Wheat blast disease: danger on the move

Wheat blast is caused by the fungus Magnaporthe oryzae Triticum pathotype (MoT). The potential for wheat blast to cause widespread losses demands immediate action to understand and manage this explosive disease. The recent appearance of wheat blast in Bangladesh demonstrates the threat of global spread, which could occur via the movement of infected seed or grain. MoT mainly infects wheat heads, with symptoms closely resembling Fusarium head blight. To date, wheat blast is considered an intractable and dangerous disease and fungicides have shown limited efficacy. Disease management requires identification of new resistance sources and a complete understanding of MoT ecology and wheat blast epidemiology. Understanding the full potential for pathogen variability, including any role for sexual reproduction in the field, is critical. A small number of pathogen avirulence (AVR) genes block other host-adapted M. oryzae pathotypes from infecting wheat; so potential AVR gene mutations leading to new host jumps remain a threat. Indeed, some strains of the closely related Lolium pathotype, causing gray leaf spot of turf grasses, already infect wheat. This review provides the current status of wheat blast research and disease control strategies indicating similarities and differences to rice blast and gray leaf spot. Critical knowledge gaps are discussed.