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Emergence of wheat blast in India and Bangladesh: an increasing risk for Europe?

Thierry M., Pordel A., Cros-Arteil S., Adreit H., Milazzo J., Kroj T., Morel J.B., Fournier E., Gladieux P., Loos R., Tharreau D.. 2018. Paris : EFSA, p. 5-6. International Conference on the Impact of Global Change on the Emergence of Plant Diseases and Pests in Europe, 2018-04-23/2018-04-24, Paris (France).

In Europe, wheat is the most widely planted food crop and the leading source of plant proteins in human food. In 2016, 62 M ha were planted and 250 M T were harvested in Europe (vs 220 M ha and 749 M T worldwide; source FAOSTAT). Wheat blast, caused by the fungus Magnaporthe oryzae, emerged and is a devastating disease of wheat in South America. It severely threatens wheat production in Brazil (30% yield loss in 2010) where the first outbreaks were reported 30 years ago (http://blog.cimmyt.org/?p=3707). In 2015, the disease emerged in Bangladesh (Islam et al. 2016) and spread the following year to India. Phylogenetic studies based on whole genome sequence clearly showed that this outbreak was due to an introduction from South America (Islam et al. 2016). The origin of wheat pathogenic strains in South America is debated but experimental (Farman et al. 2017) and phylogenetic studies (Gladieux et al. 2017) support a host jump from Lolium. This genus encompasses a cultivated grass (Lolium perenne) but also common weeds. We recently identified M. oryzae as the causal agent of epidemics on cultivated Lolium in France (unpublished data). Non-scientific reports suggest that it is also present in neighboring countries. The emergence of wheat blast in Europe would likely cause a large spread of the disease and major yield losses on this crop. There is an urgent need to 1) inform about the risk, 2) promote measures to prevent the introduction of the pathogen, 3) carry out research work to measure the risk (susceptibility of wheat varieties cultivated in Europe, presence of potential sources for host jump…), 4) develop surveillance methods and network, and 5) set up eradication plans to be used if the disease emerges.

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