The US government has patented varieties of yeast and bacteria found naturally on wheat heads, as a way to control a costly disease of cereal crops worldwide.
Fusarium head blight (FHB), which is caused by the fungus Fusarium graminearum, is among the most costly diseases of cereal crops worldwide, including wheat, barley and oats.
At least 16 species of Fusarium can cause head blight, a disease that can reduce yields and contaminate cereals with toxins that can make grain unsafe for food or feed.
FHB became a serious problem in the US in 1993, when over 156 million bushels of wheat and 69 million bushels of barley were lost to FHB in the upper Midwest region alone. Since that time, although annual yield losses to FHB have declined somewhat from the record year of 1993, they have nevertheless remained high and currently stand at approximately 8 per cent of the crop.
From 1998 to 2000, these pathogens accounted for $2.7 billion in losses to US agriculture.
But the US Department of Agriculture (USDA) has now identified four yeasts and three bacteria that live on flowering wheat heads without causing any harm there as a potential means to keep the fungus at bay- some through the secretion of antibiotics.
The fungus infects wheat through its flower tissues, including anthers. But competition for space and nutrients there is fierce, according to studies by scientists at the USDA's Agricultural Research Service (ARS) National Center for Agricultural Utilization Research in Peoria, Illinois.
Plant pathologist David Schisler and colleagues at the ARS and at Ohio State University (OSU) in Columbus devised fermentation procedures to culture quantities of the beneficial microbes for application to flowering wheat heads, as a means to exploit this 'natural antagonism'.
The yeasts and bacteria that have been patented were the "top picks" from about 700 microbial specimens the scientists evaluated for their fungus-fighting prowess. Of these seven, yeast strain OH 182.9 performed the best in field trials, reducing FHB's severity in spring, winter and durum wheats by 20 to 60 percent.
"USDA's patenting of this approach to controlling FHB is a critical first step towards garnering the commercial interest necessary to develop the microbes as registered biological control products that can be used separately or in specific combinations on wheat or other cereal crops," said the ARS.
"Their development, along with more FHB-resistant wheat varieties, is especially appealing because the use of foliar fungicides is complicated by timing and availability by state," it added.
Last year, ARS scientists at Peoria developed a new DNA-based test to make the identification of fungi that cause FHB cereal disease easier to detect, by simultaneously identifying all of the major head blight pathogens and predict their toxin profiles.
At the time, the scientists had said that the test could be used to understand the distribution of these pathogens worldwide, as well as to determine if individual pathogen species prefer certain crops or environments.
This information is critical to the development of effective disease control strategies, including the production of cereal cultivars with broad resistance to Fusarium head blight pathogens.
Visual inspection is now used to spot these pathogens, but it cannot be used to identify which of the species is present in a field. To improve detection and epidemiology, the Peoria scientists devised a test that pinpoints nucleotide variations that genetically distinguish one head blight species from another.
The test relies on DNA 'probes'. When a probe matches the DNA in a head blight sample, the DNA is fluorescently labeled and detected using a special camera and a high-power laser, providing unambiguous identification of the head blight pathogen and its toxin potential. In addition, the test was designed to identify new head blight species.