UK scientists, in collaboration with groups in Europe and the U.S., have discovered why the green peach aphid (Myzus persicae) is one of the most destructive pests to many of our most important crops.
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Their research will inform industry and research programmes to support pest control and aid global food security.
Unlike most plant-colonising insects, which have adapted to live on a small range of closely related plants, green peach aphids can colonise over four hundred plant species.
Developing resistance to over 70 different pesticides, coupled with the ever changing climate affecting crop losses in the EU and UK, the pest wreaks havoc on crop yields.
The green peach aphid transmits over a hundred different plant viruses and the notorious insect feeds on essential crops such as oilseed rape, sugar beet, tomato and potato, as well as wild plant species, which may serve as sources of the plant viruses.
One key example is Turnip Yellows Virus (TuYV), which if left uncontrolled can reduce yield of multiple crops, such as oilseed rape and sugar beet, by up to 30%, rendering some crops unprofitable in the UK.
The aphids spend winter living on host plants such as peach, apricot or plum, but in the summer months can colonise a huge range of vegetables – from potatoes to spinach, squash, parsley and parsnip.
Generally, insect parasites that live on a certain plant species are genetically adapted to one plant variety alone.
However international research led by the Earlham Institute (EI) and the John Innes Centre (JIC), has found that the green peach aphids can tune their gene activity ‘up’ or ‘down’ in response to different plant hosts and environments.
More intriguing about the insect's strategy is that aphids can reproduce clonally – i.e. they produce genetically identical lineages.
This allows biologists to compare individual aphids with the same genetic background and see precisely what genes are more active than others in aphids living on different plant species.
As part of their research, the team grew aphid clones on three different species of plant. This enabled them to find the specific genes that were involved in colonising each different host plant.
It appears that the genes responsible for helping aphids adjust to different plants are found in clusters within the genome and are rapidly increased or decreased in two days of transfer to a new host plant species.
The team found that rapid changes in gene expression were vital for the green peach aphid’s generalist lifestyle.
Interfering with the expression of one particular gene family, cathepsin B, reduced aphid offspring production, but only on the host plant where the expression of these genes is increased. ■