Phytophthora

Question 1

Phytophthora ramorum - general notes

Answer 1

Fungus-like organisms closely related to those causing potato blight, root rot and bleeding canker.

Associated with sudden oak death, affects woody hosts including Rhododendron and Viburnum

Recent introduction from USA.

Question 2

Phytophthora ramorum and kernoviae - symptoms

Answer 2

Brown spreading lesions on leaves - often starting at petiole, leaf margin or tip.
Lesions often progresses more rapidly down main vein giving v shaped appearance.
Internal tissues below lesions are brown.
Wilting and dieback often result.
On trees patches of dead bark may occur with decay underneath.
Trees such as Fraxinus only have symptoms on leaves.

Question 3

Phytophthora ramorum and P. kemoviae - spread.

Answer 3

Favour wet and humid conditions.
Spores produced on leaf lesions on hosts are splashed around around to create new infections on the shrub leaves bark infections in vicinity.
Long-lived resting structures contaminated soil.
Can be transported on wheels, boots and animal feet.
May be transported by water (found in rivers near outbreak sites).
Most outbreaks caused by transportation of affected plant material.

Question 4

Phytophthora ramorum and P.kemoviae - lifecycle

• are produced on surface of - and - -.

Answer 4

Sporangia are produced on surface of leaf and twig blights.

Question 5

Phytophthora kernoviae - general notes.

Answer 5

New pathogen to SW of UK also in New Zealand (2008)
Similar symptoms to Phytophthora ramorum - lesions on leaves and leaf death. Black lesions on bark.
Range of hosts, seems more aggressive to rhododendron.
Not much known about lifecycle, swimming Zoospores released during sporulation.
Production of chlamydospores is not confirmed.
Notifiable in the UK.

Question 6

Phytophthora lifecycle

- dispersed by - splash and - currents and in - and - and moved debris.

Answer 6

Sporangia dispersed by rain splash and wind currents and in streams and rivers and moved debris.

Question 7

• are produced from the - upon contact with a suitable - species, penetrate the - tissue and initiate - -

Answer 7

Zoospores are produced from the sporangia upon contact with a suitable host species, penetrate the host tissue and initiate new infection.

Question 8

• spread by -.

Answer 8

Infection spread by hyphae.

Question 9

• • survive in soil for long periods of time, - produced when conditions are favorable.

Answer 9

Asexual chlamydospores survive in soil for long periods of time, mycelium produced when conditions are favourable.

Question 10

• • (A1 & A2) required for sexual reproduction by -.

Answer 10

Mating types (A1 & A2) required for sexual reproduction by oospores.