Plant Pathogens

Question 1

What are biotrophic pathogens?

Answer 1

Pathogens that need the host to be alive to gain nutrients.

Question 2

What are Hemibiotrophic pathogens?

Answer 2

Pathogens begin as biotrophic and later switch to a necrotrophic lifestyle.

Question 3

What are necrotrophic pathogens?

Answer 3

Pathogens that kill cells before colonising by secreting toxins.

Question 4

What are the different ways diseases spread?

Answer 4

Air-borne
Soil-borne
Seed-borne
Vector transmission (fungi, nematodes ect.)
Mechanical contact

Question 5

What are the features of fungi?

Answer 5

Hyphae; Branched filaments called mycelia

Spores; either on tips of hyphae (conidia) or in a sac (sporangiospores).

Question 6

How do fungi grow?

Answer 6

Via budding or binary fission with the ability to switch between the hyphal and yeast phase (dimorphism)

Question 7

What are the stages of pathogenic infection?

Answer 7

Penetration
Infection
Colonisation or sporulation
Spread

Question 8

Name a major pathogen to wheat.

Answer 8

Pycnidia; Hemibiotrophic fungi causing Septoria.

Question 9

What are the methods for controlling STB?

Answer 9

Monitor crops for early symptoms
Weather forecast-septoria timer
Fungicide control

Question 10

How many genes are resistant to STB?

Answer 10

22 e.g STB6

Question 11

Name a pathogenic Oomycete

Answer 11

Phytophthora infestans
(potato blight)

Question 12

What is the worldwide loss by blight?

Answer 12

$5 billion annually

Question 13

When were potatoes brought to Europe?

Answer 13

The 16th Century from South America

Question 14

When was Phytophtora infestans observed in Europe?

Answer 14

The 19th Century

Question 15

How much is the cost for fungicide application in Ireland for blight?

Answer 15

5 million euro

Question 16

What control methods are used for late blight?

Answer 16

Monitoring for early symptoms.
Weather forecast
fungicide

Question 17

What genes are resistant to blight?

Answer 17

11R genes from Solanum demissum

Question 18

What is the ideal temperature for blight spread?

Answer 18

temperatures above 10C and humidity above 95%

Question 19

What sort of pathogen is a virus?

Answer 19

A biotrophic pathogen

Question 20

Are viruses alive?

Answer 20

No, they can’t maintain homeostasis, respond to stimuli, or carry out metabolism.

Question 21

How do aphids spread plant viruses?

Answer 21

They ingest virions while feeding on phloem sap and transmit them when feeding on other plants.

Question 22

Name a potato virus.

Answer 22

Potato Virus Y (PVY), a virus that affects the Solanaceae family.

Question 23

How is PVY transmitted?

Answer 23

By the aphid Myzus persicae.

Question 24

What is a control method for PVY?

Answer 24

Resistance breeding using genes from Solanum stoloniferum.

Question 25

What are the features of a virus?

Answer 25

Simple: proteins encapsulated by genetic material. Host cell: virus cant replicate without hos cell. Spread: through vectors or machinery.

Question 26

What causes brown rot in potatoes?

Answer 26

The bacterium Ralstonia solanacearum.

Question 27

What type of pathogen is Ralstonia solanacearum?

Answer 27

A necrotrophic bacterial pathogen.

Question 28

How is Brown rot regulated?

Answer 28

It's a quarantine disease under the EC Plant Health Directive

Question 29

How can Ralstonia solanacearum spread?

Answer 29

Through infected roots of S. dulcamara in watercourses used for irrigation.

Question 30

What is the life cycle of Brown rot?

Answer 30

Begin as saprophytic (survives on soil organic matter. then pathogenic (feeds on live host).

Question 31

What does Brown rot do?

Answer 31

Blocks plant's vascular system. Degrades cell wall. Releases nutrients for bacterial growth.

Question 32

What structure do nematodes use to feed on a plant?

Answer 32

A stylet

Question 33

What sort of pathogens are nematodes?

Answer 33

Obligate biotrophs.

Question 34

What is the global economic impact of plant parasitic nematodes?

Answer 34

Over $100 billion in crop losses annually.

Question 35

Name a nematode

Answer 35

Potato cyst nematode

Question 36

What symptoms do PCN induce?

Answer 36

Thickening of roots Delay in tuber initiation Spread of tuber sizes

Question 37

How long can PCN persist in the soil?

Answer 37

20–30 years.

Question 38

What cultural methods control PCN?

Answer 38

Crop rotation, eliminating volunteer potatoes, and using cover crops.

Question 39

What is the PCN Directive?

Answer 39

Test all seed potato land annually Test 1% of ware potato land annually