http://www.independent.co.uk/news/uk/home-news/wheat-rust-the-fungal-disease-that-threatens-to-destroy-the-world-crop-9271485.html
Wheat rust: The fungal disease that threatens to destroy the world crop
Experts in Europe and Africa are racing to develop resistant grain
varieties as university researchers predict the likely spread across
continents of the air-borne spores of the fungus
Scientists are warning that wheat is facing a serious threat from a fungal
disease that could wipe out the world's crop if not quickly contained.
Wheat rust, a devastating disease known as the "polio of agriculture", has
spread from Africa to South and Central Asia, the Middle East and Europe,
with calamitous losses for the world's second most important grain crop,
after rice. There is mounting concern at the dangers posed to global food
security.
Experts have been aware of the threat since a major epidemic swept across
North America's wheat belt in the 1950s, destroying up to 40 per cent of
the crop. Since then, tens of millions of pounds have been invested in
developing rust-resistant varieties of the grain. However, an outbreak in
Uganda in 1999 was discovered to have been caused by a virulent mutation of
the fungus. There has been alarm at the speed at which further mutations
have subsequently developed and spread across continents.
Plant scientists in Britain estimate the latest developments mean that 90
per cent of all current African wheat varieties are now vulnerable to the
disease.
Last year, Germany witnessed its first outbreak of stem rust in more than
50 years. The outbreak was spurred by "a period of unusually high
temperatures and an unusually late development of the wheat crop due to
cold spring and early summer temperatures", explained Kerstin Flath, of
Germany's Federal Research Centre for Cultivated Plants.
A further outbreak occurred in Ethiopia last November, with farmers losing
on average 50 per cent of their wheat crop; the worst affected lost up to
70 per cent. Experts met in Mexico last month to discuss the threat. Work
is under way to examine the different strains, to identify similarities.
According to Dr David Hodson, of the International Maize and Wheat
Improvement Center in Addis Ababa, the disease's threat lies in its ability
to cause "large- scale destruction in a very short period of time over very
large cultivated areas". Rust epidemics could be compared to a forest fire,
Dr Hodson said. Once it manages to gain ground it can very quickly spread
out of control. The fungus reproduces millions of wind-borne spores, each
of which is capable of starting a new infection.
Fazil Dusunceli, of the UN's Food and Agriculture Organisation, said that
the fungal disease, along with drought, are major challenges to wheat
production globally.
He warned that countries need to react quickly to counter the new fungal
varieties: "Production of new seed varieties is critical." He said the UN
was looking to countries such as the US, Britain and other European nations
to lead the fight. "Developed countries have well-established institutions,
programmes and capacities that developing countries lack. The developing
countries are not sufficiently prepared to fight against these diseases and
so when epidemics occur they encounter significant losses," he said.
British scientists from the Sainsbury Laboratory, together with those from
the world-renowned John Innes centre, both in Norwich are in the vanguard
of efforts to combat the outbreaks. The UK teams are trying to control the
disease with genetics rather than develop more powerful chemical
fungicides. The work currently includes cloning new sources of resistance
from wild grasses and from barley, which they think is essentially
completely resistant to wheat rust.
Academics at Cambridge University, led by Professor Christopher Gilligan,
are using sophisticated mathematical models to help predict the likely
spread from outbreaks. "The project is designed to develop and test
mathematical models that can be used to improve understanding of when,
where and how disease spreads, which regions are most at risk and how to
control epidemics," Professor Gilligan said.
Using models from the UK Meterological Office, the Cambridge team were able
to predict the likely spread of the Ethiopian outbreak. "The results helped
to direct sampling teams to find further outbreaks, from which it became
apparent the epidemic was more severe and widespread than had been
previously reported." Further work by the modellers has identified which of
the countries surrounding Ethiopia in Africa, and the Middle East, are most
at risk. "The current evidence suggests that the risk of direct spread to
the Indian subcontinent is small during the winter months," Professor
Gilligan said.
"The models show, however, that the fungus could spread in stages, by first
infecting wheat crops in the Middle East and then spreading to other major
wheat-growing areas."
According to scientists, climate change is in part behind the threat. The
aggressive spread of two forms of the fungus is widely believed to be
linked to its rapid adaptation to warmer conditions. Dr Hodson said this is
resulting in outbreaks in countries not previously affected, with epidemics
in several countries from North Africa to South Asia.
"The result has been large-scale epidemics in many parts of the world and
stripe rust appearing in areas that were not considered favourable
environments for the disease. Conditions this year were extremely
favourable for rust development. In Ethiopia more than 600,000 hectares of
wheat were affected - about one-third of the total area under wheat
cultivation. Farmers suffered considerable production losses.
"Precise effects are difficult to ascertain. Certainly climate change is
having an influence, and will have an influence on pests and diseases in
terms of shifts in distribution patterns and shifts in the timing of their
appearance."
Pests and diseases are a major threat to agriculture around the world,
producing blights that cost farmers millions in lost production.
*Signs of blight*
Wheat rusts (yellow, leaf and stem rust) are fungal diseases that affect
wheat in almost every country in which it grows, as infectious spores are
transmitted by wind and through soil. Seven to 15 days after infection,
small red dots called uredinia begin to form on the leaf or stem surface.
The stem rust fungus, Puccinia graminis, attaches to another organism to
survive, killing the host in the process.
*Kill list*
*Pests and diseases are a major threat to agriculture around the world,
producing blights that cost farmers millions in lost production.*
*Asian soybean rust* affects the soya crop in Brazil - the world's biggest
producer. There are more than 244 confirmed cases this year. Industry
spending on insecticides and fungicides is expected to reach $11bn (£6.6bn).
*Cocoa pod borer disease* Cocoa bean production in Indonesia, the world's
third-largest producer, is likely to dip 2 per cent to 410,000 tonnes for
2013-2014, according to the International Cocoa Organisation. The fall is
in part due to a tiny, mosquito-sized moth which attacks the plant.
*Potato blight* is a fungus-like organism (above) that thrives in damp,
humid conditions. The speed with which blight infection occurs and the
devastating impact on the crop make it the biggest threat to the six
million tonnes of potatoes produced in the UK each year.
*Coffee leaf rust *is an orange-coloured fungus that has swept through
coffee fields from Mexico to Panama. The epidemic is affecting the
livelihoods of more than two million people and causing the loss of 500,000
jobs.
*Banana fungus (TR4)* This soil-borne disease is threatening banana crops
in North America, Europe, South-east Asia, the Middle East and Africa; the
value of traded bananas worldwide totals $8.9bn.
*Rozina Sabur*
Received on Sat Apr 19 2014 - 20:13:02 EDT