Transcript Genetic manipulation in PM

“GM” in “PM”
Genetic manipulation in pest management
(pest population control)
Genetic manipulation in agriculture
• GM on crops
• GM on pests
Sterile insect technique / release method (SIT) / (SIR)
1.
2.
3.
Mass rearing of the target insect species (males)
Sterilizing the insects with ionizing radiation or chemosterilants.
Releasing in large enough numbers to reduce the probability of
successful matings in the wild population.
Kniplings Model
• The SIT was first described by E. F. Knipling in 1955.
• http://instruct1.cit.cornell.edu/courses/ipm444/07Gen
ManPest/mp1.htm
Edward F. Knipling
"I wanted to contribute to
agriculture in ways other
than pulling a cotton sack
down the row."
Some success stories…
•
Screwworm fly (Cochliomyia hominivorax)- eradicated from the
United States (1950s-90s), Netherland (Curaçao, 1954) and Libya
(1990-92)
•
Mexican fruit fly (Anastrepha ludens) eradicated from most of
northern Mexico.
•
Tsetse fly eradicated from Zanzibar (1970–1990s).
•
Medfly (Ceratitis capitata)- eradicated from northern part of
Chile and southern part of Peru and southern part of Mexico
(1970s–80s)
•
Sweet potato weevil (Cylas formicarius) eradicated from Kume
Island, Okinawa, Japan (1994-99).
Etc.…
Yuval et al., 2010. ISME J
What are the advantages of SIT?
• Creates inverse density-dependent feedback, making it more
efficient as the wild population decreases.
• The only PM tactic whose fundamental objective is to drive a
wild population to extinction.
• Specific
• Environmentally-friendly
– Does not contaminate natural food chain
– No threat/harm to human health has so far been reported
What are the limitations of SIT?
• Geography. The eradication zone must have either natural barriers (e.g.,
oceans, deserts, mountains) or defensible borders to prevent or reduce
the immigration of the target pest from outside.
• Economics. Cost of rearing, sterilizing, and releasing a large numbers of
insects can be very high and needs to be justified (EIL).
• Desirability of sterile males. The lab-reared and sterilized males must be
equally or more competitive than the native males in mating with the
native females. They may become less desirable after many generations
and need renewal.
• Knowledge about the pest. reproductive behavior, population dynamics,
dispersal, and ecology of the insect.
• Accurate estimation of the native population density
• Timing. The development of the lab-reared colony must be synchronous
with that of the wild population.
• Resistance. Native females may be able to recognize and refuse to mate
with sterile males.
Inherited / delayed sterility
• An alternative genetic strategy to SIT:
– requires fewer insects
– requires lower doses of radiation
• Released insects are fertile but their progeny are sterile.
• Genetic alterations induced by low dose radiation
– Reciprocal translocations
– genetic transformation with a conditional lethal trait
http://instruct1.cit.cornell.edu/courses/ipm444/07GenManPest/mp4.htm
The concept of Population displacement
• What may be the issues of completely eliminating a pest
species from an ecosystem?
– upsets the balance at higher trophic levels, food webs
– secondary pest
• The idea of Population displacement is that we are not just
eliminating the native pest species (AA) but replace it with a
genetically translocated counterpart (TT), in which AA and TT
are both fertile
– Only the hybrid (AT) would be sterile
– Replacement occurs If TT >> AA in the wild
• TT strains would have more preferable traits
– E.g. less damaging to crop, more sensitive to insecticides,
environmental stress, "booby trap" chemicals.
Dominant Conditional Lethal Mutation
• Release of GM insects with dominant, conditional lethal trait
• Example: