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Insects, Microbes, Plants > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What are some examples of important plant fixed physical defenses?

A

Lignin, Cuticle, Trichomes

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2
Q

How might trichomes provide defense?

A

Trap and impale an insect

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3
Q

What is a phytoanticipan?

A

– Plant secondary metabolites with anti-microbial or anti-herbivore properties
– Formed before pest/pathogen attack!
– 4 Main Classes:
Phenolic Compounds, Saponins, Alkaloids, Terpenoids

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4
Q

What is the functional role of nicotine for plants that produce it?

A

Blocks insect’s acetylcholine receptors (overstimulation, paralysis and death)

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5
Q

How do some insects/pathogens overcome or even exploit these fixed chemical defenses?

A

Some insects are immune to the toxins, so they consume them and then use them in their bodies to deter their own predators

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6
Q

What are some examples of induced structural defenses?

A

Cork layers, Callose Papillae, Abscission Layers

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7
Q

How is a phytoalexin different than a phytoanticipan?

A

Phytoalexins are Produced in response to non-specific pathogen/insect signals
or wounding

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8
Q

What is the hypersensitive response and what pathogens is it useful against?

A

Triggered by specific gene for gene interaction, Causes localized death of plant cell(s) and production of antimicrobial compounds. Useful against BIOTROPHIC pathogens. Retreats but destroys everything useful to (biotrophic) enemy

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9
Q

What are some potential triggers of systemic acquired resistance?

A

Being exposed to pathogens or artificial chemical stimuli

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10
Q

why isn’t systemic acquired resistance activated all the time?

A

It needs an initial infection

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11
Q

What is a biological control?

A

use of natural enemies to suppress pest populations

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12
Q

What are main types of natural enemies for insects, and what are the differences between them?

A

Pathogens: organisms that cause disease to another
Predators: animals that consume other living things
Parasitoids: an insect that spends its larval stage in or another organism (aka host)

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13
Q

What are the 4 kinds of applied biological control we discussed?

A

classical, augmentative, neo-classical, conservation

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14
Q

Classical bio control definition and pros and cons

A

Classical: Introduction of new natural enemies (establishing permanent pop.)
PRO: Can be very effective (long-term)
CON: Dealing with non-native species risks invasion

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15
Q

Augmentative bio control definition and pros and cons:

A

Augmentative: Periodic release of natural enemies (establishment is not the goal) - VERY successful is greenhouses, mixed results in the field
PRO: Dealing with natural enemies that are already present-reduced risk of non-target or subsequent invasions
CON: Fighting against the ecological pressures that are already in place to keep natural enemy populations low: difficult to know how many individuals to release or if they will have an effect

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16
Q

Neo-Classical bio control definition and pros and cons

A

Neo-classical: Target native pest with non-native species - MOST SUCCESSFUL
PRO: Totally new associations will be more devastating to pests because the pest has not coevolved with its enemies
CON: Over time, coevolution will theoretically dampen this effect

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17
Q

Conservation bio control definition and pros and cons

A

Conservation: Using management practices to increase or enhance control by natural enemies already in the environment
PRO: can provide temporary diversity to support beneficials throughout the season
CON: can accidentally outbalance the predator / prey

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18
Q

Define the inoculative versus inundative releases (both augmentative) and when they might be used.

A

Inoculative: release fewer individuals and expect population growth via reproduction (i.e., several generations across the season) (use when you want the predator around a little longer)
Inundative: release millions on individuals (no reproduction expected), just one generation of targeting the pest (use when you don’t want the predator sticking around as long)

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19
Q

Generalists versus specialists and the differences between an organism’s physiological range and ecological range

A

Generalists: predators that target many species
Specialists: predators that target a specific species
Physiological range: all potential hosts that can be consumed and support growth and reproduction
Ecological range: hosts that are actually consumed in natural ecosystems
EX: It is physiologically possible for B. communis to use A. monardae as a host, but ecologically improbable cause of where they are

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20
Q

Define what GMOs are (not just what GMO stands for).

A

An organism whose genome has been altered in a specific way by genetic engineering
EX: a tomato expressing a gene from fish OR
corn that produces! dsRNAs targeting corn rootworm

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21
Q

Understand the differences between genomes, chromosomes, and genes.

A

Genome: the language cells pass to offspring
Chromosome: a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes
Gene: a distinct sequence of nucleotides forming part of a chromosome

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22
Q

Understand the differences between genetic changes created through selective breeding and genetic modification.

A

Selective breeding: choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics
Genetic modification: transferring a piece of DNA from one organism to a different organism

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23
Q

Understand the different types of traits found in different GMO varieties

A

EX: non-browning in food,
insect resistance in corn for ethanol or livestock feed,
herbicide tolerance

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24
Q

Understand the importance and utility of new tools such as RNAi and CRISPR

A

RNAi reduces gene expression at the mRNA level (knockdown), while CRISPR completely and permanently silences the gene at the DNA level (knockout)

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25
Q

Understand how GMOs are created (generally).

A

“Cut and stitch method” - DNA fragments are cut and combined in sections

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26
Q

What are the three dimensions of plant diversity and how can they be used to control insect pests?

A

Temporal: Primarily impacts pest diversity, abundance, and persistence
Spatial:
Smaller scale: within a field, different plots or rows
* Trap plants: attract pests away from main crop
* Push-pull : one crop deters pests, while the other attracts them
* Banker plants- provide resources for natural enemies
Larger scale: between fields, landscapes = less control and stronger effects on mobile species
Plant genotypes/phenotypes: Traits that encourage natural enemies

27
Q

What is a trap crop? The push-pull system? A polyculture?

A

Trap crop: attract pests away from main crop
Push-pull system: one crop deters pests, while the other attracts them
Polyculture (intercropping): the planting of multiple plant species or varieties to garner ecological benefits that make the habitat less suitable for pests

28
Q

What is the resource concentration hypothesis and the enemies hypothesis and how does each affect insect pests?

A

Resource concentration hypothesis: Predators and parasites are more effective at controlling herbivore populations in diverse habitats or plant communities because, diverse plant communities support a diversity of herbivores. Provides steady stream of prey for predators
Enemies hypothesis: Less diverse plant communities support less diverse insect communities, which limit the abundance of natural enemies

29
Q

What role do chemical signals play in pest damage?

A

can prevent specialists from finding host plants

30
Q

Understand the differences between genotype and phenotype.

A

Genotype: genetic characteristics
Phenotype: emergent or functional characteristics
(Genotype leads to phenotype)

31
Q

What is the definition of resistance?

A

a heritable decrease in the susceptibility of a pest to a pesticide

32
Q

Understand and contrast the different mechanisms through which insects can become resistant (e.g. target site, behavioral, physiological)

A

Target site: Bt Cry proteins bind to specific proteins in the insect gut -> insects evolved to have different shapes of these proteins in their gut so Cry can not bind
Behavioral: Avoidance of the control method.
EX: cockroach borax poison baited with sugar to get the roaches to eat the poison -> roaches evolved to avoid glucose.
Physiological resistance: the ability of an insect population to survive exposure to a concentration of insecticide that would normally result in complete kill

33
Q

How do pests evolve resistance to insecticides, i.e., what are the necessary steps?

A
  1. Genetic variation/phenotypic variation
  2. Differential survival
  3. Inheritance
    (repeat)
34
Q

What circumstances promote resistance? How can it mitigate the evolution of resistance?

A
  • Tactics that have strong impacts on survival impose stronger
    selection
  • High resistance allele frequencies prior to selection
  • Low cost of carrying resistance alleles
  • When resistant alleles are dominant
  • Monogenic resistance phenotypes
  • When pests have short generation times and high fecundity
35
Q

What are the assumptions of the high dose/ refuge strategy for resistance management? Are they likely met?

A

Assumption #1: resistance is recessive
Assumption #2: resistance alleles are rare (<0.1%)
Assumption #3: mating is random within fields and occurs across fields
(not likely met)

36
Q

What is a vector?

A

The sucking insects that spread mostly viral and cell-wall-less bacterial pathogens

37
Q

Understand the co-evolutionary dynamic that occurs between plant pathogenic microbes and their insect vectors.

A

Ex: A bug with a long sucker antenna infects a deep flower, so the flower gets deeper and the insect’s antennae get longer and they go back in forth with this for generations

38
Q

Compare and contrast the characteristics of a persistent and a non-persistent vector

A

Persistent vector
– Virus must circulate or propagate through insect to be re-injected
– Several hours required before virus can be transmitted after feeding (latent period)
– Insect retains virus for days/weeks (Some can even pass to offspring!)
Non-persistent Vectors
– Often stylet borne
– Pathogen acquired quickly by vector
– Can be passed to new host immediately
– Vector loses ability to transmit pathogen within minutes

39
Q

Understand how a pathogen benefits from influencing vector behavior and how that can differ depending on if it is a persistent vs. a non-persistent vector.

A
  • Pathogens with persistent vectors helped those vectors at all stages
  • Pathogens with non-persistent vectors attract vectors to infected plant but don’t want them to stay long (pull-push strategy)
40
Q

Know the strict definition of a biocontrol agent of pathogens

A

Use of living organisms to control pests or pathogens

41
Q

What are some examples of biocontrol agents and what are examples of their modes of action?

A

Bacteria: Competition (multiple)
Fungi: Hyper-parasitism, induction of plant defenses, antagonism
Pathogens: Reduction of Plant Abiotic Stress

42
Q

What are some pros and cons of biocontrol of plant pathogens compared to chemical sprays?

A

PROS:
Less toxic
Pest resistance development is rare
Consumer acceptance
CONS:
Harder to understand how they work (and why they can fail to work)
Living = lower shelf life
Tend to be more specific to plant/pathogen

43
Q

Know the definition of a “suppressive soil” and some ways that they have formed.

A

Disease Suppressive Soils: Soils which have an innate ability to suppress soil-borne plant disease
Formed by
“Take-all decline”: Soil develops suppressive characteristics as bacteria builds in the soil and disease then decreases
Composts
Increase microbial mass

44
Q

Why might long term monoculture be good in some very specific situations?

A

It can (rarely) lead to take-all decline which is when soil develops suppressive characteristics as bacteria builds in the soil and disease decreases

45
Q

Know how the use of compost potentially relates to disease suppression

A

– Many pathogens killed by heat in composting process
– Saprophytes tolerate it more effectively
– Also plant benefits from nutrients and water retention

46
Q

How can diversity of crops through time be used to manage pathogens?

A

Reduction of soil and residue borne pathogens

47
Q

How can diversity of crops through time be used to prevent the loss of plant resistance?

A

Leads to more non-hosts plants

48
Q

What is the difference between intercropping and multiline?

A

Intercropping: Mixtures of different crop species
Multiline: Mixtures within crop species

49
Q

What are some potential mechanisms of how intercropping lowers disease pressure?

A

– Replacement Type
– Addition Type

50
Q

Which pathogen types have resistance issues and which do not

A
  • Fungi
    Fungicides (resistance issues exist)
  • Bacteria
    Antibiotics and copper (resistance issues exist)
  • Nematodes
    Nematicides (no documented field resistance)
  • Viruses
    No direct chemical controls available!
51
Q

The difference between discrete vs. stepwise resistance patterns

A

discrete = 2 peaks on grapgh (often “no” fitness cost)
stepwise = several in concession (some fitness cost)

52
Q

Mechanisms of resistance

A
  1. Alteration of target site
  2. Overexpression of target protein
  3. Active efflux of fungicide
  4. Metabolic breakdown of fungicide
53
Q

Resistance management strategies

A
  • Practice Integrated Pest Management
  • Restrict Use
  • Apply Correct Rates
  • Rotate MOA
  • Use multi-site MOA
54
Q

What is the meaning of “cross-resistance”?

A

Cross-Resistance: pathogen that evolves resistance to one fungicide typically also becomes resistant to other fungicides with same mode of action

55
Q

What is the technical definition of an invasive species

A

1) a non-native (or alien) to the ecosystem under consideration and
2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

56
Q

What are the ecological/evolutionary theories that attempt to explain what makes different types of organisms (plants, pathogenic microbes, insect herbivores) successful invasive species?

A
  • Lack of predators
  • Outcompete native species for food
  • Lack of co-evolutionary history
57
Q

What are the basic benefits to the plant provided by rhizobia (BNF, biological nitrogen fixation)?

A

Little nitrogen fertilization needed to grow legumes
Rhizobia add nitrogen to soil for next crop (Nitrogen Credit)

58
Q

What are the pros and cons of using rhizobia vs conventional fertilization?

A

PROS: Less runoff problems with rhizobia
CONS: Rhizobia more affected by soil conditions

59
Q

How do mycorrhizae benefit the plants they associate with?

A

– Provide micronutrients (P especially) and water to plant
– Also help defend against pathogens
– Plant provides fixed carbon (food)

60
Q

How do conventional agricultural practices affect natural mycorrhizal colonization?

A

Soil Nutrients?
– Phosphate (P) addition to plant can reduce mycorrhizal colonization
Tillage?
– Generally bad for mycorrhizae
Pesticide?
– Fungicides inhibit mycorrhizae
Cover Crops?
– Fallow periods and winter can reduce mycorrhizal inoculum by 30-40%
– Using mycorrhizal compatible cover crops in no-till systems can maintain viability

61
Q

What are the pros and cons of using plant resistance to manage plant disease compared to other management techniques?

A

PRO:
- Easy!
- Environmentally Friendly
- Cost Effective (if disease is present)
CON:
* May not be available!
* May not be highest yielding variety
* May not be as resistant to other pests/pathogens
* Less Flexible
* Must know potential problems before planting
* May fail over time!

62
Q

Compare horizontal and vertical resistance

A

Horizontal:
* Resistance is typically relatively durable!
* Hard to breed for!
Vertical:
* Resistance is relatively unstable!
* Relatively easy to breed for!

63
Q

What types of plant defenses tend to be most “durable” in the long term?

A

– The more specific the mode of action, the less durable the resistance

64
Q

What types of plant defenses might you not want in a crop?

A

Fixed, Horizontal

Insects, Microbes, Plants (2 decks)

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