Researchers warn of a stem rust that could have returned to the largest wheat producing region in the world.

S. Tveden-Nyborg & M. Patpour/Aarhus University.

Last year in Sicily, wheat crops were affected by a new and unusually harmful fungal infection, say researchers. Its spores could infect the harvest this year in Europe, which is known as the largest wheat producing region in the world.

Chris Gilligan, an epidemiologist at the University of Cambridge, UK said: “We have to be careful of shouting wolf too loudly. But this could be the largest outbreak that we have had in Europe for many, many years.” He leads a team that has been modeling the possible spread of the spores of this dreaded fungus.

Researchers released alerts on the 2nd of February revealing the existence of TTTTF, a kind of stem rust that is known for the peculiar brownish stain that sets as it destroys the wheat stems and leaves. The researchers addressed the issue at the Global Rust Reference Centre (GRRC), which is a part of Aarhus University in Denmark, and the International Maize and Wheat Improvement Centre (CIMMYT), the headquarters of which are located at Texcoco in Mexico.

Thousands of hectares of crops were destroyed last year in Sicily. Researchers say that the disturbing part is that the GRRC tests suggest that the fungus can infect several laboratory grown kinds of wheat, including the hardy varieties that are usually highly resistant to disease. Study of whether commercial crops are as susceptible is now being conducted by the team.

Another concern is that the centers claim that two new strains of a different wheat disease called yellow rust has been observed in large areas for the first time, one in North Africa and Europe and the other one in Central Asia and East Africa. The possible effect of the yellow rust fungus is not clear, but the virus seems to be similar to pathogens that have previously caused such epidemics in Afghanistan and Europe.

In Rome, the Food and Agriculture Organization of the United Nations (FAO) has issued similar alerts on the 3rd of February about three diseases.

Increases in food prices, economic stability and inflation are possible consequences of the wheat damage in Europe says James Brown, a plant pathologist at the John Innes Centre in Norwich, UK.

However, researchers hope that information sent out to farmers before the European wheat crops grow this year will help them monitor fields and apply fungicides and halt the spread of the diseases. Plant breeders can also increase efforts to produce disease resistant varieties.

“Timely action is crucial,” says Fazil Dusunceli, a plant pathologist at the FAO.

The stem rust returns

In the middle of the twentieth century devastation caused by stem rust spurred efforts taken to breed wheat strains that could resist the fungi. Agronomist Norman Borlaug, led the research and gave us the famous Green Revolution in agriculture, thus increasing crop yields around the world.

However, in the late 1990s and 2000s, the stem rust returned with a variety called Ug99, that spread all over Africa and some parts of the Middle East. It caused international concern and harmed crops, more than 90% of wheat crops were susceptible to it, says Fazil Dusunceli. So far, however, it hasn’t hit large wheat-producing regions such as Europe, China and North America.

“It’s not a challenge plant breeders have faced for many years,” says Brown.

However, the outbreak seen in 2016 in Sicily suggests that the disease has now returned. The durum wheat which is hardy and used to make pasta, could be affected says Mogens Hovmøller, who leads the GRRC’s testing team. But, it is too early to say whether this new infection could be as devastating as Ug99.

Gilligan’s team at Cambridge University has prepared models based on weather and wind patterns together with the UK’s Met office in Exeter and CIMMYT that say that the stem rust spores released during the Sicilian outburst may have been deposited all over the Mediterranean region. However, that doesn’t mean the infection shall spread, the spores could have been destroyed during the winter, but it is worrying enough for researchers to raise an alarm.

Hovmøller says that the yellow rust strains are also a concern. For Europe, the most alarming one is provisionally named Pst (new) and was seen in Sicily, Italy, Morocco and northern Europe in 2016. The fungus is relevant to a virulent strain that North America in the 2000s, but it is not clear how aggressive it is.

Early-warning system

Every year in Europe, researchers usually find one or two wheat rust strains and these must be guarded against but may not necessarily be fatal. However, the region has experienced a great influx of wheat pathogens since 2010, says Hovmøller.

He speculates that this could be due to milder winters and warmer autumns attributable to climate change, along with newer farming practices such as sowing wheat earlier in the season.

It could also spread due to international travelers that could potentially carry spores on clothes.

Hovmøller along with others will ask the European Research Council for funds in the next few weeks to set up an early warning system. This will help the partners including scientists, breeders and agrochemical companies in Europe to share diagnostic facilities and information about potential outbreaks.

Dusunceli says that the network could have mitigated the Sicily outbreak, which in turn would mean that a fewer number of spores could spread to different parts of the continent. “I would not question the necessity for an early-warning system,” he says.