Wheat blast-An emerging and expanding disease threatening wheat production in tropcal and subtropical regions Abstract uri icon

abstract

  • Wheat blast is caused by Magnaporthe oryzae pathotype Triticum (MoT), a fungus closely related to the rice blast pathogen M. oryzae pathotype Oryza (MoO). The affected areas of this disease had been confined to South America (Brazil, Bolivia, Paraguay and Argentina) after its first occurrence in 1985. However, an outbreak happened in 2016 in Bangladesh, indicating the introduction of wheat blast from South America to South Asia. From 2017 to 2021, this disease kept spreading in Bangladesh despite the unfavorable weather conditions and is now found in 22 districts of the country. The possible further spread of wheat blast in the region poses great threat to wheat production in South Asia. In 2018, wheat blast was reported for the first time in Zambia, indicating its introduction to the African continent. Prediction models based on agro-climatic parameters identified large areas with warm and humid climatic conditions to be vulnerable to this disease, which could further expand with climate change and possible adaptation of MoT to cooler and drier conditions. Strategies to mitigate the effects of wheat blast include the concept of wheat holiday-stop wheat production for a few years in the infected/vulnerable areas, seed treatment, fungicide application, and host resistance. Breeding for WB resistance has been challenged by the very limited source of resistance and the high dynamic potential of MoT populations. Seed treatment is effective against seedling blast but has no effect on spike blast infection. Fungicide application is a preventative rather than remedial strategy, and it has been compromised by the fast emergence of fungicide resistance of MoT. Adjustment of sowing time is the only cultural management method that is widely adopted in WB epidemic regions, and biological control agents are limited and have not been utilized in production. In conclusion, wheat blast is a difficult disease to manage, requiring multi-disciplinary tools and globally synergic actions to mitigate its damaging effects.

publication date

  • September 2022