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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 pini Leonian, 1925 Emend. Gallegly, Hong, Richardson & Hong 2008 was initially noted in 1925 as the species name of an isolate recovered from red pine (Pinus resinosa) in Minnesota but a formal Latin description was not done. In her compilation of her original descriptions of the genus Waterhouse (1956) felt this species was the same as P. citricola, which did have a formal description (Ito and Tokunaga 1935)and hence had precedence as a name. Recent work has confirmed distinct phylogenetic lineages are present in the P. citricola species complex and P. pini has been resurrected (Hong et al. 2011).
1. Sporangia
The noncaducous semipapillate sporangia are mostly ovoid (Fig 1G-H). However ellipsoid, bluntly ellipsoid and bizarre shapes occur in 10% soil extract. Sporangia averages 47.4 - 31.5 µm (l/b ratio is 1.52 and the range is 31.5–75.3 3 21.7–49.5 µm). Sporangia produced on lima bean agar are 56.8 µm long and 36.6 µm wide, larger than those on clarified V8 agar. First-flush sporangia are larger and tend toward being ellipsoid, whereas sporangia produced later are smaller and ovoid. Simple sympodia occur, sometimes close but mostly loose. Major character differences were observed among the four isolates assessed
2. Chlamydospores
Chlamydospores have not been seen, but a few small hyphal swellings and irregular hyphae(Fig 1F) sometimes occur in lima bean agar.
3. Sex Organs
Homothallic with paragynous antheridia (Fig 1A-E). Oogonia produced on clarified V8 agar or hempseed agar are globose and relatively uniform, averaging 30.3 µm diameter (range 22.2–41.4 µm diameter). Oospores are mostly plerotic and average 26.0 µm diameter (19.6–34.2 µm diameter), their cell walls are 1.7 mm thick (1.4–1.9 µm). The antheridial characters differ from those of P. citricola s.s. The antheridia are larger, capitate to slightly asymmetrically capitate, diclinous, and attached at the base near the oogonial stalk. Occasionally two antheridia per oogonium may be seen. Antheridia are 11.1 µm tangential to the oogonial wall (range 10.2–12.9µm) and 12.6 µm perpendicular to it (10.2–15.0 µm).
4. Growth Temperatures
Temperature optima 25° C, does not grow at 5° C with a temperature maximum above 30° C.
5. Growth Characteristics in Culture
6. Distinguishing Characteristics
The optimum temperature for P. plurivora and P. pini was 25° C, in comparison it was 20–25° C for P. citricola s.s. P. plurivora grew 0.4 µm per d at 5° C, but P. citricola s.s. and P. pini did not grow. P. citricola s.s. and P. plurivora grew only during the first 2 d at 30° C, indicating this is their maximum growth temperature. In contrast P. pini grew at 30° C.
P. citricola s.s. and P. pini are similar morphologically. They both have globose oogonia about 30 µm diameter and plerotic oospores with walls about 1.5–1.7 µm thick. Their antheridia however are different, particularly in size and shape. Those of P. pini are larger, 11.1 µm tangential to the oogonial wall and 12.6 µm perpendicular to the wall, whereas those of P. citricola s.s. are round and 10 µm or less diam. Also the antheridia of P. pini are capitate, usually slightly asymmetrical. In addition P. pini formed a few small hyphal swellings and occasional clumps of irregular hyphae, whereas P. citricola s.s. did not.
Phytophthora pini is established in North America and Europe as a pathogen on plants in seven genera. This species also could attack a variety of other ornamental and vegetable plants (Hong et al. 2008) and European beech trees (Jung et al. 2009). It is likely that many isolates identified as P. citricola s.l. in major culture collections in reality are P. pini or P. plurivora. Similarly many plant species currently listed as hosts of P. citricola s.l. might be hosts of P. pini instead. Much work will be needed to elucidate the host ranges of P. pini and other emerging entities from P. citricola s.l.
Phytophthora pini poses a growing threat to the horticulture industry for several reasons. P. pini favors alkaline aquatic environments with the optimum pH of 9 (Kong et al. 2009). This occurs in most agricultural runoff containment basins/irrigation reservoirs for most of the growing season (Hong et al. 2009b). This species consequently has been recovered frequently from irrigation reservoirs and natural waterways in Virginia; some isolates of which were identified as P. citricola s.l. or P. citricola I (Bush et al. 2003, Bush et al. 2006, Ghimire et al. 2009). Considering global water scarcity, the horticulture industry increasingly depends on recycled water for irrigation (Hong and Moorman 2005). Accordingly the risk of this species accumulating and being redistributed through recycling irrigation systems is expected to rise. In addition P. pini was the only species among the 18 isolates from 12 species tested that can establish itself in media without soil (Hong et al. 2008).
Bush, E. A., Hong, C. X., Stromberg, E. L. 2003. Fluctuations of Phytophthora and Pythium spp. in components of a recycling irrigation system. Plant Dis. 87:1500–1506
Bush, E. A., Stromberg, E. L., Hong, C. X., Richardson, P. A., Kong, P. 2006. Illustration of key morphological characteristics of Phytophthora species identified in Virginia nursery irrigation water. Plant Health Prog. doi:10.1094/PHP-2006-0621-01-RS.
Ghimire, S. R., Richardson, P. A., Moorman, G. W., Lea-Cox, J. D., Ross, D. S., Hong, C. X. 2009. An in-situ baiting bioassay for detecting Phytophthora species in irrigation runoff containment basins. Plant Pathol. 58:577–583
Hong, C. X., Gallegly, M. E., Richardson, P. A., Kong, P. 2011. Phytophthora pini Leonian resurrected to distinct species status. Mycologia 103:351-360
Hong, C. X., Richardson, P. A., Kong, P. 2008. Pathogenicity to ornamental plants of some existing species and new taxa of Phytophthora from irrigation water. Plant Dis. 92: 1201–1207
Hong, C. X., Moorman, G. W. 2005. Plant pathogens in irrigation water: challenges and opportunities. Crit. Rev. Plant Sci. 24:189–208
Ito S, Tokunaga Y. 1935. Notae mycologicae Asiae orientalis I. (Mycolgoical notes from eastern Asia). Trans. Sappoor. Nat. Hist. Soc. 14:11–33.
Jung, T., Burgess, T. I. 2009. Re-evaluation of Phytophthora citricola isolates from multiple woody hosts in Europe and North America reveals a new species, Phytophthora plurivora sp. nov. Persoonia 22:95–110.
Kong, P., Moorman, G. W., Lea-Cox, J. D., Ross, D. S., Richardson, P. A., Hong, C. X. 2009. Zoosporic tolerance to pH stress and its implications for Phytophthora species in aquatic ecosystems. Appl. Environ. Microbiol. 75:4307–4314
Waterhouse, G. M. 1956. The genus Phytophthora: diagnoses (or description) and figures from the original papers. Kew, Surrey: Commonw. Mycol. Inst.
This species page was adapted from Hong et al. (2011). The contribution of images and additional content for this page by Dr. C. Hong is gratefully acknowledged.
Isolate list