Plant disease development

Question 1

Define host.

Answer 1

It is an organism that provides nutrients for another organism.

Question 2

Define alternate host.

Answer 2

An alternate host is a different host plant from the primary host on which rust fungus can complete its life cycle.

Question 3

Define infection.

Answer 3

This is the process in which the parasite develops a parasitic relationship with the host.

Question 4

Define Pathogenesis.

Answer 4

This is the chain event that occurs during a disease’s development.

Question 5

What is Pathogenicity?

Answer 5

The ability of a pathogen to cause disease by interfering with one or more of the plant functions.

Question 6

What is inoculation?

Answer 6

This is the initial contact site of the pathogen where infection is possible on the plant.

Question 6

What is an inoculum?

Answer 6

Any part of the pathogen that can initiate infection. Ex: Fungal spores, bacterial cells, and virus particles.

Question 7

What are the 7 steps in the generalized disease cycle?

Answer 7

1. Attachment
2. Penetration
3. Infection
4. Colonization
5. Reproduction
6. Dissemination (spread)
7. Inoculation

Question 8

What are the two types of inoculation?

Answer 8

Primary and Secondary

Question 9

What is the difference between Primary and Secondary inoculation?

Answer 9

Primary: It is dormant during winter and active during spring. This causes the initial infection during the growing season.

Secondary: Produces on the host plant from primary infection to cause secondary infection.

Question 10

How is inoculum carried to the host?

Answer 10

By wind, water, soil, and insects.

Question 11

How do pathogens attach to the host?

Answer 11

Pathogens attach to the external surface of the plant by secreting an adhesive-like fluid that helps them adhere to the plant.

Question 12

What is incubation?

Answer 12

This is the time the pathogen spends on the host’s surface.

Question 13

What do fungi and bacteria do while incubating?

Answer 13

Bacteria: Start establishing a colony through Quorum sensing.
Fungi: Perceive the host surface for moisture and nutrients.

Question 14

What is Quorum Sensing?

Answer 14

Quorum sensing is when a single bacteria secretes signaling molecules called autoinducers to attract other bacteria in the same area of the plant. Once the bacteria reach virulence, it is then able to cause damage to the plant.

Question 15

What is Virulence?

Answer 15

It is a pathogen’s ability to cause damage to the plant.

Question 16

When do spores produce germ tubes?

Answer 16

During the incubation phase.

Question 17

What are germ tubes?

Answer 17

Germ tubes are specialized structures, different from mycelia and shorter in length.

Question 18

What are the three types of penetration?

Answer 18

Direct penetration, penetration through wounds, and penetration through natural openings.

Question 19

How can fungi penetrate?

Answer 19

They can penetrate through natural opening, direct penetration and through wounds.

Question 20

How can bacteria penetrate?

Answer 20

They can penetrate through wounds or natural openings.

Question 21

What is the difference between endoparasitic nematode and ectoparasitic nematode?

Answer 21

Ectoparasitic nematodes can not go inside of the root of the plant but Endoparasitic nematodes can.

Question 22

What is an Appressorum?

Answer 22

This is a part of the spore that secrets enzymes and penetrates through the plant cuticle using hydraulic pressure.

Question 23

What is the penetration peg?

Answer 23

This is a thin hypha pushed through the cuticle pressure created by appressorum.

Question 24

What is an infection?

Answer 24

An infection is when the pathogens reach the susceptible cells or tissue to extract nutrients.

Question 25

How do you know if the infection is successful?

Answer 25

It will result in the appearance of symptoms or signs.

Question 26

What are the steps of fungi invasion through colonization?

Answer 26

Symptoms start appearing. Spread from the point of inoculation. It invades the Xylem tissue and spreads through the Xylem sap.

Question 27

How do bacteria, viruses, and nematodes invade and infect new tissue?

Answer 27

By reproducing at a rapid rate. It is spread through Xylem, phloem, and plasmodesmata.

Question 28

How do fungi reproduce?

Answer 28

Spores

Question 29

How does bacteria reproduce?

Answer 29

Fission

Question 30

How does virus reproduce?

Answer 30

Replication.

Question 31

How does the dissemination of pathogens occur?

Answer 31

Contaminated seeds, Rain splash, Tools/Equipment, Animals, Insects, Water etc.

Question 32

How do pathogens survive?

Answer 32

On or in seeds, insects, parts of the plants, ex: roots.

Question 33

List 5 properties of pathogen that can lead to successful disease development.

Answer 33

1. Level of virulence.
2. Adaptability
3. Dispersal efficiency
4. Survival efficiency
5. Number of infective
   propagules available: spores, virus particles, bacteria cells.

Question 34

List 5 properties of a host that could lead to successful disease development.

Answer 34

1. Susceptibility
2. Growth stage and form.
3. Population density and structure.
4. Genetic uniformity of neighboring plants.
5. General health.

Question 35

List 4 properties of the environment that could lead to successful disease development.

Answer 35

1. Conditions that favor pathogens.
2. Conditions that promote plant growth or reduce resistance.
3. Conditions that affect dispersal.
4. Level of humidity, temperature, wind speed, and periods of rain.