Phytophthora has been rebuilt to fix security-related problems and to restore GIS tools. These tools allow users to visualize the geospatial, temporal, and environmental contexts of Phytophthora discoveries. The next phase is to update species information and add data derived from large-scale surveys. If you have suggestions and requests to make the database better, please contact Seogchan Kang (sxk55@psu.edu).
Genus wide phylogeny for Phytophthora using four mitochondrial loci (cox2, nad9, rps10 and secY; 2,373 nucleotides). Maximum likelihood branch lengths shown. Numbers on nodes represent bootstrap support values for maximum likelihood (top), maximum parsimony (middle) and Bayesian posterior probabilities as percentages (bottom). Nodes receiving significant support (>95%) in all analysis are marked with an asterisk (*). Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).
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Phytophthora rosacearum E.M. Hansen & Wilcox has been referred to as the ‘‘high temperature/small oogonia’’ group of P. megasperma s.l. (Wilcox and Mircetich 1987) and the AC, or apple-cherry protein group (Hansen et al 1986). A detailed morphological evaluation (Hansen et al. 2009) and phylogenetic analysis confirms it is a distinct species in clade 6 basal to P. megasperma, P. gonapodyides and many other clade 6 species.
1. Sporangia
Sporangia are ovoid or obpyriform, nonpapillate, with a slight apical thickening, and about 56 µm long, with a length to width ratio of 1.5. Sporangia form in water on loosely sympodial sporangiophores(Fig. 1). Proliferation is typically internal, occasionally lateral from beneath the sporangium.
2. Chlamydospores
Chlamydospores are not formed in agar.
3. Sex Organs
Phytophthora rosacearum is homothallic, with predominately paragynous antheridia(Fig. 1). Oogonia average 29–34 µm diameter (range of isolate means).
4. Growth Temperatures
Radial growth on CMA at 25 C is about 6 mm/d, with a growth optimum at 30 C and a maximum temperature for growth at 36 C.
5. Growth Characteristics in Culture
A distinctive strongly petaloid colony pattern develops on carrot agar (illustrated in Hansen et al 1986).
6. Distinguishing Characteristics
P. rosacearum is morphologically similar to the species in Waterhouse (1963) group 5, hence its early misidentification as P. megasperma. It is most readily distinguished from P. megasperma s.s. and morphologically similar species by its distinctive strongly rosette-petaloid colony morphology when grown on CA (illustrated in Hansen et al 1986 and Brasier et al 2003), as well as its higher growth temperature. It differs from P. gonapodyides and other self-sterile species in ITS clade 6 by its homothallism and from the homothallic members of the clade by its distinctive colony morphology.
Phytophthora rosacearum is an important pathogen of rosaceous fruit trees, including apple and cherry in California, apple in New York, apricot in Maryland and peach in Ohio (Hansen et al 2009).
Brasier, C., Cooke, D. E. L. , Duncan, J. M., Hansen, E. M. 2003. Multiple new phenotypic taxa from trees and riparian ecosystems in Phytophthora gonapodyides-P. megasperma ITS Clade 6, which tend to be high-temperature tolerant and either inbreeding or sterile. Mycol. Res. 107:277–290.
Hansen, E. M., Wilcox, W. F., Reeser, P. W., Sutton, W. 2009. Phytophthora rosacearum and P. sansomeana, new species segregated from the Phytophthora megasperma ‘‘complex’’. Mycologia 101:129-135.
Hansen, E. M., Brasier, C. M. , Shaw, D. S., Hamm, P. B. 1986. The taxonomic structure of Phytophthora megasperma: evidence for emerging biological species groups. Trans. Br. Mycol. Soc. 87:557–573.
Waterhouse, G. M. 1963. Key to the species of Phytophthora de Bary. Mycological Papers 92. Commonwealth Mycological Institute, Kew, UK.
Wilcox, W. F., Mircetich, S. M.. 1987. Lack of host specificity among isolates of Phytophthora megasperma. Phytopathology 77:1132–1137.
This species page was adapted from Hansen et al. (2009)
Isolate list