Investment in aphid research

Less than a year since the detection of Russian wheat aphid in Australian cereal crops, new knowledge is emerging from Grains Research and Development Corporation research.

Now present in parts of Victoria, including the Wimmera, South Australia, Tasmania and southern New South Wales, the aphid, RWA, is the focus of an unprecedented level of Grdc-supported research aimed at helping the grains industry combat the pest.

The GRDC has been investing in research to confirm susceptibility of commercial wheat and barley cultivars to RWA; assessing potential sources of plant resistance; determining aphid biotype; RWA biology, ecology and economic thresholds under Australian conditions; an investigation into alternate hosts for RWA; trials looking at insecticide efficacy; and development of practical resources for growers and advisers.

GRDC disease traits manager Lauren Du Fall is overseeing key host resistance-related experiments – the first of their kind in Australia – being carried out by the South Australian Research and Development Institute and led by entomologists Greg Baker and Maarten van Helden.

One of those projects has involved assessing RWA susceptibility of current commercial varieties.

“A total of 85 Australian commercial lines have been screened for RWA susceptibility at the seedling to tillering stage,” Dr Du Fall said.

“A range of symptom expression was observed in a preliminary screen of a selection of current commercial bread wheat, barley and durum wheat varieties, indicating there might be a level of tolerance or resistance present in current commercial cultivars that could be further developed.

“However, susceptibility to RWA is a complex assessment and further data will be required to confirm these results, assess the impact on yield and determine whether it will be valuable to provide resistance ratings of varieties.”

Further data

Other work has focused on assessing sources of RWA plant resistance.

A glasshouse experiment involving diverse germplasm from around the world was screened with RWA to determine potential sources of resistance that might be used in breeding new varieties.

“Through assessing sources of resistance and the biotyping work, it appears we have access to germplasm with potential genetic resistance that could be developed through breeding to deliver Australian grain growers new resistant varieties, if that is considered to be an economically viable and sustainable approach to controlling RWA by commercial breeding companies,” Dr Du Fall said.

“We are really getting on the front foot here to provide breeders and industry with all of the information necessary to make informed decisions on the most appropriate strategy to manage RWA as an endemic pest to south-eastern Australia.”

Some of the germplasm screened exhibited higher levels of resistance than those of current commercial cultivars.

Although the plant resistance research is generating encouraging insights, Dr Du Fall said it must be remembered while plant resistance had been deployed as a management strategy in areas of the world where RWA was a serious risk, the aphid had responded through the evolution of new biotypes attacking these resistant plants.

While the introduction of RWA presents yet another pest for growers to control, experts supported by the GRDC believe it should be a manageable pest.

More information on management of RWA and links to relevant resources are available on GRDC’S website at www. grdc.com.au.