Wheat blast is a relatively new disease of wheat caused by the fungus Magnaporthe oryzae Triticum pathotype (MoT). It was first reported in Brazil in 1985 and has become locally important in Brazil, Bolivia, and Paraguay since its emergence. In 2009, the dual wheat blast and Fusarium head scab epidemics in Brazil were estimated to have lowered the national wheat output by 30%. The South American (SA) strains of MoT are genetically diverse as evident in variable disease phenotypes on SA wheat genotypes. In 2012, wheat blast was reported on a single wheat plant in a research plot in Kentucky. Comparative genomic analysis of the Kentucky strain with an SA strain indicated that they emerged from different M. oryzae populations. The Kentucky strain most likely emerged in Kentucky from the gray leaf spot pathogen of annual ryegrass and was not introduced from SA. The SA strain appears to have emerged from wild grass populations of M. oryzae in SA.
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