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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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 gallica T. Jung & J. Nechwatal 2008 (Oomycetes, Pythiales)
Distribution: Europe.
Substrate: Soil.
Supporting Literature:
Jung, T., and Nechwatal, J. 2008. Phytophthora gallica sp. nov., a new species from rhizosphere soil of declining oak and reed stands in France and Germany. Mycol. Res. 112: 1195-1205.
Updated on Nov 17, 2009
Phytophthora gallica T. Jung & J. Nechwatal was initially recovered from two stands in France and Germany ca 240 km apart. In phylogenetic analysis it is in clade 10 related to P. boehmeriae and P. kernoviae.
1. Sporangia
Sporangia produced abundantly in water culture. Borne terminally, on unbranched sporangiophores or more rarely in lax sympodia. Non-papillate, proliferating internally in an extended or more rarely in a nested way. Sporangial shapes obpyriform (35 %), ovoid (24 %), peanut shaped (17 %,) or limoniform (12%). Sporangia averaging 52.5 ± 11 x 27 ± 5 µm (range 30–100 x 19–47.5 µm) with isolate means of 51–54 x 25–29 µm, and a length:breadth ratio of 2 ± 0.5 (range of isolate means 1.9–2.1). Zoospores discharged through an exit pore 7.5–19 µm wide (av. 11.5 ± 3 µm). Direct germination of sporangia common in older water cultures.
2. Chlamydospores
Chlamydospores globose and elongated, pyriform, club-shaped and irregular. Attached terminally or laterally. Globose chlamydospores averaging 47.5 ± 7 µm (range 25–62.5 µm, range of isolate means 47–47.5 µm). Elongated pyriform, club-shaped and irregular chlamydospores averaging 72 ± 19 x 34 ± 7 µm (range 40–125 x 15–50 µm). Most chlamydospores starting to abort a few days after formation. Spherical and irregular hyphal swellings produced in water culture.
3. Sex Organs
Oogonia neither produced in single cultures nor in paired cultures of isolates GAL 1 and GAL 2 or in paired cultures with A1 and A2 tester strains of P. cambivora and P. cinnamomi, and A2 tester strains of P. cryptogea and P. drechsleri.
4. Growth Temperatures
At 20° C Phytophthora gallica colonies grew slowly on CA, V8A, MEA and CMA with 2.1–2.9mm/day. Growth on CA occurred from 5–30° C with an optimum at 20° C (radial growth rate 2.2 ± 0.2 mm/day. No growth at 33 and 35° C. In contrast to P. gonapodyides and P. taxon 'PgChlamydo' both isolates of P. gallica showed no re-growth after 7 d at 35° C when returned to 20° C.
5. Growth Characteristics in Culture
Colonies generally appressed with submerged margins and dendroid sectors of aerial mycelium on CA, largely submerged with a rosaceous pattern on MEA, and faintly stellate with narrow- lobed to chrysanthemum margins on CMA. Primary hyphae on CA 2.5–7.5 µm wide (av. 4.5 ± 1.5 µm).
6. Distinguishing Characteristics
Phylogenetically P. gallica is related to P. kernoviae and P. boehmeriae. P. kernoviae can easily be distinguished from P. gallica by its production of oogonia in single culture, the absence of chlamydospores and hyphal swellings, production of papillate caducous sporangia, different colony growth patterns on CA, and different cardinal temperatures for growth. P. boehmeriae is distinguished from P. gallica by its homothallism, the production of papillate caducous sporangia, the absence of elongated pyriform, club-shaped and irregular chlamydospores, different colony growth patterns and higher cardinal temperatures for growth.
Phytophthora gallica is sterile and has nonpapillate sporangia, therefore it belongs to group VI of the morphological classification system and is more similar to several non-papillate species of ITS clade 6, i.e. P. gonapodyides, P. taxon ‘PgChlamydo’, P. taxon ‘salixsoil’ and P. inundata, all occurring in wet habitats. P. gonapodyides differs from P. gallica in the absence of chlamydospores and hyphal swellings, different colony growth patterns on CA, MEA, and CMA, higher maximum temperature for growth and higher growth rates. P. taxon ‘PgChlamydo’ like P. gallica forms both globose and irregular to pyriform chlamydospores. However, it is clearly distinguished from P. gallica by having markedly smaller chlamydospores, different colony growth patterns on CA, MEA, and CMA, higher maximum temperature for growth and higher growth rates. P. taxon ‘salixsoil’ can easily be separated from P. gallica by the absence of chlamydospores and hyphal swellings in water culture, different colony growth patterns on CA, MEA, and CMA, higher cardinal temperatures for growth, and higher growth rates. P. inundata is another widespread non-papillate Phytophthora species from wet sites. It differs from P. gallica by the heterothallic production of oogonia, the absence of chlamydospores and hyphal swellings, higher cardinal temperatures for growth, higher growth rates, and different colony growth patterns.
Although P. gallica was isolated from soil beneath a declining mature Quercus robur and from the littoral zone of a lake with Phragmites australis and Salix alba as dominants, in pathogenicity tests P. gallica was only weakly aggressive to Q. robur and S. alba, and non-pathogenic to Phragmites australis.
Jung, T., Nechwatal, J. 2008. Phytophthora gallica sp. nov., a new species from rhizosphere soil of declining oak and reed stands in France and Germany. Mycol. Res. 112: 1195-1205.
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS. This species page was adapted from Jung an Nechwatal (2008)
Isolate list