From: wolda002@umn.edu
Date: Sat Mar 21 2009 - 19:50:24 EST
'Stem rust' fungus threatens global wheat harvest
New variety of an old crop disease called “stem rust” can infect crops
in just a few hours. Photograph: Steve Satushek/Getty images
The world's leading crop scientists issued a stark warning that a deadly
airborne fungus could devastate wheat harvests in poor countries and lead
to famines and civil unrest over significant regions of central Asia and
Africa.
Ug99 — so called because it was first seen in Uganda in 1999 — is a new
variety of an old crop disease called "stem rust", which has already spread
on the wind from Africa to Iran. It is particularly alarming because it can
infect crops in just a few hours and vast clouds of invisible spores can be
carried by the wind for hundreds of miles.
Scientists meeting in Mexico this week at a summit on Ug99 worry it will
continue travelling east and infect major wheat growing centres in
Pakistan, India and Bangladesh, which produce nearly 15% of the world's
wheat and feed more than a billion of the world's poorest people. Plant
breeders are now racing against time to develop new resistant wheat strains
and distribute the seeds around the world.
The fungus was thought to have largely disappeared since the 1960s when
original disease-resistant varieties were developed and planted. But Ug99
has evolved to take advantage of those varieties, and it is now believed
that 80-90% of all wheat varieties grown in developing countries are
susceptible to the new fungus.
The Nobel prize-winner Norman Borlaug, who is credited with helping India
and other countries avoid famines in the 1960s by developing high yielding
crop strains, said: "This thing has immense potential for social and human
destruction. It is capable of severely damaging virtually all of the
world's commercial bread wheat. It is a problem that goes far beyond wheat
production in developing countries. Sooner or later it will be found
throughout the world, including North America, Europe, Australia and South
America."
The new version of what scientists believe was one of the Biblical plagues
has spread from Uganda to Kenya, and then to Ethiopia and southern Sudan.
Where the spores attack, a wheat crop can be turned into a tangle of
blackened and broken stems in a few days. Up to 80% yield losses were
recently recorded in Kenya and Uganda, though fortunately neither of these
countries wholly depends on wheat as a staple crop .
But in 2007, it jumped the Red Sea, possibly as a result of Cyclone Gonu,
and is now widespread in Yemen and Iran. Wheat is a major crop in Iran, but
its progress has been slowed by a long-term drought that has inhibited its
growth.
"Kenya is having recurring epidemics, the situation is getting worse in
southern Sudan and it is now widespread in Ethiopia," said Rick Ward,
co-ordinator of the Durable Rust Resistance in Wheat project, based at
Cornell university. "The likelihood is that it has already spread beyond
Iran. We would be foolish to believe that other countries in central Asia,
such as Afghanistan and Pakistan, are not already at risk. Places like
Kazakhstan, Turkey, Ukraine are all susceptible."
Ward predicted that Ug99 would inevitably spread much further, potentially
into regions where wheat is a staple crop for hundreds of millions of
people. "It is a certainty that it will expand its area," he said. "It will
continue to move and wherever it is present and the crops are susceptible
it will potentially lead to a disaster of catastrophic proportions, which
will translate into widespread food insecurity and civil unrest." Global
wind models suggest the crop disease may next spread into Pakistan,
Afghanistan and India.
Large wheat farmers in developed countries can buy expensive fungicides,
which they must apply several times to protect their crops, but very few of
the small farmers in Asia can afford the chemicals.
However, scientists at the meeting reported rapid progress in developing
newly disease-resistant wheat varieties. According to plant geneticist Ravi
Singh, a project leader at the International Wheat and Maize Improvement
Centre in Mexico, 60 disease-resistant varieties have been developed via
conventional breeding, some of which are thought to be not only resistant
to Ug99, but higher-yielding than today's most popular varieties. Countries
such as Bangladesh and Pakistan are already being helped to multiply
resistant seeds for future harvests, he said.
But it usually takes at least five years to cross disease-resistant lines
with wheat varieties adapted to local conditions and then grow enough seed
to plant fields. "We are making rapid progress but it will take years to
distribute enough new varieties" said Ward.
Ug99 "stem-rust" fungus
• Ug99 is resistant to the three major anti-rust genes used to protect
nearly all the world's wheat.
• The fungus reproduces to release billions of identical spores, which
can blow hundreds of miles in the wind
• It attacks the above-ground part of plants and unlike other strains,
can cause 100% crop loss
• The US army produced wheat rust as part of its biological weapons
programme in the 1960s
* guardian.co.uk © Guardian News and Media Limited 2009