Genetics against pests
Oxitec tested gene drive against caterpillars
Sergey Kolenov, N+1
The British company Oxitec has tested a gene drive technology to combat corn leaf scoops (Spodoptera frugiperda) — dangerous pests of agriculture. Experts have modified the males of these butterflies in such a way that their female offspring are not viable. It is assumed that this approach will significantly reduce the number of scoops. As reported by New Scientist, preliminary field tests of the technology in Brazil were successful. As expected at Oxitec, the modified males mated with wild females. However, the effectiveness of the technique has yet to be evaluated.
Pesticides and other poisons are commonly used to control agricultural pests, vectors of infectious diseases and invasive species. However, this approach is not ideal. Firstly, chemicals often cause serious damage to entire ecosystems. Secondly, the living organisms against which these compounds are directed eventually develop resistance to them — or learn to avoid them.
An alternative solution is the technology of gene drive, which allows you to fight a specific undesirable species without harming everyone else. Its essence is as follows. Specialists grow individuals of a certain species in the laboratory, in whose DNA a mutant gene is artificially introduced, and then release them into nature. Here they mate with wild relatives — but the offspring turns out to be unviable due to the mutation transmitted to it. If enough modified individuals are released, the number of the local population of the species can sharply decrease until extinction.
Most often, gene drive is proposed to be used to fight mosquitoes that spread a number of dangerous diseases. For example, the British company Oxitec has created genetically modified males of yellow-horned mosquitoes (Aedes aegypti). When they mate with wild females, they produce offspring unable to live to adulthood. Last year, the company began field testing of the technique in the Florida Keys, and this year plans to expand the scale of the experiment and release about two million modified mosquitoes in Tulare County, California.
Oxitec intends to use the gene drive against other dangerous insects as well. One of them is the corn leaf scooper (Spodoptera frugiperda), a moth whose caterpillars cause serious damage to corn and other agricultural crops. This species is native to North and South America, but over the past ten years it has colonized many countries in Africa, tropical Asia and Australia. As a result, the yields of some crops have almost halved here.
Oxitec employees have introduced a gene into the genome of male corn leaf scoops that makes their female descendants unviable. At the same time, male descendants survive and spread the deadly gene throughout the population. Experts hope that by releasing such males into nature, it will be possible to significantly reduce the number of scoops. They admit that after some time the deadly mutation will disappear from the gene pool, which will allow the number of butterflies to at least partially recover. However, if the releases are large-scale and regular, it is possible to completely destroy entire populations of pests.
The company has already conducted the first tests of the technique on cornfields in the Brazilian state of Sao Paulo. Experts were able to confirm that genetically modified males mate with wild females. In future experiments, Oxitec will evaluate how effectively this approach reduces the number of scoops. Meanwhile, Brazilian regulators have already approved the release of modified butterflies across the country.
Genetic modifications occur not only in biological laboratories, but also in the wild. For example, the caterpillars of the eastern meadow owls (Mythimna separata) borrowed from the viruses parasitizing them the genes of proteins that kill the larvae of the riders.
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