Pathology L2 Viruses

Question 1

How are classes of biotic stress categorized

Answer 1

Size
Phylogenetic context
Levels of biological complexity
Importance as casual agents

Question 2

________ of infectious disease in plants are caused by viruses

Answer 2

Around 50%

Question 3

Tulipomania

Answer 3

First known financial bubble causes by a virus that made a marbled tulip

Question 4

Kochs Postulates

Answer 4

1. Must be found in diseased but not healthy organisms
2. Must be extracted and isolated from the diseased organism and grown in culture
3. Must cause disease when introduced to a healthy plant
4. The re-isolated organism from the inoculated plant must be same as original

Question 5

Who worked on the mosaic disease of tobacco

Answer 5

Mayer, Ivanovski, and Beijerunck

Question 6

What did Mayer find about mosaic disease of tobacco plants

Answer 6

Could not produce and culture or find the reason for disease under a microscope

Question 7

What did Ivanovski show about the mosaic disease of tobacco

Answer 7

Showed the filterability of the causal agent with a chamberland filter

Question 8

What did Beijerinck suggest about the mosaic disease of tobacco

Answer 8

Suggested presence of non-cellular organism (virus)

Question 9

Virus

Answer 9

Obligatory cellular parasites with minimal genetic info that utilize host cell resources for translocation, replication and assembly

Question 10

Viruses have a ______________ genome consisting of DNA or RNA

Answer 10

Very small

Question 11

How are viruses classified

Answer 11

Baltimore scheme

Question 12

T or F: RNA viruses are more common in plants

Answer 12

T

Question 13

2 parts of virus structure

Answer 13

Capsid (protein shell)
A nucleic acid genome

Question 14

2 forms of capsids

Answer 14

Helical - rod or filaments
Spherical- icoshedral

Question 15

Viroids

Answer 15

Infectious piece of RNA that doe not have a protein coat or produce proteins

Question 16

How do viruses cause disease

Answer 16

Using plant cellular substances during multiplication
Taking up spc3 and disrupting cellular processes
Upsetting metabolism and cell function

Question 17

Viral disease symptoms

Answer 17

Necrotic spot/ring
Mosaic yellowing
Stunted growth

Question 18

What can chlorosis be caused by

Answer 18

Nutrient deficiency
Herbicide drift
Virus infection

Question 19

Types of transmission of viruses

Answer 19

Seed transmission
Mechanical transmission
Vegetative propagation and grafting
Vectors

Question 20

Seed transmission

Answer 20

Use of seed derived from an infected plant

Question 21

Mechanical transmission

Answer 21

Contact between infected and healthy leaves (wind, shears, knives)

Question 22

Vegetative propagation and grafting

Answer 22

Placing infected plant parts with healthy plants

Question 23

Most common disease vector

Answer 23

Insects

Question 24

How does the triangle change in viruses

Answer 24

Environment in replaced with vector

Question 25

Strategies of virus disease management

Answer 25

Resistance variety Virus-free materials Sanitary measures Vector control Scouting/early detection and removal of infected plants

Question 26

Example of virus resistant varieties

Answer 26

Peas. En gene=resistance to pea enation mosaic virus. Mo gene=resistance to bean yellow mosaic virus

Question 27

Why is it so hard to identify viruses

Answer 27

No visual sign Symptoms can be confused with other factors Viruses cannot be seen or cultured

Question 28

How to detect viruses

Answer 28

Must be done with molecular tests with either commercial ones or plant matter sent to a lab

Question 29

Steps and approaches of virus control

Answer 29

Field scouting Seed selection/resistance variety Crop rotation Remove weeds Manage insect vectors

Question 30

Tobacco mosaic virus

Answer 30

Family - vigraviridae Genus - tobamovirus First described virus, transmitted mechanically

Question 31

Pepper mild mottle virus

Answer 31

Family- virgraviridae Genus - tobamovirus Positive sense RNA virus

Question 32

Wheat streak mosaic virus

Answer 32

Family - potyviridae Genus - tritimovirus Transmitted by wheat curl mite and infects wheat, barley, oat, corn, and rye

Question 33

Pea seedborne mosaic virus

Answer 33

Family - potyviridae Genus - potyvirus Transmitted by pea aphid or infected seed and affects pea, lentil and faba bean

Question 34

Potato virus Y

Answer 34

Family - potyviridae Genus - potyvirus Transmitted by aphids, mostly in Alberta

Question 35

Bean leaf curl virus

Answer 35

Family - tombusviridae Genus - luteovirus On pea and chickpea leaves found in Saskatchewan