Fungal disease endanger wheat production

Technical University of Munich (WeatherFarm) – Climate change has continued to pose a threat to yields and food security worldwide, with plant diseases as one of the main risks. A team of researchers led by Prof. Senthold Asseng from the Technical University of Munich has now shown that further spread of the fungal disease wheat blast could reduce global wheat production by 13 per cent until 2050.

With a global cultivation area of 222 million hectares and a harvest volume of 779 million tons, wheat is an essential food crop. Like all plant species, it is also struggling with diseases that are spreading more rapidly compared to a few years ago because of climate change.

One of these is wheat blast. In warm and humid regions, the fungus Magnaporthe oryzae has become a serious threat to wheat production since it was first observed in 1985. It initially spread from Brazil to neighbouring countries. The first cases outside of South America occurred in Bangladesh in 2016.

Researchers have modeled for the first time how wheat blast will spread in the future. South America, southern Africa and Asia will be the regions most affected by the future spread of the disease. Up to 75 per cent of the area under wheat cultivation in Africa and South America could be at risk in the future. Wheat blast will also continue to spread in countries that were previously only slightly impacted, including Argentina, Zambia and Bangladesh, according to researchers.

The fungus continued to invade countries that were previously untouched, including: Uruguay, Central America, the south-eastern United States, East Africa, India and eastern Australia. The risk is low in Europe and East Asia, with the exception of Italy, southern France, Spain and the warm and humid regions of south-east China.

Conversely, where climate change has led to drier conditions with more frequent periods of heat above 35 degrees Celsius, the risk of wheat blast may also decrease.

However, in these cases, heat stress decreases the yield potential. The affected regions are among the areas most severely impacted by the direct consequences of climate change.

Food insecurity is already a significant challenge and the demand for wheat continues to rise. In many regions farmers have to switched to more robust crops to avoid crop failures and financial losses. In the Midwest of Brazil, for example, wheat has been increasingly being replaced by maize.

Another important strategy against future yield losses is breeding resistant wheat varieties. The International Maize and Wheat Improvement Centre along with National Agricultural Research Systems released several wheat blast-resistant varieties which have been helpful in mitigating the effect of wheat blast. With the right sowing date, wheat blast-promoting conditions can be avoided during the ear emergence phase. Combined with other measures, this has proven to be successful.

Previous studies on yield changes due to climate change mainly considered the direct effects of climate change such as rising temperatures, changing precipitation patterns and increased carbon dioxide emissions in the atmosphere. Studies on fungal diseases have so far ignored wheat blast. For their study, the researchers focused on the influence of wheat blast on production by combining a simulation model for wheat growth and yield with a newly developed wheat blast model. Environmental conditions such as the weather are included in the calculations, as is data on plant growth. In this way, the scientists are modeling the disease pressure in the particularly sensitive phase when the ear matures.