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Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022

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Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott in Dobbie et al., Forests 13 [7] (2022)
Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022

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Endemic
Present
New Zealand
Political Region
A pathogen of totara trees in the North Island [BSW, 1 Feb 2022]

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K. Dobbie, R.L. McDougal & P.M. Scott
K. Dobbie, R.L. McDougal & P.M. Scott
2022
[7]
ICN
Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022
species
Phytophthora podocarpi
‘podocarpi’ refers to Podocarpus, the host genus of this oomycete

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podocarpi

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Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022

Homothallic, gametangia is rare to absent after 8 weeks and only developed on CA. Oogonia are globose and smooth-walled with a range of mean diam. of 25–30 µm (mean diam. 27.4 µm ± 1.0) with a common range of 20–33 µm. Oogonial stalks are often globose, occasionally with digitate projections. Antheridia areapparently absent, and when present, paragynous and single, mostly globose to club shaped, with a range of means 5–10 × 6–10 µm and a common range of 5–15 × 4–10 µm. Oospores are plerotic with a diameter range of 22–27 µm (mean diam. 24.8 µm ± 1.0) and a common range of 18–30 µm; it has a wall thickness average of 2 µm and a common range of 1–3 µm. Sporangia borne on simple or compound sympodial sporangiophores are often clustered and form readily within CA, and are less abundant in the aerial mycelium. Sporangia produced from filtered pond water after 72 h are ovoid, obpyriform to limoniform; nonpapillate to semi-papillate; and persistent and caducous with short length (1–4 µm) pedicels. Sporangia’s range of means are 47.6–64.5 × 31.3–41.1 µm (mean length 55.7 µm ± 12.2 and breath 37.0 µm ± 8.2) and it has a common range 22–79 × 15–54 µm. Its length to breadth ratio average is 1.5. No internal or external proliferation was observed. The mycelium on CA has a thickness that is highly variable, from 5–12 µm. It is often prominently constricted at branching, with a resulting swollen wide hypha from the constriction. A few swellings and knot type structures were observed, and no chlamydospores were observed on CA. Colonies in the dark at 17 ◦C after 28 days experienced slow growth, and were lightly felted with sparse aerial mycelium, loosely striate, and even radial growth. Under continuous light at 17 ◦C after 28 days, they experienced slow growth, were lightly felted with an aerial mycelium which was denser in the centre, becoming sparse towards the growing margin, as well as being distinctly striate, and even experiencing radial growth (Figure 5). The optimum growth rate was 17 ◦C. There was no growth or minimal growth at 2 and 25 ◦C. At 17 ◦C in darkness, a radial growth of ca 1.0–1.2 mm d−1 (mean 1.1 mm d−1) occurred.
NEW ZEALAND: Gisborne: Hampton Forest, from needles of Podocarpus totara, July 2011, Collected by B. J. Rogan, holotype NZFRIM 5991 (dried culture on CA, Scion, Rotorua) ex holotype living culture permanently preserved in a metabolically inactive state as ICMP 24118 = NZFS 3642. Genome sequence GenBank LGSN00000000
The disease caused by PTT is now known as tōtara needle blight. The affected trees exhibit needle dieback in the lower crown. Infected needles initially turn khaki in colour then blacken and cast. Shoot infection causes the needles above the point of infection to brown and these needles are retained, giving the trees a fired, scorched appearance (Figure 2). Typically, symptoms are observed during winter and spring.

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Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022
Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott
Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022
Phytophthora sp. "taxon Totara" McDougal 2016
Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022

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Phytophthora podocarpi K. Dobbie, R.L. McDougal & P.M. Scott 2022
[Not available]

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Etymology
‘podocarpi’ refers to Podocarpus, the host genus of this oomycete

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2474d618-af90-42aa-9bb6-cf74ca7703cd
scientific name
Names_Fungi
1 February 2022
2 May 2022
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