A blow-in from Australia causing significant problems for our eastern neighbour: wheat stripe rust in a disease nursery in New Zealand.
For many years, Australian and New Zealand scientists worked together closely to identify the cereal rust pathotypes (strains or races) that occurred in each country. However, this collaboration stopped in 2002 when permission to receive rust isolates from New Zealand was denied by Australian quarantine authorities.
Extensive historical data on cereal rust pathogen variability compiled prior to 2002 showed clearly that Australia and New Zealand form a single epidemiological unit as far as these pathogens are concerned. This finding was based on the occurrence of identical or very similar rust pathotypes in both countries.
Several examples showed that when a new pathotype appeared in Australia, it was then found in New Zealand one to two years later. Highlighting this pattern was the appearance of stripe rust in New Zealand in 1980, which followed its discovery in eastern Australia in 1979. Analyses indicated that the pathotype that appeared in New Zealand was the same as that found in Australia.
This and other cases have provided circumstantial but convincing evidence that aerial transport has carried rust spores on prevailing westerly winds more than 2000 kilometres across the Tasman Sea to New Zealand. In at least two cases, rust pathotypes have also spread from New Zealand to Australia; in these instances, the mode of transport is unknown.
Support from the GRDC, the Plant Biosecurity Cooperative Research Centre (PBCRC) and the Foundation for Arable Research (FAR) has enabled researchers at the Australian Cereal Rust Control Program (ACRCP), Plant & Food Research (PFR) and FAR to join forces in gaining understanding of the cereal rust pathotypes that now occur in New Zealand and how these relate to those in Australia. To overcome quarantine restrictions, ACRCP researchers have twice travelled to New Zealand to record results from greenhouse tests at PFR.
This New Zealand research involved preliminary screening of stripe rust in 2013 and a broader survey in 2014. Initial results confirmed that the Australian stripe rust pathotype 134 E16 A+ YrJ+ had crossed the Tasman to New Zealand. This pathotype is a mutant derived from the ‘WA pathotype’ and was detected in eastern Australia in 2007. Several other stripe rust pathotypes were also detected, most of which are thought to be related to the WA pathotype.
Seven wheat leaf rust pathotypes were identified from samples collected in 2014 in New Zealand. All were either the same or very similar to the leaf rust pathotypes occurring in Australia.
Findings from this preliminary research are consistent with earlier research showing strong evidence that cereal rust inoculum is regularly exchanged between the two countries, mostly from Australia to New Zealand on prevailing winds, but also, less frequently, by some unknown mechanism in the opposite direction. These study findings from 2013 and 2014 will be followed up in 2015-16.
This research has been further supported by the New Zealand Ministry of Business, Innovation and Employment.
Professor Robert Park,
02 9351 8806,
Dr William Cuddy,
02 9351 8871,
*Professor Robert Park (Plant Breeding Institute, University of Sydney), and from the PBCRC: Dr Soonie Chng (New Zealand Plant & Food Research) and Rachel Warre (NSW DPI), Dr Will Cuddy (NSW DPI).
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