CFAN 2333 (Part 2)

Four Plant Physical Defense

Primary Cell Wall, Lignin Defense, Cuticle, Trichomes

Primary Wall Defense

cellulose, hemocellulose, pectin

Lignin Defense Strategy

grinds down insect mandibles, strengthen polymers in tissues, few microorganisms can breakdown

Cuticle Defense Strategy

deflects water, high wax content

trichome defense strategy

insect defense (impales), secrete antimicrobial properties, can reduce water loss

Three types of biological control

Classical, Augmentative, Conservation

Biocontrol

Using knowledge about biological interactions to facilitate control of pests, weeds and pathogens

Classical Biocontrol (planned invasion)

Targets non-native pests with one or more species from pest’s native range and attempts to incorporate a new (non-native) natural enemy in a new environment

Advantages of Classical Biocontrol

long term, no ongoing intervention requires

Neo-classical biocontrol

insect did evolve here, natural enemies are not controlling populations

Augmentative Biocontrol

Mass rearing and release of natural enemies to increase their local population size, establishment is not the goal, successful in greenhouse

Disadvantages of Classical Biocontrol

expensive, Invasion risk, off target effects,

Disadvantages of Augmentative Biocontrol

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

Advantages of Augmentative Biocontrol

Dealing with natural enemies that are already present-
reduced risk of non-target or subsequent invasions

Conservation Biocontrol

Using management practices to increase or enhance control
by natural enemies

Fixed Plant Defense

constitutive, always expressed

Induced Plant Defense

triggered by something

Types of Fixed Plant Defenses

Lignin, Cuticle, Trichomes

Four Classes of Phytoanticipants (Chemical Defense)

Phenolic Compounds, Saponins, Alkaloids, Terpenoids

Chemical defenses are

formed before pest/pathogen attack

Phenolic Compounds

Anti-microbial and herbivore properties

Types of Phenolic Compounds

Flavenoids, Lignan, Tannins

Alkaloids

Naturally occurring, N containing

Types of Alkaloids Used

Nicotine, Cocaine, Neonictionids (synthetic)

Botanical Insecticides

Neem oil, Rotenone

Essential Oil Pesticides

Clove, Mint, Rosemary, Thyme (Insect Repellent/Antagonists),

Pros of Plant Resistance instead of other control techniques

There is less reliance on chemical treatments and other management techniques (IPM) which in turn saves money and time

Cons of Plant Resistance instead of other control techniques

Specific cultivars may have the possibility of developing of susceptibility to non-target pest/pathogens of specific cultivars and costs associated with patented seeds.

Induced Defense Pros

Reacting to pest/pathogen targets allowing plasticity (temporary response)

Induced Defense Cons

Can cause stress to the plant and response has the potential to be triggered without the presence of pest/pathogen

Fixed Defense Cons

Difficulty with targeting specific plants/pathogens

Fixed Defense Pros

Always present therefore it does not have to be “prepared”

Pathogen/pest characteristics that might make resistance less durable

Pest/pathogen reproduction/life cycle, high population diversity among specific pathogen/pests, migratory habits among pests, modes of locomotion among pests

Parasetoids

Insects wounding a plant causes a plant response that parasitoid can sense, then they plant an egg inside/on the insect and develop inside until it's big enough to come out.

Four Biocontrol Agents used against arthropods

Predator, Parasoitoids, Pathogens, Nematodes

Protein Functions

Biochemical Reactions, Form Structures, Form Pathways between cells, Antibodies

GMO (Genetically Modified Organism)

An organism whose genome has been altered in a specific way through genetic engineering; insertion of a gene from a different strain or species (recombinant)

Paul Berg (1972)

first recombinant DNA molecules; SV40 and Lambda Virus

Herbet Boyer and Stanley Norman Cohen (1973)

First recombinant organism; E. coli with transgene for kanamycin resistant

Rudolf Jaenisch (1974)

first recombinant organism; mouse

French Research Group (1986)

first transgenic plants; tobacco w/ herbicide resistance

transgenic

contains genetic material into which DNA from an unrelated organism has been artificially introduced

Formation of New DNA into Cells/Organism

-Microinjection
-Virus or Bacteria
-Electroportation
- Natural Competence (Bacterial grab DNA from environment)

agrobacterium tumefaciens

the bacteria that produce crown gall disease in plants used to create GMOs (cut & stitch transformation)

CRISPR use in GMOs

Bacteria “save” small remnants of bacteriophage genomes by inserting them into their own genome

RNAi

involves production of and RNA molecule that specifically recognizes a target when it binds the resulting dsRNA is flagged for degradation

monoculture

the cultivation of a single crop variety

polyculture

growing more than one crop/variety in the same field at the same time

temporal (crop arrangment)

arrangement of crops in time (overlapping, rotation)

spatial (crop arrangement)

arrangement of crops within field or among fields

plant genotypes/phenotypes (arrangement)

arrangement of different genotypes and species

spatial plant diversity

trap plants, push-pull (one crop deters pest, one attracts), banker plants (provide natural resources for enemies)

temporal plant diversity

Simultaneous cropping, crop rotation, relay cropping (partial overlap)

Chemical interferences resistance

volatile compounds from polycultures can prevent specialists from finding host plants

genetic plant diversity

Same plant species, different genotype; Different plant species, distantly related

Resource Concentration Hypothesis

Herbivores are more likely to find and remain on hosts
growing in dense/pure stands

Enemies Hypothesis

Less diverse plant communities support less diverse insect communities, which limit the abundance of natural enemies

Top-down and bottom-up impacts

Diverse plant communities reduce herbivore abundance and increase natural enemy abundance, resulting in higher higher net herbivore control and lower herbivore damage to plants

Resistance

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

field-evolved resistance

functional resistance that exists in field populations

resistance failure

a sufficiently high frequency of resistance in a pest population so that economic damage occurs

tolerance (plant resistnace)

a reduction in susceptibility due to non-heritable factors

First year of documented plant resitance

1914

Year that resistance became widespread

1970s

Mechanisms of Resistance

Target Site-Resistance, Behavioral Resistance, Physiological Resistance

Target Site Resistance

proteins bind to specific proteins, evolved to have different shapes of these proteins cannot bind

Behavioral Resistance

avoidance of control method (ex. cockroaches and borax + sugar combo)

physiological resistance

metabolic resistance, penetration resistance, excreteion or sequestion resistance

metabolic resistance (physiological)

Changes in the organism’s physiology to breakdown the pesticide faster

penetration resistance (physiological)

Slower absorption via changes in the exoskeleton

sequestration/ excretion resistance (physiological)

Removal of the compound, or storage of the compound in a
location where it will not act on the target

Development of Resistance

due to selection; Differential survival and reproduction of individuals due to differences in phenotype

Factors promoting resistance

High resistance allele frequencies prior to selection, Low cost of carrying resistance alleles when resistant alleles are dominant

monogenic

of or relating to an inheritable character that is controlled by a single genes

Resistance Management Techniques

reduce selection pressure, create refuges for susceptible individuals, reduce using same more of action chemical, target complex traits that have high cost to new variants

IRM Tactics for GM Crops (Other)

pyramiding (multiple cry proteins in one crop), rotation (different cry proteins different years), RNAi corn (+/- Bt)

in vivo test

testing living cells ut outside usual natural conditions

in vitro test

living cells in actual natural condition

Biological Control Agent

Use of living organisms to control pests or pathogens

Potential Mechanisms of microbial BCAs

Hyperparatoidism, antagnims (prod. of microbial compounds), competition, induction of plant defenses
- reduction of anti-biotic stress

Pathogen Biocontrol Pros

low toxicity, EPA registration as "Microbial Biopesticides", Patent Protection , Sucessful use requires biological and ecological knowledge, Less associated w/ pest resistance development

Microbial Biocontrol vs Insect Biocontrol

terms such as classical, neoclassic, etc. don't apply, few success stories, failure is LESS risky

Phytoanticipant

Anti-Microbial Defense Compounds such as Saponin, Phenolic Compounds, Alkanoids, terpenoids

Function of Nicotine in Plants

blocks acetycholine recepters causing OVERSTIMULATION, PARALYSIS AND DEATH

How Insects overcome and exploit fixed chemical defenses

physical damage of plant, bioaccumulation of toxin

Phytoalexin

antimicrobial compounds that are always present or activiated

Hypersensitive Plant Response

Plant destroys anything useful causing localized death of plant cells

Four Natural Enemies for Insects

Parasitoids, Predators, Entomopathogenic Fungi, Nematodes, and viruses

Inundative release

release millions of individuals (no reproduction expected) just one generation targetting the pest

Inoculative release

release fewer individuals and expected populations growth through reproduction

Modes of Plant Diversity

Intercropping/multiline (space), Crop rotation (time; reduction of soil and residue borne pathogens), Relay cropping (overlap between rotations)

Worst Pathogen in Minnesota

Soybean Cyst Nematode

Natural Ecosystems are considered to have lower pathogen pressure than Agroecosystems because

More diversity therefore specific host density is lower

Intercropping

Mixtures of different crop species

Multiline

Mixtures within crop species

Why use multiline mixtures within crop species?

Many cultivars have varying resistance to different pathogen races

Pathogen Chemical Control of Fungi

Resistance issues with Fungicides

Pathogen Chemical Control of Bacteria

Antibiotics and Copper (Resistance issues)

Pathogen Chemical Control of Nematodes

Nematicides (no codumented field resistance)

Pathogen Chemical Control of Viruses

No direct chemical controls available