Seeds of Destruction: Plagues

 Deuteronomy 28:59  Then the LORD will make thy plagues wonderful, and the plagues of thy seed, even great plagues, and of long continuance, and sore sicknesses, and of long continuance.

Thursday, April 19, 2007

A DNA-style hunt for the source of a wheat virus that attacked crops across the country led to an unexpected and disturbing culprit: Australia’s main wheat breeding seed quarantine station. By Cheryl Jones.

In 2003, news of an outbreak of the wheat streak mosaic virus in the CSIRO’s Canberra research facilities sent shockwaves through Australia’s agriculture sector, forcing scientists to destroy experimental crop plants and years of research.It was a scientific emergency that evolved into a mystery as the virus was detected in four states.

“If it’s endemic, it’s something that apparently … has not caused a lot of trouble in Australia,” Jim Peacock, then chief of CSIRO’s plant industry division and now chief scientist, told the ABC’s Science Show. The implication was that the trail had gone cold, so there was no point in tracking down the source.

One team of scientists disagreed.

The first breakthrough in solving the mystery of the invasion came in 2005, when a team of scientists led by Roger Jones, of the West Australian Department of Agriculture, demonstrated for the first time that the virus could be transmitted through wheat seed. They published their results in Plant Disease, journal of the respected American Phytopathological Society.

The scientists, using the same methods deployed to pinpoint HIV outbreaks, believe they have isolated the breach in the national shield: Australia’s main quarantine station for imported wheat breeding seed in Tamworth, NSW.

The virologists and geneticists believe the station may have unwittingly spread the wheat pathogen across the country, planting a biological timebomb set to go off as the drought breaks, seriously damaging our multi-billion-dollar wheat industry.

The research on the pathogen has implications for biosecurity and Australia’s lines of defence against the accidental or deliberate release of diseases that could cripple agriculture.

The virus, which has long depressed grain yields in America, Europe, Asia and North Africa, was first confirmed in Australia in early April 2003 when plants at two of CSIRO’s Canberra research facilities tested positive for it. Some plants had developed the classic symptoms - plant dwarfing, streaked or blotched leaves and shrivelled seeds.

The federal government and bureaucracy went into crisis mode. Scientists were consulted, committees convened and questions asked in parliament amid a rising media frenzy. The CSIRO destroyed experimental plants at its Black Mountain glasshouses and its field station at Ginninderra - needlessly, as it turned out - setting research back years. The government ordered a review of plant research biosecurity protocols, to be chaired by former CSIRO deputy chief executive John Radcliffe.

Meanwhile, the scientific method got blown up in the political minefield: claims were made in the media without the support of hypothesis testing and the rigorous process of peer review.

Soon after confirmation of the Canberra cases, the virus was detected in South Australia, Queensland, Victoria and NSW, and eradication was no longer considered an option. The CSIRO, which had been doing much of the running in the media, argued that the virus had been in Australia for a long time without doing much harm. The emergency seemed to have eased.

Before the team led by Jones showed that the virus could be transmitted through wheat seed, it was generally believed that the microscopic wheat leaf curl mite, which transmits the pathogen from infected to healthy plants, was the only way in which the virus spread.

Although the research team found that seed-borne infection rates were low, it argued that this mode of transmission could spread the virus rapidly across huge distances via international and national crop seed trade routes and breeding program distribution networks. The mite doesn’t usually travel far, but it can take over after the virus arrives in seed, spreading it from infected seedlings throughout a crop or region.

Some scientists had already suspected seed-borne transmission, known in related plant viruses, but most accepted the dominant paradigm.

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