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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 Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).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 morindae Z.G. Abad & S.C. Nelson 2010 (Oomycetes, Pythiales)
Distribution: USA: HI.
Disease Note: Black flag disease.
Host: Morinda citrifolia var. citrifolia (Rubiaceae).
Supporting Literature:
Nelson, S. C., and Abad, Z. G. 2010. Phytophthora morindae, a new species causing black flag disease on noni (Morinda citrifolia L) in Hawaii. Mycologia 102: 122-134.
Updated on Feb 04, 2010
Phytophthora morindae Z.G. Abad & S. C. Nelson was initially recovered from Morinda citrifolia var. citrifola (Indian mulberry) in Hawaii (Nelson and Abad 2010). Phylogenetic analysis with the ITS region of the rDNA and translation elongation factor 1 alpha place it in clade 10 closely related to P. kernoviae.
1. Sporangia
Sporangia were produced abundantly in solid media, including baby carrot agar, baby lima bean agar and water cultures, and formed in umbellate sporangiophores (Fig. 1). Sporangia had conspicuous papillae, usually one but were occasionally bipapillate, were ellipsoid, ellipsoid with tapered base, obpyriform, limoniform or asymmetrical (bilaterally symmetrical or mouse shape with one rounded and one flatter side) 30–54 (average 42) µm long, 19.2–24 (average 21.8) µm wide, and were caducous with variable length of pedicels 8–66 (average 26) µm (Fig. 2). Zoospores produced after stimulation of low temperature (5° C, 10 min) and light.
2. Chlamydospores
Chlamydospores and hyphal swellings are absent in water or culture media.
3. Sex Organs
Sexual stage was homothallic, abundantly producing oogonia in culture media baby carrot agar, baby lima bean agar, frequently with tapered bases and 21.6–39.6 (average 30.4) µm diam (Fig. 3). Antheridia were amphygynous and small at 7.2–14.43 6–12 (average 11.2 - 8.5) µm. Oospores were plerotic, 21–38.9 (average 30.3) µm diameter with wall thickness 2.4–3.6 (average 3.2) µm. Immature oospores showed the presence of thick walls and mature oospores had thinner walls at 2.4–3.6 (average 3.2) µm. Large ooplasts in mature oospores were frequently present, 13.2–20.4 (average 3.2) µm diam.
4. Growth Temperatures
Minimum for growth on B-LBA is 10° C, optimum 20° C, maximum 27° C. Colonies on baby lima bean agar slow growing, growth 2.9 mm/ d21 at 20° C.
5. Growth Characteristics in Culture
Phytophthora morindae colonies on PDA developed moderate aerial mycelia and a fine chrysanthemum pattern at the border of the colony (Fig. 1), colonies on baby carrot agar with aerial mycelia sparse. Mycelium branched and unbranched with curly hyphae frequently observed in baby lima bean agar, main hyphae 3–8 mm wide.
6. Distinguishing Characteristics
The morphology of sexual reproductive structures of P. morindae and P. kernoviae are similar, but the umbellate sporangiophores of P. morindae differentiate it from P. kernoviae.
Phytophtora morindae has been reported only on Morinda citrifolia var. citrifola in Hawaii, where it is capable of causing blight on above ground plant parts (root and stem tissue have not shown symptoms or the ability to recover the pathogen). Severely infected plants have a characteristic black flag consisting of diseased leaves. In the early stages of disease the leaves may have black streaks alongside the veins caused by rapid colonization by the pathogen. Fruit infection often occurs through the pedicel and can result in shriveled fruit mummies remaining attached to the stem.
Nelson, S. C., and Abad, G. Z. 2010. Phytophthora morindae, a new species causing black flag disease on noni (Morinda citrifolia L) in Hawaii. Mycologia 102:122-134.
This species page was adapted from Nelson et al. (2010)
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