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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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 glovera Z.G. Abad & Shew 2011 (Oomycetes, Pythiales)
Distribution: Brazil.
Disease Note: Root rot, stunting.
Host: Nicotiana tabacum (Solanaceae).
Supporting Literature:
Abad, Z.G., Ivors, K.L., Gallup, C.A., Abad, J.A., and Shew, H.D. 2011. Morphological and molecular characterization of Phytophthora glovera sp. nov. from tobacco in Brazil. Mycologia 103: 341-350.
Updated on Jul 19, 2011
Phytophthora glovera Z.G. Abad & H.D. Shew was isolated consistently from roots of cultivated tobacco affected with a yellow stunt disease known as Amarelao in Brazil. Phylogenetically it is in clade 2 related to P. capsici.
1. Sporangia
Sporangia are readily produced on sections of infected root pieces or agar plugs under water culture, 10% soil solution and on solid media. Sporangia range from ovoid, obpyriform, obclavate, sub-globose, to irregular and distorted, 43–61 (av. 50) µm long by 26–36 (av. 32) µm wide. Sporangia are persistent and frequently attached laterally to the sporangiophore and are produced in unbranched simple sporangiophores or in simple sympodial pattern in sporangiophores originated laterally or apically in a previous sporangium. Typical sporangia produced under water blank cultures are semi-papillate, with apical thickening of 7–9 µm (av. 8 µm), and an exit pore of about 7–9 (av. 7 µm). Occasionally sporangia with two (bilobed) or three (trilobed) apices are produced. Some sporangia show a prominent papilla before liberation of zoospores. Sporangia are mostly terminal and germinate either directly or indirectly. Encysted zoospores are ca. 8.6 µm diam.
2. Chlamydospores
Chlamydospores and hyphal swellings are not produced in culture media or in water cultures.
3. Sex Organs
Phytophthora glovera is homothallic, and oospores are produced abundantly in single-strain culture in all media and occasionally in diseased host tissues. Oospores with a single antheridium are paragynous, or amphigynous. Two antheridia per oogonium are sometimes (ca. 10%) double paragynous and paragynous- amphigynous. Some unusual tooth shaped or finger-like projections from paragynous or amphigynous antheridia are observed frequently. Paragynous antheridia are 7–11 (av. 9.5) µm wide, amphigynous antheridia 10–11 (av. 10.7) µm wide. Oogonia are smooth-walled and hyaline (when young) to dark yellow to orange (when old), 26–41 (av. 34) µm diam. Oospores are markedly aplerotic (do not fill the oogonial content), 23–30 (av. 27) µm diam, with a wall 4–6 (av. 5) µm thick. The presence of oospores positioning at one side of the oogonium also is observed. Germination of oospores by production of sporangia attached to the oogonia wall has been determined.
4. Growth Temperatures
Phytophthora glovera has moderately slow growth at 25° C on CA with a radial growth about 5.4 mm/d, on C-CA about 5.2 mm/d, on V8A about 3.6 mm/d, slow growth on CMA with about 1.8 mm/d and on PDA about 0.8 mm/d. On CMA isolates grew at 13– 30° C with an optimum at 25° C.
5. Growth Characteristics in Culture
Colonies on CA and V8 (clarified and non-clarified) all adhered to the substrate with growth with slight stellate pattern at the center and uniform pattern at the border of the colony. This pattern was less obvious on CMA. Main hyphae in CMA were 3–6 µm wide. Hyphal rings intercalary in the mycelium or connected with sporangia sometimes are observed.
6. Distinguishing Characteristics
Morphologically P. glovera is similar to P. multivora in the sporangia, which are ovoid and present up to two papillae. Both species can also be differentiated based on sexual reproductive structures; P. multivora produces predominantly paragynous and rarely amphigynous antheridia, while P. glovera produces both amphigynous or paragynous antheridia and both types of antheridia are frequently observed on a single oogonium. In addition P. multivora produces mostly plerotic oospores, while P. glovera produces mostly aplerotic oospores.
P. glovera causes a yellow stunt disease known as Amarelao in Brazil, and while the primary symptom was root rot, the disease never progressed to the stem as is observed with the black shank disease of tobacco caused by P. nicotianae.
Abad, Z. G., Ivors, K. L., Gallup, C. A., Abad, J. A., Shew, H. D. 2011. Morphological and molecular characterization of Phytophthora glovera sp. nov. from tobacco in Brazil. Mycologia, 103: 341–350.
Nomenclature information was provided by the the Systematic Botany and Mycology Laboratory in USDA-ARS.
This species page was adapted from Abad et al. (2011).
Isolate list