PLP

Question 1

What is the term for the series of events leading to the development of an infectious disease?

Answer 1

The term is “Pathogenesis” or “disease cycle.”

Question 2

What does the disease cycle primarily refer to?

Answer 2

The disease cycle refers to the appearance, development, and perpetuation of the disease as a function of the pathogen.

Question 3

What is the difference between a pathogen’s life cycle and the disease cycle?

Answer 3

The life cycle of a pathogen refers to its growth and development stages, while the disease cycle encompasses changes in both the plant and pathogen over time.

Question 4

What are the primary events in the disease cycle?

Answer 4

The primary events include inoculation, penetration, infection, colonization, growth and reproduction of the pathogen, dissemination, and survival of the pathogen in the absence of the host.

Question 5

What is inoculum in the context of plant pathogens?

Answer 5

Inoculum refers to the infective pathogen propagules that come in contact with the host.

Question 6

What are primary and secondary inoculum?

Answer 6

Primary inoculum survives dormant and causes original infections, while secondary inoculum is produced from primary infections and causes subsequent infections.

Question 7

What determines the success of infection by a pathogen?

Answer 7

The success is determined by the amount of inoculum, environmental conditions, and the susceptibility of the host.

Question 8

What process attracts some types of inoculum in the soil to host plants?

Answer 8

The process is called chemotaxis, where chemical substances from plant roots attract pathogens like zoospores and nematodes.

Question 9

How do most pathogens attach to host surfaces before penetration?

Answer 9

Pathogens attach through adhesive materials like water-insoluble polysaccharides, glycoproteins, lipids, and fibrillar materials that become sticky when moistened.

Question 10

What is direct penetration in plant pathogens?

Answer 10

Direct penetration occurs when pathogens penetrate intact plant surfaces, commonly done by fungi, oomycetes, and nematodes.

Question 11

How do nematodes penetrate plant cells?

Answer 11

Nematodes penetrate by using repeated back-and-forth thrusts of their stylets to create an opening in the cell wall.

Question 12

What are natural openings through which pathogens can enter plants?

Answer 12

Natural openings include stomata, hydathodes, and lenticels.

Question 13

What is the incubation period in disease development?

Answer 13

The incubation period is the time interval between inoculation and the appearance of disease symptoms, varying from days to years.

Question 14

What happens during the infection process?

Answer 14

During infection, pathogens establish contact with susceptible cells, obtain nutrients, and may release substances that affect the host’s physiological processes, leading to symptoms.

Question 15

What are local infections?

Answer 15

Local infections involve a single cell, a few cells, or a small area of the plant, often remaining localized throughout the growing season.

Question 16

What are systemic infections?

Answer 16

Systemic infections spread rapidly and may involve large parts or the entire plant, often caused by fastidious bacteria, phytoplasma, and certain viruses.

Question 17

How do fungi and higher plants grow and reproduce within infected tissues?

Answer 17

Fungi and higher plants invade by growing on or into the tissues, continuing to spread within the infected host.

Question 18

How do bacteria reproduce within plant tissues?

Answer 18

Bacteria reproduce by fission, where one mature individual splits into two smaller individuals.

Question 19

How do viruses replicate inside host cells?

Answer 19

Viruses replicate by utilizing the cellular machinery of the host cells to produce more viral particles.

Question 20

What is the difference between the growth of fungi and the reproduction of bacteria and viruses?

Answer 20

Fungi grow and multiply within the host tissues, while bacteria, viruses, phytoplasmas, and viroids reproduce rapidly without significant increase in size, infecting new tissues in the process.

Question 21

What types of pathogens can penetrate through wounds?

Answer 21

Bacteria, most fungi, some viruses, and viroids can enter plants through various kinds of wounds.

Question 22

What is the role of haustoria in parasitic plants?

Answer 22

Haustoria are specialized feeding structures that penetrate host plant tissues to extract nutrients.

Question 23

What are the main forms of pathogen reproduction?

Answer 23

Fungi reproduce by spores, parasitic higher plants produce seeds, bacteria and phytoplasma reproduce by fission, and viruses and viroids replicate inside host cells

Question 24

What are the steps involved in the disease cycle?

Answer 24

The disease cycle involves the following steps:
1. Inoculation: Contact of inoculum with the host.
2. Penetration: Pathogen enters the plant.
3. Infection: Establishment of contact with host tissues.
4. Colonization: Pathogen grows and reproduces within the host.
5. Growth and Reproduction: Continuous growth and multiplication in tissues.
6. Dissemination: Spread of the pathogen to new hosts.
7. Survival: Pathogen survives in absence of the host (overwintering/over-summering).

Question 25

What is Integrated Disease Management (IDM)?

Answer 25

IDM is a disease management system that utilizes all suitable techniques and methods compatible with environmental and population dynamics to manage diseases below economically damaging levels.

Question 26

When did Integrated Disease Management gain focus, and why?

Answer 26

IDM gained focus in the 1960s due to environmental concerns regarding the overuse of chemicals like fungicides and insecticides, which caused pollution and health hazards.

Question 27

What methods does IDM emphasize for disease control?

Answer 27

IDM emphasizes cultural, biological, epidemiological, and alternative methods rather than solely relying on chemical control.

Question 28

What practices should be avoided in IDM?

Answer 28

Practices to avoid include indiscriminate use of fungicides, monoculture, and growing susceptible cultivars.

Question 29

Name the three different approaches of the Integrated Disease Management system.

Answer 29

1. Combined control approach 2. Surveillance-based approach 3. Advanced integrated disease management system.

Question 30

What is the combined control approach in IDM?

Answer 30

It combines control methods such as adjusting sowing time, seed treatment, use of resistant varieties, and chemical spray schedules.

Question 31

What is the surveillance-based approach in IDM?

Answer 31

This advanced approach is based on crop health monitoring and surveillance, taking into account economic threshold levels or economic damage levels.

Question 32

What does the advanced integrated disease management system involve?

Answer 32

It involves high input technology like computer-supported forecasting, remote sensing, scouting, and knowledge-based decision-making.

Question 33

What are the main components of integrated disease management?

Answer 33

1. Host resistance 2. Induced systemic resistance 3. Genetically improved plants 4. Cultural practices 5. Physical methods 6. Plant nutrition 7. Biological control 8. Use of plant-origin pesticides 9. Judicious use of chemicals.

Question 34

What is host resistance in IDM?

Answer 34

Host resistance refers to using resistant plant varieties as a practical, effective, and economical method of controlling plant diseases.

Question 35

What are the advantages of host plant resistance?

Answer 35

It has no adverse effect on the environment, involves no extra cost for farmers, and avoids the need for chemical applications.

Question 36

What are the disadvantages of host plant resistance?

Answer 36

Development of resistant varieties takes 5-10 years, may create selection pressure on pathogens, and can lead to new pathogen problems.

Question 37

How do plants respond to environmental stimuli?

Answer 37

Plants respond to stimuli like gravity, light, and nutrient availability, which can induce biochemical changes that enhance resistance to pathogens.

Question 38

What is systemic acquired resistance (SAR)?

Answer 38

SAR is a defense mechanism mediated by salicylic acid, leading to the expression of pathogenesis-related proteins that help resist infections.

Question 39

What role does potassium play in plant nutrition?

Answer 39

Potassium is crucial for plant survival under environmental stress and influences the plant’s reaction to pests and diseases.

Question 40

What is the significance of biocontrol agents in IDM?

Answer 40

Biocontrol agents suppress pathogen growth through antibiotic production, hyperparasitism, or competition, serving as environmentally friendly alternatives to fungicides.

Question 41

Give examples of biocontrol agents used in IDM.

Answer 41

Examples include Bacillus subtilis, Pseudomonas fluorescens, Trichoderma spp., and Agrobacterium radiobacter.

Question 42

What are pesticides of plant origin?

Answer 42

Pesticides derived from plant parts that possess antifungal properties, like garlic, which has medicinal and pesticidal uses.

Question 43

What is the judicious use of fungicides?

Answer 43

It refers to the rational use of fungicides to minimize environmental impact and avoid resistance development in pathogens while ensuring effective disease control.

Question 44

Describe the integration of cultural and chemical control.

Answer 44

This integration has resulted in improved disease management, exemplified by practices that reduce diseases in crops like watermelon and tomato.

Question 45

What is the integration of resistance, cultural, biological, and chemical control?

Answer 45

This comprehensive approach utilizes resistant cultivars, cultural practices, biocontrol agents, and pesticides to effectively manage diseases like club root in vegetables.