Phytophthora Diseases

Gary W. MoormanPenn State

Plant Pathology & Environmental Microbiology

Late blight of tomato(Phytophthora infestans)

Phytophthora, Oomycetenot a true fungus

HyphaeChlamydosporesSporangiaAntheridia/oogoniaZoospores

Cell walls contain celluloseUsually has 2n chromosomes

Antheridium

Oogonium

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Phytophthora, sexual reproduction

A1 +

A2

mating types required

20-50 Zoospores per sporangium

Sporangium

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Phytophthora

plant pathogens

soil-borne??? …usually plant-borne

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Sporangium

Zoospore Release

Oospore germinatingby germ tubeOospore

Formation

Germinating oosporeby sporangium

Sporangium

Sporangium

ZoosporeReleaseSporangiophore

andsporangia

Zoospores

Oogonium &Antheridium

Life history and disease cycle of Phytophthora

A1 & A2mycelium

Asexualreproduction

Sexualreproduction

Wet conditions, 65F - 70F sporangia within 4 hours

Each sporangium > 20 to 50 zoospores released within 1 hour

Phytophthora activity

Phytophthora dispersal

Short distances

Splash

Wind

Long distances

Movement of

plants or soil

Phytophthora cactorum P. citrophthora P. citricola P. cryptogea P. drechsleri P. lateralis P. megasperma …many more P. parasitica P. syringae

P. nicotianaeP. ramorum

top diebacks, leaf spots, stem cankers

Phytophthora cinnamomi

infects 900 different species

Many Phytophthora species have a wide host range:

Phytophthora root rot

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Douglas-fir infected withPhytophthora spp.

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Photo: Jennifer Parke, Oregon State University

Phytophthora root rotAPS Digital Image Collection

Severe root rot

Phytophthora cinnamomi on Ilex glabra ‘Shamrock’

Top dieback

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Top diebackV-shaped dead areas

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Symptoms on camellia

Photos: Oregon Dept. of Agriculture & Cheryl Blomquist, CDFA

Symptoms on camellia

Photo: Cheryl Blomquist, CDFA

P. ramorum symptoms on Kalmia

Photo: DEFRA

Sun scorch

Gray spot on sun scorched leaves

Similar symptoms – not Phytophthora

Photo: Rich Regan, Oregon State University

Photo: Peter Angwin, USDA-Forest Service

Not Phytophthora

Cercospora on Kalmia

Bleedingcankers

beech

beech

Photo by Joseph O'BrienBugwood.org image collection

Reddish-brown discolorationcambium area infected with

Phytophthora spp.

Phytophthora cactorum

Phytophthora citricola

Phytophthora plurivora

Phytophthora on European beech (Fagus sylvatica)

Weiland, Nelson and Hudler. 2010Plant Disease 94: 1009-1014

Taxus

Coastal live oak infected withPhytophthora ramorum

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Phytophthora ramorum

Photos: Mike McWilliams, ODF & Bruce Moltzen, Missouri Dept. of Conservation

“bleeding”

Phytophthora ramorum

Sudden …usually slow

Oak …many other suscepts

Death …often not lethal

African violet infected with Phytophthora spp.

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Penn State image collection

Hosta infected withPhytophthora spp.

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Lavender infectedwith

Phytophthora spp.

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Polemonium infected with

Phytophthora spp.

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Catharanthus = annual vincainfected with

Phytophthora spp.

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Phytophthora nicotianae on petunia

Phytophthoradetection

Phytophthora species in general:Antibody test (ELISA)Semi-selective media

Specific Phytophthora(P. ramorum)

Nested PCR DNA test

ELISA

Plating

PCR

Photo: Natalie Goldberg, New Mexico State University

Phytophthora detection

Baiting:

If you collect a sample Collect various stages

of symptoms.

Photo symptoms and environment.

Packaging a sample DRY paper towel Double bag and seal Crush proof box Sample submission form

outside of bags

Overnight express Monday-Thursday

Phytophthora ramorum

Photo: UC Davis & UC Berkeley

Phytophthora ramorum in culture

Chlamydospores

Sporangia releasing zoospores

QUESTIONS???