Insects are easy to spot, fungus can appear quickly, but a virus – you can’t see a virus, especially in seeds or grains, when symptoms only develop in the plant.

A CRC for National Plant Biosecurity project is on target to change this situation, making diagnosis of plant and grain viruses faster and more accurate in quarantine through research involving the Grains Research and Development Corporation (GRDC) and the Victorian Department of
Primary Industries (DPI), supported by the Australian Quarantine and Inspection Service (AQIS).

Mid way through Phase II (2009–11) of the ‘Enhanced Diagnostic Platforms for Post Entry Quarantine and Market Access’ project, AQIS will soon have access to validated molecular diagnostic procedures using polymerase chain reaction (PCR) molecular testing to potentially detect one-third of all known grain viruses, including five of the 22 viruses listed under Australia’s Emergency Plant Pest Response Deed.

Phase I of the project concluded in 2008, producing reliable molecular diagnostic tests for the largest plant virus genus, a group of viruses known as the potyvirus genus. Additional tests have been designed for four virus genera important to the grains industry – furoviruses, hordeiviruses, tritimoviruses and rymoviruses. These tests are undergoing validation.

The AQIS senior manager southwest region, Mark Whattam, says AQIS facilitates the importation of more than
500 horticultural cultivars, 2,000 seed lines and 500 high-risk and 70,000 medium-risk ornamental plant lines/cultivars each year.

Globally, it is estimated more than 23 tonnes of wheat germplasm is shipped annually between breeders. Once wheat seed arrives in quarantine and after it is treated for insect risks and with hot water and fungicides, it is planted in post-entry quarantine areas and the resulting crops are assessed for virus symptoms.

CRC project leader Dr Brendan Rodoni, who is a senior plant virologist at the Victorian DPI Knoxfield Centre, says the development of the molecular tests provides AQIS with an accurate diagnosis rather than requiring staff to withhold a variety due to the suspicion of a virus.

“It will really make it easier for those poor pathologists working in the glasshouses trying to work out if or what virus is present,” he says. “We know there are some awful viruses in other parts of the world – like wheat spindle streak mosaic virus which enters the soil, acts like a nematode and is hard to kill – that we don’t want to let into
Australia.”

Although it will not necessarily speed up the quarantine process for winter cereals, Dr Rodoni says it will allow Australian agriculture and horticulture more security against viruses. It builds on gains already made in the horticulture quarantine processes, such as the reduction in approval time for new apple varieties from three years to 18 months.

He says it could also make a big difference by using DNA markers to analyse germplasm for the desirable agronomic traits plant breeders are seeking at the same time that molecular testing for viruses is undertaken.

This means some germplasm could be eliminated from the import process, saving a lot of time with further trials and testing.

Mr Whattam says AQIS is keen to provide feedback to the project in its endeavour to ensure relevant research results that can be used in its existing facilities.

“The CRC has access to a critical mass of specialist researchers and has invested significant resources in the development of new diagnostic techniques for use in the biosecurity continuum,” he says.

“AQIS is able to use the results of the research to better manage quarantine risks and support Australian exports. It is important to have the ability to test imported grain for viruses as it not only helps to protect Australian agriculture from exotic diseases, but also offers a rapid diagnostic test for Australian-grown grain, thereby protecting our valuable export markets.”

Last year the new testing protocols were tried on 450 cereal varieties from the Industry & Investment New South Wales collection housed at Tamworth. All proved free of these viruses and no false positives were detected. This year Dr Rodoni will travel to the United States, where he will meet with virologists from the US, Canada and New Zealand to ensure the same testing procedures are used with main germplasm trading partners.