying Our Needs

Abstract

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.

A unique species in Phytophthora clade 10, Phytophthora intercalaris sp. nov., recovered from stream and irrigation water in the eastern USA

“…Clade 3 contains four homothallic species; all produce semipapillate and caducous sporangia (Kroon et al, 2012;Martin et al, 2012). All four clade-5 species are homothallic and produce papillate and non-caducous sporangia (Kroon et al, 2012;Martin et al, 2012;Weir et al, 2015). Previous studies have suggested that morphological features, especially papillation, are mostly consistent within individual clades or subclades (Kroon et al, 2012;Martin et al, 2012;Yang, 2014).…”

“…Even with the addition of P. intercalaris, Phytophthora clade 10 now includes only five formal species. The two other clades that contain fewer species are clades 3 and 5 (Kroon et al, 2012;Martin et al, 2012;Weir et al, 2015). Clade 3 contains four homothallic species; all produce semipapillate and caducous sporangia (Kroon et al, 2012;Martin et al, 2012).…”

“…The two other clades that contain fewer species are clades 3 and 5 (Kroon et al, 2012;Martin et al, 2012;Weir et al, 2015). Clade 3 contains four homothallic species; all produce semipapillate and caducous sporangia (Kroon et al, 2012;Martin et al, 2012). All four clade-5 species are homothallic and produce papillate and non-caducous sporangia (Kroon et al, 2012;Martin et al, 2012;Weir et al, 2015).…”

“…The genus Phytophthora currently includes more than 130 species (Kroon et al, 2012;Martin et al, 2012Martin et al, , 2014. Although species of Phytophthora resemble filamentous fungi morphologically, they actually belong to the kingdom Chromalveolata, which is more closely related to plants and algae (Adl et al, 2005).…”

Phytophthora niederhauserii sp. nov., a polyphagous species associated with ornamentals, fruit trees and native plants in 13 countries

“…During this time an increasing number of damaging species have been described in various ecosystems. For example, P. ramorum, P. pinifolia and P. kernoviae are notable for the economic and environmental damage they have caused in natural ecosystems and nursery production (Brasier et al 2005, Brasier and Webber 2010, Duran et al 2008, Hansen et al 2012, Martin et al 2012. Several new species also have been found during surveys targeting the quarantine pathogens above (Ersek andRibeiro 2010, Kroon et al 2012).…”