Sudden Oak Death

Chlamydospores

Chlamydospores on and in bay leaf tissue (9 days after inoculation). Leaf tissue was cleared and stained to reveal chlamydospores, which appear blue in this photo.

Sporangia

Sporangia (both discharged and non-discharged), and immature chlamydospores from a bay leaf 48 hours after inoculation.

Sporangia & chlamydospores

Close-up of sporangia (football-shaped structures) and chlamydospores (larger, round, amber-colored structures), 7 days after inoculation of bay leaf disks. Note that some of the sporangia are empty, having already released zoospores.

Sporulation

Phytophthora ramorum sporulating on edge of bay leaf disk, 7 days after inoculation. Abundant sporangia and chlamydospores are present. Mature chlamydospores are amber-colored.

Sporangia

Sporangia on a bay leaf disk, 24 hours after inoculation. Zoospores are being released from the sporangia (the swimming zoospores appear as streaks in this photo).

Sporangia

Sporangia of Phytophthora ramorum on the edge of a bay leaf disk, 20 hours after inoculation.

Chlamydospore

High magnification of single Chlamydospore showing further lack of ornamentation. Chlamydospores: Spherical structures with little or no surface ornamentation and averaging 42µm in diameter.

Chlamydospore

Higher magnification of single chlamydospore to indicate further lack of surface ornamentation. Chlamydospores: Spherical structures with little or no surface ornamentation and averaging 42µm in diameter.

Chlamydospores

Chlamydospore surrounded by hyphae. Chlamydospores: Spherical structures with little or no surface ornamentation and averaging 42µm in diameter.

Chlamydospores

Chlamydospores; Note lack of surface ornamentation. Chlamydospores: Spherical structures with little or no surface ornamentation and averaging 42µm in diameter.

Chlamydospores

Chlamydospores, varied magnifications. Chlamydospores: Spherical structures with little or no surface ornamentation and averaging 42µm in diameter.

Cyst germination

Cyst germination

db_florence_zoosporangia_2b1

Hypahe in lenticels

Hyphae growing in lenticels

Hyphae

Hyphae - Note the nodular or nodose anatomy

Hyphae in xylem

Hyphae in the Xylem of the same stem as previous

Infected bay leaf

Lower surface of infected California bay leaf, Umbellularia californica. Note chlamydospore, zoosporangia, and hyphae.

Infected tanoak tissue

Infected tissue in tanoak (Lithocarpus densiflorus). Note the nodulated hyphae of Phytophthora ramorum.

Lenticel

Lenticel. Special structures in the periderm of the stem that allow for gas exchange. They are oval and average 37.67µm long by 20.2µm wide.

P. ramorum cyst

P. ramorum cyst. Cysts of P. ramorum average 5.5µm in diameter, spherical, display an undulating surface, and depending on the stage of development the closing longitudinal groove is observed as a pore.

P. ramorum cysts

P. ramorum cysts. Cysts of P. ramorum average 5.5µm in diameter, spherical, display an undulating surface, and depending on the stage of development the closing longitudinal groove is observed as a pore.

Tanoak cortex

Cortex in a 1 year old stem of tanoak (Lithocarpus densiflorus) infected with P. ramorum. Note: The thread like structures are the hyphae of P. ramorum

Zoosporangia

Zoosporangia prior to zoospore release; note pedicel (arrow).

Zoosporangia

Zoosporangia after release of zoospores. Note pedicel (arrow).

Zoospore release

Zoospore release

Zoospores

Zoospores from pure culture. Note the biflagellation, reniform shape, longitudinal groove, and pitted surface.

Zoospores

Zoospore from culture. Note the biflagellation, reniform shape, longitudinal groove, and pitted surface.

Zoospores

Zoospores from culture. Note the biflagellation, reniform shape, longitudinal groove, and pitted surface.