Russian wheat aphid colony feeding on wheat.

Preparing Australia for a Russian wheat aphid invasion

CSIRO scientists are studying how Russian wheat aphid successfully overcomes resistance in wheat in order to protect Australian farmers from this devastating invasive pest.

• 2 November 2007 | Updated 14 October 2011

• Background
• Project aims
• Virulent RWA biotypes
• Molecular basis of RWA virulence

Background

Some overseas pest insects pose such a threat to Australian agriculture that it is necessary to have a preparedness strategy in place in case they get into Australia.

The Russian wheat aphid (RWA), Diuraphis noxia, is an example of such a devastating pest.

In the first seven years after its introduction into the United States of America (USA), the Russian wheat aphid caused American farmers over US$800 million.

Unlike most aphid species, just a few RWA can cause extensive damage to a wheat or barley plant by injecting toxins into the plant in their saliva.

Over the past 30 years, this insect has spread through all the major cereal-growing regions of the world except Australia.

One of the problems with controlling this pest is that it has demonstrated the ability to adapt to and overcome all the resistant wheat varieties that breeders have developed in the past.

Project aims

The aims of this research are:

• to understand how RWA is able to overcome resistance
• to identify resistance that RWA cannot overcome
• to work with breeders to develop Australian wheat and barley lines with durable RWA resistance so that our farmers will be protected from a future invasion of this pest.

Virulent RWA biotypes

Aphid strains, or biotypes, are called virulent when they can successfully feed on resistant plants.

Virulent RWA have been identified in a number of countries around the world, including:

• Mexico
• Syria
• Russia
• Hungary
• Chile
• Argentina
• the Czech Republic
• Ethiopia
• the United States of America
• South Africa.

CSIRO maintains a ‘living library’ of virulent RWA biotypes at its European laboratory in Montpellier, France.

With the help of collaborators in the USA (Dr Scott Haley, Colorado State University) and in Australia (Dr Mehmet Cakir, Murdoch University), we are testing new resistant lines of wheat against this biotype library to identify any resistance that is effective against all the virulent biotypes.

Molecular basis of RWA virulence

In collaboration with Dr Jerry Reeck at Kansas State University, as part of a Grains Research & Development Corporation (GRDC) funded project in the Cooperative Research Centre (CRC) for National Plant Biosecurity, we are comparing salivary gland genes between virulent and avirulent RWA biotypes. 

We need to know about the mechanisms of virulence to develop strategies to identify and manage RWA if it does enter Australia.

The mechanism controlling virulence in RWA must be in its saliva because this is the only part of the aphid that comes into contact with the plant.

This project is only possible because of emerging genomics resources in a model aphid species, the pea aphid, including a full genome sequence to be completed in 2008.

As little is known about the composition of aphid saliva, this project is producing a world-first molecular characterisation of aphid saliva.

We have already identified several genes which differ significantly between RWA biotypes, which in the short term provides us with a molecular diagnostic tool to identify the various biotypes.

In the long term, we hope that our understanding of the molecular basis of RWA virulence will help us to develop novel resistance mechanisms that this pest cannot overcome.

Read more about Biosecurity in CSIRO Entomology.