Introducing genes for herbicide resistance into a crop permits it to be sprayed with weedkiller that really does then kill nothing but weeds. But that works only until the weeds themselves develop resistance to the poison. One way this can happen is through crossbreeding with the crop originally protected—a risk if weed and crop are closely related.
That is the case for rice, where weedy, natural varieties are a perennial problem because of the competition they bring to the cultivars farmers actually want to raise. But, as he describes in Transgenic Research, Lu Baorong, an ecologist at Fudan University in Shanghai, thinks he has found a solution. By adding a second transgene to the crop, he can sabotage any weed that crossbreeds with it. Dr Lu’s transgene encodes a genetic “silencer” that shuts down the expression of a natural gene called SH4. In wild grasses SH4 promotes a phenomenon called “seed shattering” that releases seeds from the stalk when they are ripe.
Dr Lu hopes to make [herbicides] more effective, by creating a cultivar in which silencers of SH4 and, perhaps, other seed-shattering genes are in close chromosomal proximity to the herbicide-resistance gene. That will mean any transfer of herbicide resistance automatically brings seed-shattering problems with it, stopping the spread of herbicide resistance within the weedy population.
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