Ground Cover Supplement : GC Supplement - Biosecurity
15 BIOSECURITY GROUND COVER DIAGNOSTICS & PRE-BREEDING SHOULD KARNAL BUNT become established in Australia, the economic cost due to reduced wheat quality and loss of markets is considered to be extreme: studies have estimated 18 and as high as 25 per cent of the value of Australian wheat production could be lost. The development, by the Cooperative Research Centre for National Plant Biosecurity, of a new molecular assay able to detect karnal bunt, even if only a single spore is present, provides another barrier to help prevent an incursion into Australia. The assay could also offer the opportunity for Australia to be able to certify export grain as free from karnal bunt. Karnal bunt in wheat is caused by the fungus Tilletia indica. Attacking the flowers, it results in partially blackened grains that crush relatively easily and produce a fishy smell. Each diseased grain contains millions of spores that will affect the integrity of the wheat supply chain from farm to markets. The new molecular probe is able to detect T. indica and other related grass bunts found in wheat grains. The ability to correctly detect the presence of the bunt from a single spore removes the need to germinate spores, reducing risk and the time required for a definitive identification. Previously, up to 50 spores were required for a statistically valid result. Being able to distinguish T. indica from other very closely related bunts suggests the test should not be compromised by the presence of other unrelated fungal spores, such as rusts. The molecular assay is an added enhancement to current methods of identification that require spores to be assessed under a microscope. When spores are identified by the molecular assay, confirmation would be made using conventional microscopy. This enhanced surveillance protocol has been found to be significantly more economic and sensitive in areas where the pathogen is not expected to be present. This makes it an extremely valuable screening tool to safeguard against an incursion. The molecular assay has undergone a national and international 'ring test' involving state laboratories as well as labs in the UK, Italy and China. Obtaining international acceptance of the test is an important step as more than 45 countries have import restrictions on wheat contaminated with karnal bunt. The test will initially be used to help enforce Australia's strict quarantine regulation to prevent the entry of karnal bunt. In future, there is the opportunity to use the test to develop an accreditation to certify wheat is free from karnal bunt at export. This area requires further investigation. THE TEST CAN CORRECTLY DETECT THE PRESENCE OF KARNAL BUNT FROM A SINGLE SPORE. ANOTHER HURDLE FOR KARNAL BUNT There is a new test for what is considered the most serious exotic pest threat to Australia's wheat industry By Mui-Keng Tan The development of the test marks an important step forward in maintaining Australia's karnal-bunt- free status. However, further research is required to understand and identify different isolates of the T. indica fungus that are found in different regions. □ GRDC Research Code NPB00002 More information: Dr Mui-Keng Tan, senior research scientist, I&I NSW, 02 4640 6445, firstname.lastname@example.org; www.grdc.com.au/NPB00002 Karnal bunt in wheat attacks the flowers, resulting in partially blackened, fishy smelling grains, making it unmarketable.
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