New Phytol. http://doi.org/b8p5 (2017)

The wide adoption of transgenic cotton varieties expressing insecticidal proteins from Bacillus thuringiensis (Bt) has greatly reduced the use of broad-spectrum insecticides for this crop, but concerns over long-term off-target effects remain, and in any case not all insects are susceptible to Bt. Luo et al. demonstrate a subtler transgenic approach to control the sap-sucking plant bug Adelphocoris suturalis, using a DNA contraceptive rather than an insecticide.

Credit: JUPITERIMAGES/THINKSTOCK IMAGES/GETTY IMAGES

Several species of Adelphocoris have emerged as pests of cotton and other crops in China, America and India, not least because of their resistance to Bt. The researchers had previously identified a fatty acyl-CoA reductase (FAR), which they believed to be involved in pheromone production. However, reducing the expression of the AsFAR gene using RNA interference (RNAi) suppressed the development of ovaries in female A. suturalis and dramatically reduced their fertility. Luo et al. proceeded to create transgenic cotton plants, producing a 432-base-pair fragment of the AsFAR gene. When bugs fed on these plants, the double-stranded AsFAR fragment stimulated RNAi in the insect, suppressing expression of the AsFAR gene.

In field experiments conducted over two years, the transgenic cotton showed substantial resistance to A. suturalis infestation while having no detectable effect on other insect populations. Using targeted manipulation of an insect's reproduction could thus prove an effective and acceptable transgenic approach to limiting losses of crops to herbivory.