The re-emergence of a destructive cereal disease poses a threat to UK wheat production
14 July 2010
BBSRC scientists are advising farmers to change their fungicide regime to help prevent loses to a destructive cereal disease. Fusarium Ear Blight (FEB) is a destructive fungal disease of cereals including wheat and has the potential to devastate a farmer's crop just weeks before harvest. Over the last 10 years, on average, 38% of wheat crops in the UK had the disease. Scientists at Rothamsted Research, an institute of the BBSRC, have discovered substantial symptomless infection in wheat ears, which means that although the plant appears healthy the fungal infection could already be beyond the control of the farmer. Hence, our scientists are advising farmers to use fungicides as a preventative measure rather than a curative approach.
It is believed that the re-emergence of FEB is driven by changes to our climate and agronomic practices. For example, a greater likelihood of thunderstorms during crop flowering increases the level of infection, using reduced or minimal tillage leads to infected crop residues remaining on the soil surface and causes greater spore production, whilst growing maize, another susceptible cereal species, in the wheat rotation can increase disease levels. Besides dramatically reducing a farmer's yield, the harvested grains are also contaminated with a fungal toxin (mycotoxin) making them unsuitable and unsafe for human consumption, animal feed or malting purposes. Farmers in the UK pay the mill, where their grain is processed, to test for the presence of the mycotoxin and under EU safety guidelines approximately one infected ear per square metre would be sufficient for their harvest to be rejected. In 2008, 11.5 % of the wheat crop was found to be over the EU legal limit of contamination by the fusarium mycotoxin called deoxynivalenol (DON) and was rejected from use in the food chain and was downgraded for use as an animal feed or for various industrial purposes.
Attempts made to control the disease by traditional methods such as plant breeding and fungicide treatments have not been fully effective and may be costly. A definitive infection model of how the fungal pathogen spreads throughout the wheat ear, recently published in Fungal Biology, has been developed at Rothamsted Research, revealing why these control strategies have proven unsuccessful so far. Neil Brown, who did this research as part of his BBSRC-Syngenta-funded PhD said "when symptoms are showing on a couple of spikelets, up to one third of the ear is already fully infected."
Assessing the amount of infection in the harvest prior to sending grain to the mill could save the farmer time and money. At present assessments are done by scoring visible disease symptoms. The infection model from Rothamsted demonstrates that the amount of visible symptoms represent only a small proportion of the total infected area in each ear. Consequently, this approach could drastically underestimate disease levels and possibly mycotoxin contamination.
"By the time you spray when you see symptoms it is too late," Prof Hammond-Kosack said. "It needs to be a preventative spray as the ear is emerging out of the flag leaf - maybe a week to 10 days earlier than most growers spray."
This research also has implications for commercial wheat breeding programmes, which currently rely on scoring visible disease symptoms and determination of the mycotoxin levels in the final grain. Prof Hammond-Kosack said. 'The scoring of visible symptoms on ears should probably be phased out and efforts re-focused on accurately determining the levels of mycotoxin contamination in whole ears and the harvested grain. This would ensure that germplasm is identified which consistently lowers fusarium infections and results in low mycotoxin levels'.
Future research will investigate the possibility for the delivery of plant derived antifungal compounds designed to constrain the spread of infection or to inhibit the production of the fungal toxin. Research into how this pathogen causes disease, the identification of fungicide targets and novel control strategies are ongoing at Rothamsted.
Notes to editors
This study is published in the current issue of Fungal Biology as "The infection biology of Fusarium graminearum: Defining the pathways of spikelet to spikelet colonization in wheat ears" by Neil A. Brown, Martin Urban, Allison M.L. van de Meene and Kim E. Hammond-Kosack. The study was supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC). Neil A. Brown was supported by a BBSRC studentship with Syngenta as the CASE partner.
All the investigators are based within the Department of Plant Pathology and Microbiology at Rothamsted Research.
The research was done in conjunction with staff in Bioimaging at Rothamsted, a BBSRC-sponsored facility in partnership with Jeol and Gatan. Allison van de Meene is head of the Bioimaging group.
About Rothamsted Research
Rothamsted Research is based in Hertfordshire and is one of the largest agricultural research institutes in the country. The mission of Rothamsted Research is to be recognised internationally as a primary source of first-class scientific research and new knowledge that addresses stakeholder requirements for innovative policies, products and practices to enhance the economic, environmental and societal value of agricultural land. The Applied Crop Science department is based at Broom's Barn, Higham, Bury St. Edmunds. North Wyke Research is located near Okehampton in Devon. Rothamsted Research is an institute of the Biotechnology and Biological Sciences Research Council. www.rothamsted.ac.uk
BBSRC is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £470M in a wide range of research that makes a significant contribution to the quality of life in the UK and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.
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