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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 kernoviae Brasier, Beales & S. A. Kirk was previously known as the provisional species Phytophthora taxon C (PtC). It has been recovered from Southwest England and New Zealand and in phylogenetic analysis is placed in clade 10 with P. boehmeriae as the closest relative.
1. Sporangia
Sporangia occasional on CA in the light. Produced abundantly on CA plugs immersed in unsterile pond water or soil leachate; with sympodial sporangiophores. Papillate, caducous, from regular ovoid or limoniform to distinctly asymmetrical or ‘mouse-shaped’ with one rounded and one flatter side. Most have a conspicuous vacuole. Sporangia length:width range of means ca 38.5–45.5 x 22.5–27 µm, common range ca 34–52 x 19–31 µm. Length:width ratio average ca 1.5 µm. Sporangial pedicels range of means ca 8.6– 14.1 µm, common range ca 5–19 µm.
2. Chlamydospores
No chlamydospores observed.
3. Sex Organs
Homothallic, gametangia usually frequent to abundant after 10 d on CA. Oogonia, diameter range of means 23.5–25.5 µm, common range ca 21–28 µm; often with tapered stalks. Antheridia amphigynous. Antheridial length:width range of means ca 11.5–12.5 x 10–10.5 µm, common range ca 10–14 x 9–12 µm. Oospores plerotic, diameter range of means ca 21.1–22.5 µm, common range ca 19–25 µm; wall thickness average ca 3.5 µm, common range 3.5–5 µm.
4. Growth Temperatures
Optimum temperature for growth on CA, ca 18° C. Upper temperature limit for growth ca 26° C. Growth rate at 20° C in darkness ca 3.8–4.6 mm/day.
5. Growth Characteristics in Culture
Colonies on CA (10 d at 20° C in darkness) largely submerged. On subsequent exposure to light, with a small central boss of patchy aerial mycelium. In diurnal light, with alternating rings of aerial mycelium. Some isolates degenerate during subculturing on artificial media to produce irregular, sectoring colonies or faster striate colonies with lobes of denser aerial mycelium. Hyphae sometimes denticulate or tuberculate.
6. Distinguishing Characteristics
P. kernoviae can be distinguished from other homothallic Phytophthoras with caducous papillate sporangia and medium length pedicels as follows: from P. botryosa and P. heveae by its much lower optimum and maximum temperatures for growth; and from P. nemorosa by its higher optimum temperature for growth. It can also be distinguished from P. meadii, P. botryosa and P. nemorosa by its often tapered oogonial stalks; P. meadii, P. megakarya and P. nemorosa by its often asymmetric sporangia; and from P. boehmeriae (its possible nearest relative) by its much longer sporangial pedicels.
Phytophthora kernoviae has been associated with bark necrosis and bleeding stem lesions above ground level (‘ aerial stem lesions ’) on European beech, Fagus sylvatica. It has also been isolated from similar lesions on Quercus robur and Liriodendron tulipifera. The lesions often develop into sunken or erumpent bark cankers. P. kernoviae is also especially associated with shoot dieback, foliar necroses and wilting of rhododendron, notably Rhododendron ponticum. Dieback is often observed on both lower and upper stems. Leaves may abscise rapidly, leading to defoliation. In particularly severe infections, the shrub is killed. P. kernoviae also causes foliar necroses of Magnolia spp., Pieris formosa, Gevuina avellana, Camellia spp. and Michelia doltsopa, and leaf and shoot dieback of Q. ilex.
Brasier, C. M., Beales, P. A., Kirk, S. A., Denman, S. and Rose, J. 2005. Phytophthora kernoviae sp. nov., an invasive pathogen causing bleeding stem lesions on forest trees and foliar necrosis of ornamentals in the UK. Mycol. Res. 109: 853–859
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS. This species page was adapted from Brasier et al. (2005)
Isolate list