Genetic Control of Pests and Plants
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Genetic Control of Pests and Plants

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What is one of the main advantages of using host plant resistance to manage pests?

  • It often requires high costs to implement.
  • Resistance is specific to a particular pest. (correct)
  • It is hazardous to the environment.
  • It takes a short time to develop resistant varieties.

    • Which of the following is NOT a disadvantage of using host plant resistance?

  • There is a lack of resistance to some polyphagous insects.
  • Resistant varieties may be compatible with most other agronomic traits. (correct)
  • Insects can develop new strains that evade plant defenses.
  • It takes time and resources to develop a resistant variety.

    • Which component must engineers insert to ensure the expression of the inserted gene in genetically modified crops?

  • An enhancer sequence from bacteria.
  • A structural protein.
  • A silencer sequence from plants.
  • A promoter gene from a virus. (correct)

    • What is a common example of genetically modified crops that are resistant to specific pests?

    <p>Bt corn and Bt cotton.</p> Signup and view all the answers

    What is a potential issue that arises if resistant varieties of crops are widespread and insect densities are high?

    <p>Insects may develop new strains that are resistant to the plant's defenses.</p> Signup and view all the answers

    What is considered a false resistance in plants against insect pests?

    <p>Ecological resistance</p> Signup and view all the answers

    Which mechanism of genetic resistance reduces the likelihood of a pest feeding on a plant?

    <p>Non-preference</p> Signup and view all the answers

    Induced resistance in plants is primarily developed through which of the following?

    <p>Proper care and farm practices</p> Signup and view all the answers

    What is a characteristic of antibiosis as a mechanism of resistance?

    <p>It harms the pest's health when they feed on the resistant plant.</p> Signup and view all the answers

    In the context of ecological resistance, what does phenological asynchrony refer to?

    <p>Timing of crop growth stages to avoid peak pest populations</p> Signup and view all the answers

    Which of the following effects may result from ingesting toxic substances found in resistant plants?

    <p>Malformations in insect development</p> Signup and view all the answers

    What is the primary advantage of using resistant varieties in pest control?

    <p>Better crop yields and disease resistance.</p> Signup and view all the answers

    What best describes the type of resistance achieved through genetic factors in plants?

    <p>Genetic resistance</p> Signup and view all the answers

    Which term is used to describe a plant's ability to thrive despite pest attacks?

    <p>Tolerance</p> Signup and view all the answers

    Which of the following rice varieties is known to be resistant to major pests and diseases?

    <p>Rc 160</p> Signup and view all the answers

    What type of resistance is pre-formed resistance described as?

    <p>Innate or passive type of resistance.</p> Signup and view all the answers

    What is the primary function of the hypersensitive reaction (HR) in plants?

    <p>To localize and kill the invading pathogen.</p> Signup and view all the answers

    Which of the following statements accurately describes induced resistance?

    <p>It develops after pathogen infection.</p> Signup and view all the answers

    Which of the following is NOT included in the pre-formed resistance mechanisms?

    <p>Production of phytoalexins.</p> Signup and view all the answers

    Which of these varieties was bred by PhilRice scientists?

    <p>Rc 300 (Tubigan 24)</p> Signup and view all the answers

    Which mechanism aids in preventing pathogen invasion due to nutrient deficiencies?

    <p>Pre-existing compounds.</p> Signup and view all the answers

    What is the primary technique used in the sterile insect technique (SIT)?

    <p>Mass-rearing and sterilization of insects</p> Signup and view all the answers

    Which chemical is noted as a sterilant used in SIT?

    <p>Tris-(1-aziridinyl) phosphine oxide</p> Signup and view all the answers

    What is one of the main advantages of the sterile insect technique?

    <p>It is a highly environmentally friendly approach</p> Signup and view all the answers

    What is a potential drawback of using tris-(1-aziridinyl) phosphine oxide in SIT?

    <p>It is both mutagenic and carcinogenic</p> Signup and view all the answers

    Which pest was successfully eradicated using the sterile insect technique in North and Central America?

    <p>Screwworm</p> Signup and view all the answers

    What does host plant resistance enable a plant to do?

    <p>Inhibit pest population growth</p> Signup and view all the answers

    Which of the following methods is used in conjunction with SIT to suppress fruit fly populations?

    <p>Methyl eugenol as lure and malathion as poison</p> Signup and view all the answers

    What is a key feature of genes from wild relatives of crops in terms of pest resistance?

    <p>They allow plants to recover from damage</p> Signup and view all the answers

    What role does phytoalexin play in plants?

    <p>It inhibits the development of the pathogen.</p> Signup and view all the answers

    What is indicated by systemic acquired resistance (SAR) in plants?

    <p>Plants infected by one pathogen become resistant to others.</p> Signup and view all the answers

    Which of the following is an example of a resistance elicitor?

    <p>Chitosan.</p> Signup and view all the answers

    What effect does a mild strain of a virus have on a healthy plant in relation to cross-protection?

    <p>It can protect the plant from an aggressive strain of the same virus.</p> Signup and view all the answers

    What is a major challenge in the traditional breeding of pest-resistant crops?

    <p>It requires multiple selfings and backcrossing steps.</p> Signup and view all the answers

    How does genetic modification improve the pest resistance of crops?

    <p>By introducing specific DNA sequences encoding insecticidal proteins.</p> Signup and view all the answers

    What is required for transferring a dominant resistance gene through traditional breeding?

    <p>At least four backcrossing rounds within seven seasons.</p> Signup and view all the answers

    What occurs after the genetic insertion of a resistance gene into a plant?

    <p>Selection of the target gene's offspring follows.</p> Signup and view all the answers

    Study Notes

    Genetic Control: Mechanisms of Genetic Manipulation of Pests and Host Plants

    • Sterile Insect Technique (SIT): A widely used genetic control method for insects. Involves mass-rearing insects, sterilizing them (using irradiation or chemicals), and releasing large numbers of males to mate with wild females.
    • SIT is environmentally friendly.

    Example of Chemical Sterilant

    • Tris-(1-aziridinyl) phosphine oxide is a chemical sterilant used in the SIT.
    • Drawbacks: mutagenic and carcinogenic to humans and animals, posing environmental hazards. Use with caution.

    Examples of Effective SIT Programs

    • SIT programs eradicated screwworms in North and Central America.
    • SIT programs also suppressed Mediterranean fruit fly populations in Florida and other locations.
    • SIT and MAT (methyl eugenol as a lure, malathion as a poison) were used to suppress fruit fly populations in Guimaras, Iloilo (1996-1998).

    Mechanisms of Host Plant Resistance to Insect Pests

    • Host plant resistance: Involves the heritable property that enables plants to inhibit pest populations and recover from damage.
    • Deployment of genes from wild relatives and novel genes in crops creates resistant plants.
    • This is a weapon to minimize insect losses.

    Mechanisms of Resistance in Plants

    • Plant resistance to insects: Enables plants to avoid or suppress pest selection (inhibit oviposition and feeding). Reduces insect survival, development, and tolerates or recovers from significant damage.

    Two Ways Plants Become Resistant to Insect Pest Attacks

    • Ecological resistance: A false or pseudo resistance. The crop's environment plays the primary role.
    • Genetic resistance: True resistance governed by resistance genes in the plant's genetic makeup.

    Types of Ecological Resistance

    • Phenological asynchrony: The crop's susceptible stage does not coincide with the pest's peak population.
    • Induced resistance: Proper plant care, such as fertilization, makes the plant resistant to insect pests.

    Mechanisms of Genetic Resistance to Insect Pests

    • Genetic resistance: Under the primary influence of the plant's genetic factors and is true resistance.
    • Painter (1951) classification: Classified insect resistance into non-preference, antibiosis, and tolerance.
    • Antixenosis (non-preference): Pest is less likely to find or feed on a resistant plant.

    Antibiosis

    • Plant feeding harms the pest's health or fitness.
    • This often involves chemicals in plant tissues that either kill, slow development, or reduce the reproduction of the pest species.
    • Physiological effects of a plant's ingestion by an insect.

    Tolerance

    • The plant can continue to thrive despite pest attacks.

    Host Plant Resistance to Diseases

    • A host plant's ability to exclude or overcome a pathogen's effect.

    • Resistant varieties are the best pest and disease control method.

    • Plant varieties respond uniquely to specific pathogens.

    International and National Plant Breeding Institutions

    • Organizations develop resistant varieties (e.g., IRRI for rice, CIP for potatoes). Table details numerous institutions and crops.

    Rice Varieties with Pest Resistance

    • High-yielding rice varieties, such as NSIC Rc 216, Rc 160, Rc 300 (Tubigan).
    • Newer breeds like Rc 222 (Tubigan 18s) were developed
    • Rice Tungro disease resistant varieties (also known as "Matatag").

    Mechanisms of Host Plant Defense Against Plant Pathogens

    • Pre-formed Resistance: Passive defense mechanism.
    • Induced resistance: Active resistance mechanism.
    • Tolerance: Plant's ability to minimize the impact of a pathogen's infection on its health (despite infection).

    Preformed Resistance Mechanisms

    • Structural barriers: Thick cuticle, wax, partially closed stomates.
    • Compounds: Pre-existing compounds (e.g., catechol and protocatechuic acid).
    • Nutritional deficiencies: Lack of nutrients reduces pathogen growth.

    Induced Resistance Mechanisms

    • Pathogen-induced changes: Mechanical barriers, hypersensitive response (HR), phytoalexin production.
    • Pathogen toxicity reduction: Detrimental toxins neutralization

    Hypersensitive Reaction (HR)

    • Rapid localized death of host cells around the pathogen, confining its spread.
    • Lesions are small and localized.

    Systemic Acquired Resistance (SAR)

    • Initial pathogen infection can cause widespread resistance within a plant to other pathogens.
    • It builds upon a HR (hypersensitive reaction).

    Resistance Elicitors

    • Substances produced by pathogens or their parts that stimulate plant defenses.
    • These can induce plant resistance to other pathogens from the same or different class.

    Synthetic Compounds as Resistance Elicitors

    • Examples include: salicylic acid, aspirin, dichloroisonicotinic acid, chitosan.
    • These compounds activate defense responses.
    • Chitosan is effective against bacterial wilt in tomato, bacterial blight in rice, and bacterial heart rot in abaca.

    Genetic Modification of Crops for Pest Resistance

    • Time-consuming and resource-intensive process in plant breeding.
    • Backcrossing is needed. Dominant genes require fewer generations, recessive genes require more.

    Genetic Engineering of Crops

    • Short-cut to introduce pest-resistance genes.
    • Introduces specific DNA sequences (e.g., genes for insect resistance).
    • Transferred genes often encode proteins with insecticidal activity.

    Genetic Insertion Methods

    • Methods include: gene guns, bacterial vectors (Agrobacterium), chemicals, or electroporation.
    • A "promoter" gene from a virus is often included in genetic modifications to enable gene expression.

    Genetic Engineering Examples

    • Bt corn and cotton have genes from Bacillus thuringiensis for resistance to corn borers and cotton bollworms.
    • PRSV-resistant Hawaiian papaya is a result of adding ringspot virus coat protein genes.

    Advantages of Using Host Plant Resistance

    • Cost-effective
    • Specific to pests.
    • Compatible with other control methods
    • Long-lasting

    Disadvantages of Using Host Plant Resistance

    • Time consuming
    • Limited pest range
    • Potential for insect evolution
    • Compatibility issues

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    CPRT22 Module 5: Genetic Control PDF

    Description

    This quiz explores the mechanisms of genetic manipulation used in pest control and the measures for enhancing host plant resistance. Topics include the Sterile Insect Technique (SIT), its applications, and examples of its effectiveness. Additionally, it addresses the environmental impacts of chemical sterilants used in these methods.

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