Regulatory Control and Genetic Manipulation of Crops/Pests

Regulatory Control

  • Regulatory Control: Involves enacting laws to prevent the movement of insect or pathogen-infected crops from one area to another.

  • Applied through quarantine, inspection of plants in fields or warehouses, and sometimes eradication of host plants.

  • Aims to prevent entry and establishment of foreign plant and animal pests and to eradicate or suppress pests in limited areas.

Plant Quarantine

  • Quarantine: From Latin quarantum, meaning 40.

    • Originally, 40 days of isolation for ships and people from countries with bubonic plague and cholera.

    • Now, it's a legal restriction on the movement of plants and planting materials between countries or regions within a country.

  • Aim: To prevent the introduction and spread of pests and diseases to areas where they do not exist.

Government Agency Role

  • Prevent further spread of injurious plant pests already in the country.

  • Regulate domestic movement of plants and related materials via various transport means.

  • Governed by existing domestic plant quarantine laws and regulations.

Responsibilities:

  1. Issuance of Phytosanitary certificates.

  2. Reporting pest occurrences, outbreaks, and spread.

  3. Inspecting consignments of plants and plant products.

  4. Surveillance and maintenance of pest-free areas.

  5. Conducting Pest Risk Analysis (PRA).

  6. Ensuring phytosanitary security of consignments after certification.

  7. Addressing other phytosanitary issues.

Implementation

  • The Philippine Plant Quarantine Service, enforced by the Bureau of Plant Industry-National Plant Quarantine Services Division.

  • Legal basis: Presidential Decree 1433, as amended (Plant Quarantine Law of 1978).

  • Regulatory arm of the Philippine Department of Agriculture.

  • Prevents entry and establishment of foreign pests into the country, as well as the spread of existing pests, according to international standards.

Actions Carried Out

  1. Enforcement of Plant Quarantine Rules and Regulations.

  2. Bilateral discussions/negotiations (Market Access).

  3. Conducting Plant Pest Risk Analysis (PRA).

  4. Laboratory Analysis.

  5. Commodity inspection and Treatment.

  6. Post-Entry Quarantine.

  7. Registration/Accreditation of Importers, Exporters, Farmers/Growers, Treatment Facilities, and Treatment Providers.

  8. Pest Survey.

  9. Establishment of Pest-Free Areas (PFA).

  10. Formulation of rules, guidelines, and orders.

Example of Quarantine Implementation

  • Department of Agriculture, Bureau of Plant Industry.

  • Pest Risk Analysis and Phytosanitary Requirements for the Importation of Fresh Strawberry Fruits from the Republic of Korea (example).

  • Pest Risk Analysis establishes the necessity for phytosanitary measures.

Cases of Pest Intrusion

  1. Golden cyst nematode: Spread from Long Island to multiple upstate countries.

  2. Mediterranean Fruit fly: Repeated introductions, but reportedly eradicated successfully.

  3. Citrus canker:

    • Introduced into Florida in 1910, eradicated after 21 years and 2.5 million.

    • New outbreaks occurred later in 1984, 1995, 1997, and 1998.

  • Quarantine provides time for alternative control measures.

Control of Pests and Diseases

Basic Principles:

  1. Exclusion: Prevents the introduction of a disease-causing agent (pathogen) into an area.

    • Interception: Detection of pests and pathogens in plants/parts en route to uninvaded areas.

      • Direct inspection: Examining planting materials (microscopic, serological detection).

      • Deferred inspection: Post-entry examination with random samples grown in a greenhouse for one year.

    • Rejection: Refusal to admit entry of imported material into an uninvaded area.

    • Elimination: Removal or incapacitation of the pathogen.

      • Sorting infected materials.

      • Disinfection (chemicals).

      • Disinfestation.

    • Prohibition: Complete prevention of entry of materials from countries where the disease is prevalent.

      • Quarantine personnel identify the country and host species.

  2. Eradication: Eliminates a pathogen after introduction and before establishment.

    • If total eradication isn't possible, reduce inoculum density.

    • Methods include:

      • Disinfection (systemic chemicals, hot water, dry heat, chemical treatment).

      • Roguing.

      • Crop rotation.

  3. Protection: Establishes a barrier between the pathogen and the host plant.

    • Assumes pathogens are present, and infection will occur without intervention.

    • Strategies: Chemical barriers (fungicides, insecticides), physical, spatial, or temporal barriers.

  4. Resistance: Selecting plants with the ability to remain healthy even if infected.

Legislation

  • Enacted laws to restrict movement of organisms with "Pest Potential".

  • Cost of exclusion is low compared to control costs after pest invasion.

Categories of Legislation

  1. Foreign Quarantine: Prevents the introduction of new pests from other countries.

    • Restricts or prohibits import of plant material (e.g., sugarcane sets from the Philippines, rubber seeds from America).

  2. Domestic Quarantine: Prevents the spread of dangerous pests within a country.

  3. Enforcement of Pest Control Measures: Requires cultivators to take control measures for established pests.

    • Examples: Cottony cushion scale, Coffee berry borer, Sugarcane top borer, Cattle fly.

  4. Quality Control: Prevents adulteration and misbranding of insecticides.

    • "Insecticide Act 1968" regulates import, manufacture, sale, transport, distribution, and use of insecticides.

  5. Regulation of Pest Control Personnel: Ensures safety for workers and the public; governed by the Insecticide Act 1968.

Restrictions on Import

  • Permission needed from the National Bureau of Plant Genetic Resources.

  • Import permits required.

  • Phytosanitary certificate from the country of origin needed.

  • Quarantine inspection at notified ports.

  • Fumigation of imported materials based on need.

Export Procedure

  • Exporter accreditation is necessary.

  • Bureau of Plant Industry-Quarantine Service develops protocols for acceptance of Philippine Exports.

  • Exportation involves sending goods from one country to another; must comply with import requirements.

Introduced Pests (Philippines)

  1. Coconut scale insect: Affected 1.2 million coconut trees in CALABARZON.

  2. Golden apple snail: Introduced from S. America; became a rice pest.

  3. Leafminer: Introduced with chrysanthemum importation; major pest of potato and ornamentals.

  4. Spiraling whitefly: Introduced with ornamental kalanchoe in the 1970s.

  5. Rice black bug: Problem in Mindanao and Leyte; introduced through vessels from Palawan and countries south of the Philippines.

  6. Potato cyst nematode: Introduced in potato planting materials; infesting farms in Benguet.

Integrated Pest Management (IPM)

  • Prevention is better than cure.

Genetic Manipulation of Crops

Historical famines

  • Bengal Famine: 1943; Estimated 1.5 to 4 million deaths due to starvation and disease.

  • Irish Famine (1845): Late blight of potato caused by Phytophthora infestans.

  • Bengal Famine: Bipolaris oryzae (1942), West Bengal, India.

  • Coffee rust: Hemileia vastatrix (1868), Sri Lanka.

  • Wheat rust: Puccinia graminis f.sp.tritici (1940), U.S.A.

  • Southern corn leaf blight: Helminthosporium maydis, U.S.A.

Insect Pest Control

  • A continuous process due to pest evolution.

  • 1938: Bacillus thuringiensis developed as a microbial insecticide.

  • 1940s: Synthetic pesticides became major control measure.

  • 1960s: Wide implementation of IPM approaches.

Genetic Manipulation

  • Methods for crop improvement:

    • Introducing variation.

    • Selecting useful variants.

    • Field-testing selected lines, hybrids.

    • New techniques to introduce variation: cell fusion, somaclonal variation, chemical or x-ray mutagenesis, and genetic manipulation.

Plant Breeding

  • Science of manipulating plant species for improved traits like disease resistance, pest resistance, salt/drought tolerance.

Genetic Manipulation Definition

  • Introducing a gene for a specific character into a cell's chromosome.

  • The result is a transgenic plant, exhibiting traits governed by the new gene.

Host Plant Resistance

  • Characters enabling a plant to avoid, tolerate, or recover from insect attacks.

  • Heritable characteristics influencing the degree of damage by insects.

  • The relative ability of a plant to overcome the effects of a pathogen. It ranges from a very low level to a very high level

  • Resistance inhibits insect population growth or helps recovery from injury.

Definition of Terms

  • Host plant: Plant species attacked by pests.

  • Immunity: Inability of an insect to attack a host plant.

  • Resistant: Host plants with lesser damage when attacked.

  • Susceptible: Host plant easily damaged by pests.

  • Horizontal resistance: Resistance to multiple races of a pathogen.

  • Vertical resistance: Resistance to specific races governed by a single or few dominant genes.

Importance of Host Plant Resistance

  • Develop techniques to screen for insect pest resistance under optimum infestation and environmental conditions.

  • Develop systems for insect rearing and refine screening techniques.

  • Establish long-term programs to screen and breed for resistance to multiple insect species.

  • Demand for cultivars with multiple resistance to insect pests and diseases for sustainable crop production.

Techniques

  • Techniques to screen for resistance to pests have been developed.

  • Resistant cultivars with desirable agronomic backgrounds have been developed.

Mechanisms of Host Plant Resistance

  1. Non-preference (Antixenosis): Insect response to unattractive host plant characteristics for feeding, oviposition, or shelter.

    • Involves the insect's behavior, not the host plant itself.

    • Host plants lack desirable characters like texture, hairiness, taste, flavor.

  2. Antibiosis: Adverse effect of the host plant on the insect due to toxic substances or lack of nutrients.

    • Plants with antibiosis have less damage.

    • Adverse effects: reduced fecundity, decreased size, longer life cycle, failure of pupation/emergence, increased mortality.

    • Indirect effect: increased exposure to natural enemies.

  3. Tolerance: Plants withstand insect damage by producing more tillers, roots, leaves, etc.

    • Tolerance results from: general vigor, regrowth of tissues, stem strength, additive branches, efficient utilization of non-vital plant parts, compensation by neighboring plants.

Bases of Resistance

Morphological Bases

  1. Trichomes: Hair-like outgrowths on the epidermis of leaves, shoots, and roots.

    • Impact depends on density, erectness, length, and shape.

    • Insects have difficulty feeding on plants with trichomes.

    • Trichomes release sticky substances that trap or inhibit movement.

  2. Surface Waxes: Protect plant surface against desiccation, insect feeding, and diseases.

    • Affect feeding behavior of insects (probing, phagostimulants, deterrents).

    • Waxes: Esters of long-chain fatty acids and aliphatic alcohol.

    • Sense organs on insect tarsi and mouthparts receive negative stimuli from the plant surface.

    • Affects the feeding behavior of insects acting as phagostimulants, or feeding deterrents.

Examples

  • Plutella xyllostella larvae showed non-preference for leaf wax characteristics in glossy-leaved resistant Brassica oleracea L.

  • Sorghum: Epicuticular wax from younger plants deterred Locusta migratoria migratoroides.

  • Wax bloom on crucifer leaves deters Diamondback moth (DBM) feeding.

  • Onion with glossy foliage provides more resistance to thrips.

  1. Color: Exists naturally in leaves, petals, fruits, stems.

    • Genetic manipulation of plant color influences physical processes.

    • Certain colors are less attractive to insects.

    • Whiteflies are less attracted to red foliaged Brassica species.

    • Cotton cultivars with red leaves are less attacked by boll weevils.

  2. Thickening of Cell Walls and Cuticle: Affects penetration and feeding by insects.

    • Chickpea resistant to bruchids is associated with seed coat toughness.

    • Sugarcane varieties with strong mid-ribs are resistant to sugarcane top borer.

    • Rice varieties with thicker hypodermal layers are resistant to stem borers.

  3. Shape and Size: Can bring behavioral changes in insects.

    • Thick roots of turnips have less damage from turnip maggots.

    • Onion leaves with narrow angles are more attractive to thrips.

    • Pod damage from Helicoverpa armigera is correlated with pod circumference, length, weight, and seed weight in chickpea.

Anatomical Adaptation

  • Variations in plant structures contribute to insect resistance.

    • Corn with tight husks is resistant to corn earworm.

    • Wheat with solid stems does not allow sawfly larvae to bore through stems.

    • Sugarcane with low stomata numbers is associated with resistance to Melanaspis glomerate (scale insect).

Biochemical Bases

  • Divided into behavioral and physiological responses.

    • Cucurbitins in cucurbits provide antixenotic resistance against Luperini beetles.

    • Gossypol (cotton plant pigment) confers antibiotic resistance to Helicoverpa zea and Helicoverpa virescens.

Host Plant Resistance to Diseases

  • Disease resistance: Reduction of pathogen growth.

  • Disease tolerance: Plants exhibit little damage despite pathogen levels.

  • Pathogenicity: Ability of a pathogen to attack a host (includes virulence and aggressiveness).

  • Virulence: Severity or harmfulness of diseases.

  • Aggressiveness: Degree of damage caused by the pathogen.

Examples of Disease Management via Resistant Varieties

  • Wheat – rust (Puccinia graminis)

  • Cotton – wilt (Verticillium and Fusarium)

  • Kila F1 – clubroot disease

  • Soybean – soybean crinkle; soybean mosaic virus

  • Cucumber – F1 Verde King – tolerant to cucumber mosaic virus

  • Carrot – Taraki- tolerant to blight

  • Chili – F1 Exotica 22 – resistant to virus disease, leaf spot diseases

Host-Pathogen Interactions

  1. No relationship: The plant does not react to the pathogen.

  2. Plant antagonistic to the pathogen: Host secretes inhibitory compounds.

  3. Pathogen antagonistic to the plant: Pathogen secretes substances that damage the plant.

  4. Mutual antagonism: Results in inhibition or death of both pathogen and host tissue.

Disease Resistance Bases

Morphological Bases

  1. Cuticle: Chemical barrier to penetration by most pathogens.

    • Young tissues are more susceptible due to thinner cuticle.

    • Wax layer offers resistance to penetration.

    • Wax induces water run-off, limiting infection droplets.

  2. Stomatal structure: Pathogens that penetrate through stomata are held back by closed or narrow stomata.

  3. Pre-formed substances: Present before infection.

    • Example: onion varieties with colored scales resistant to smudge due to catechol and protocatechuic acid.

Ecological Resistance (Pseudoresistance)

  • Relies more on environmental conditions than genetics.

Types

  1. Host evasion: Plant passes through susceptible stage quickly or when pests are fewer.

  2. Induced resistance: Increased resistance from changes in nutrients or water.

  3. Host escape: Lack of infestation due to transitory circumstances (incomplete infestation).

Transgenic Plant / Genetically Modified Crop

  • Plant with gene(s) artificially inserted, not acquired through pollination.

  • Transgenic plants produce continuous insecticidal proteins.

  • Bacillus thuringiensis (Bt) gene produces protein crystals toxic to Lepidopteran insects.

  • GM crops examples: canola, corn, cotton, potato, soybeans, tomato, alfalfa.

Transgenic technology

  • Traits:

    • Crop protection: resistance to pests, diseases, and herbicides

    • Abiotic stress: tolerance to drought, heat, cold or salinity

    • Quality traits: enhanced nutrition, shelf-life, or taste

Genetic Manipulation of Pests

Beginnings:

  • 1895: W.K. Rontgen - discovered X–rays

  • 1903: C. Bohn - reported effects of x-rays on insect reproduction.

  • 1916: G.A. Runner - found that low X-ray doses decreased reproduction in cigarette beetles; higher doses killed the insects.

  • 1926: H.J. Muller - X-ray radiation causes heritable changes in fruit flies.

  • 1937: E.F. Knipling - conceived insect control using chemical/physical sterilization.

Manipulation Aims

  • Reduce the fitness of the pest.

  • Decrease or eradicate the population.

Sterile Insect Technique (SIT) / Sterile Insect Release (SIR)

  • A form of genetic pest management tactic.

  • Uses sterilized insects by radiation or other means.

  • Pioneered by F. Knipling.

Chemosterilants

  • Chemicals affecting fertility; act in different ways.

  • Antimetabolites inhibit the utilization of essential metabolites

    • Greatest effect is on the female and usually results in infecundity

Advantages over irradiation sterilization:

  • Relatively cheap.

  • Do not require expensive apparatus to apply them

  • Can be applied orally, topically, by injection, by spraying, by dipping, by fumigation, or by exposure of the insect to a treated surface

Common SIR Procedure:

Steps

  1. Mass rearing of the target insect species (male)

  2. Sterilizing the insect with ionizing radiation or chemosterilan ts

  3. Releasing in large enough numbers to increase the probability of successful matings in the wild population

SIR Demonstrations

  • Use to eliminate the Mediterranean fruit fly invading California.

  • Use to contain the spread of pink bollworm infecting cotton.

  • Use to control coddling moth on apples and pears.

  • Use in Guimaras Province to control ango fruit fly.

Limitations of SIT

*Geography: Eradication zone must have natural barrier or defensible borders to prevent or reduce the immigration of the target pest from outside.
*Resistance: Native females may be able to recognize and refuse to mate with sterile males.Economics: Cost of rearing, sterilizing and releasing a large number of insects can be very high and need to be justified (EIL).

  • Desirability of sterile male: lab-reared and sterilized males must be equally or more competitive than native males in mating with native females

  • Knowledge about the pest reproductive behavior, population dynamics, dispersal and ecology of the insect.

  • Timing: Development of the lab-reared colony must be synchronous with that of the wild population.

Advantages of SIT

  • Creates inverse density-dependent feedback, making it more efficient as the wild population decreases

  • The only Pest Management tactic whose fundamental objective is to drive a wild population to extinctionSpecific

More Advantages of SIT

  • Environmentally friendly

    • Does not contaminate natural food chain

    • No threat to human health

  • Dominant Conditional Lethal Mutation

    • release of GM insect with dominant, conditional lethal trait

Advantages over irradiation sterilization

  1. Relatively cheap

  2. Do not require expensive apparatus for application

  3. Can be applied in different ways- orally, topically, by injection, spraying, dipping fumigation or exposure of insect to treated surface

Other Genetic Strategies

Inherited /Delayed Sterility

  • alternative genetic strategy to SIT

  • genetic alterations were induced by low dose radiation, reciprocal translocations, and genetic transformation with a conditional lethal trait

  • Conditional Lethal Mutation in this trait, strains of insect are produced that is detrimental to the species
    Conditional Lethal Mutation

  • inability to diapause (conditional lethal in an insect that has to go into diapause to survive a host-free period; in the laboratory no diapause is needed

  • Behavioral Changes advantageous to cause changes in the specific insect behavior

  • Hybrid Sterility could be raised in the laboratory and released into native populations

Behavioral Control

THREE PRINCIPAL ELEMENTS OF BEHAVIOURAL MANIPULATION METHOD Any behavior of any stage of the pest can be chosen provided that its manipulation protects the resource

Behavioral Control Definition

  • Dispense a large amount of sex pheromone within the crop in order to disturb the normal behavior of male insects so that they cannot find the female, hence interfering with mating

  • utilizes some chemicals to modify insect pest behavior and control pest without the use of toxins

Hormones are used to change the function and behavior of the animal

Semio-chemicals

  • Generic name for chemicals that act as STIMULUS and MEDIATE interactions among organisms

  • Chemicals that are active in very minute doses are utilized to modify the behavior of insects for the manipulation and regulation of their populations

  • AIM: to decrease population levels to improve disparity between general equilibrium and threshold

Classes of Semio-chemicals

Pheromones Intraspecific communicators

  • the behavior of the recipient this type of pheromone elicits a rapid response but is quickly degraded
    *Primer triggers a change of developmental eventsTerritorial pheromones mark the boundaries and territoryMark their trails to follow each othersex pheromones indicate the availability of the female for breeding or convey information about their

Function

The classification of pheromones based on function

  • Aggregation Pheromones use to gather members of the same species, in relatively big number

  • Alarm Pheromone Warn members of the same species about impending dangerIn Plant pheromones also exist certain plants emit pheromones when grazed

  • Territorial- pheromones mark the boundaries and identity of an organism’s territory

  • Trail Pheromoneused by ants to mark their trails to follow each other common in social insect

  • Sex Pheromoneinvolved in reproduction by attracting the opposite sex

  • Host marking pherommoneused by parasitoids to avoid ovipositing on host they or somebody else have oviposit alreadyhyper parasitoids may use these marking pheromones to find their hosts

Allelochemical

Chemicals that are significant to individuals of species different from the source speciesBest known microbial allelochemical is delta-endotoxin released by Bacillus thuringiensis

SYNOMONE

*Substance produced or acquired by an organism that evoks a reaction behaviorally

APNEUMONE

Substance emitted by a non-living material

ANTIMONE

Substance released by organism occasionally produces responses

APPLICATION OF SEMIOCHEMICALS IN IPM

  • Monitoring and AttractantUse of sex pheromones used to monitor insect pest incidence and abundancefood attractants for montitoring insect activity.

  • MASS TRAPPING Requires in large numbers.

  • MATING DISRUPTIONWhen the area is saturated with appropriate pheromone, causes confusion

  • Attractive lures and toxic lures secondary plant substances

Regulatory Control

Control where laws are enacted to prevent movement of insect or pathogen infected crops from one area to another.

Quarantine and inspection

Quarantine-
assurance that items for import are free of problem pests inspections from the exporting country or from the warehouses are done

Crop certification

Sellers of agri products submit to voluntary inspections or indexing of their crops in the field and in the storage by the state regulatory agency