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Plant Resistance To Pests > Weeds- Mid Term > Flashcards

Weeds- Mid Term Flashcards

1
Q

Pest -def

A

An organism detrimental to humans or human concerns

generally insects, weeds, pathogens

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2
Q

Parasitc weeds are directly

A

dependant on the host

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3
Q

We want the host plant to be ___ to herbicides

A

resistant

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4
Q

When was chemical weed controlled developed

A

WW2 commercialized in 1950s

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5
Q

Major Herbicide Classifications based on Physiology

A
  1. Inhibition of photosynthesis
  2. Inhibition of plant growth
  3. Inhibition of Biosynthetic processes (amino acid synthesis, lipid synth)
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6
Q

Mechanism of Action (def)

A

The precise biochemical (inhibition of sp. enzyme) or biophysical (inhibition of electron flow) reaction or series of reactions that create a herbicides final or ultimate effect

(site of action, specific target of an herbicide)

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7
Q

Mode of Action (def)

A

The sequence of events that occur from herbicides first contact with a plant until its final effect (often plant death) is expressed.

(All events from application to death)

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8
Q

Ways that herbicide resistant crops are developed

A
  1. naturally tolerant
  2. Developed using tradition breeding methods
  3. Mutagensis
    D. Genetic Engineering (majority)
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9
Q

Ways that Herbicide resistant weeds happen

A

Naturally evolved

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10
Q

Resistant Crop (to herbicide def)

A

The inherited ability of a crop to survive and reproduce following exposure to a dose of herbicide normally lethal to the original crop

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11
Q

Stacked resistance (crops to herbicides)

A

Crop that is resistant to 2+ herbicides

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12
Q

Herbicide resistance

Why do weed control failures not necessarily mean herbicide resistance?

A
  • improper dosage
  • lack of coverage
  • stage of weed growth at application
  • climactic conditions
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13
Q

Herbicide Resistance in Weeds definition

A

The Inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide that was previously known to control the population

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14
Q

How does herbicide resistance develop in weeds

A

A change in the population over time where resistance individuals survive and reproduce and begin to dominate the population

There is naturally extensive genetic variation in weeds that allows for this possibility. Crops only have one genotype.

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15
Q

population

A

A field of not controlled palmer

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16
Q

Herbicide Tolerance -definition

A

The inherent ability of a species to survive and reproduce after use of a dose of herbicide that controls a susceptible species.

Implies no selection or genetic manipulation. Naturally tolerant. Has never been controlled by that herbicide

No change in population over time

17
Q

Why do herbicide resistant weeds evolve (from a management perspective)

A

Extensive/repeated use of herbicides

continuous threat to weed management

fewer herbicide options and increased costs

18
Q

Cross resistance (herbicide resistance in weeds)

A

Resistance to two or more classes of herbicides in the same group acting on the same target site.

Resistance to two or more groups of herbicides dues to a single common mechanism of resistance.

19
Q

When changing herbicides we need make sure the ___ changes as well

A

mechanism

20
Q

Why would single herbicide resistance be preferred by growers?

A

It’s easier to find other herbicides that work.

21
Q

Single Resistance (to herbicides in weeds)

A

Resistant to only one herbicide

22
Q

Multiple Resistance (to herbicides in weeds)

A

Resistant to two or more herbicides with different target sites or mechanisms

Resistant by multiple mechanism

23
Q

Why might a weed sp. develop multiple resistance to herbicides?

A

Continuous applications of a single herbicide of MOA, and selection for HR biotypes, followed by repeated applications of another herbicide and selection for biotypes.

24
Q

Low-level resistance visual scoring

A

Plant response from slightly injured to nearly dead

majority of plants display immediate response

25
Q

High-level resistance visual scoring

A

Plants are slightly injured or uninjured
Few plants have an intermediate response
-plants look untouched even at a high dose

26
Q

Herbicide Tolerance in crops is based on ___ principle

A

selectivity

27
Q

Herbicide Resistance in crops is based on

A

Genetic manipulation

28
Q

Selective Herbicide definiton

A

Herbicide that kills or significantly retards growth of weed without significantly damaging the crop

29
Q

Herbicide Metabolism def

A

Breakdown of herbicides into non-toxic compounds

-refers to a change in the chemical structure of the herbicide molecule. A minor change can drastically change the herb. activity

30
Q

Phases of herbicide metabolism

A
  1. oxidation, reduction, and hydrolosis
  2. Conjugation reaction to limit mobility and stop herb. metabolic activity
  3. Form secondary conjugates, is non-toxic and can be move elsewhere
31
Q

Factors influencing herb metabolism rate

A
  • plant is under environmental stress = less efficient
  • Excessive herb. rates (misapplication) can reduce plants ability to metabolize herb.
  • Other pesticides, chemicals (competition for enzymes, or inhibition of enzymes by insecticides)
32
Q

Altered Target Site - Resistant Crop Enabled

-how is it done

A

The target site is insensitve to herbicides

Ge based- INsertion of insensitive target gene via genetic engineering

Conventional breeding- insertion of insensitive target from wild species.

33
Q

Negative Cross Resistance (weeds to herbicides)

A

Resistant to one MOA of herbicide by highly susceptible to the other MOA of herbicides

34
Q

How to confirm herbicide resistance in a weed

A
  1. Full analysis of application
  2. Past experience (has this happened nearby or elsewhere)
  3. Seed collection from the resistant population and a nearby susceptible population
  4. Greenhouse dosage studies
  5. Must show the trait is heritable
35
Q

GR50

A

Amount of herbicide required to reduce the plant population by 50%

36
Q

NTSR Mechanism in weeds

Non-Target Site Resistance

A
  1. Altered herbicide absorption, translocation, or sequestration
  2. Enhance metabolism/detoxification (most common)
37
Q

TSR Mechanisms in weeds

Target Site Resistance

A
  1. Mutations in the target gene
  2. Target gene amplification (allows plant to continue to function normally)
  3. Over-expression of target gene/enzyme
38
Q

Implications of NTSR in weed management

A
  • Many genes are involved
  • slow to develop
  • cross resistance
  • Weeds may have evolved resistance to unknown herbicides
39
Q

Implications of TSR in weed management

A
  • Major genes involved
  • Develops quickly
  • Generally high level of resistance
  • Resistance spreads rapidly

Plant Resistance To Pests (6 decks)

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