ABSTRACT
The blast-causing pathogen has a wide host range including wheat on which it is caused by Magnaporthe oryzae pathotype Triticum. Although wheat blast is mainly a spike disease and phenotyping protocols are still evolving, its symptoms also appear on all aerial parts. Wheat blast can be catastrophic, causing up to 100% yield loss. First sighted in Brazil in 1985, it quickly spread to several other South American countries. The first appearance of wheat blast in Asia was reported from Bangladesh in 2016. Such migratory capabilities of the pathogen could jeopardise the food security of 300 million inhabitants of South Asia. The high genetic-pathotypic variability observed in the pathogen is also responsible for the low durability of the host resistance and may also be accelerating host shift by the pathogen. This variability also causes fungicide resistance and necessitates the search for new fungicides and new resistance sources with novel genes. The disease can spread through seed and survive on crop residues and the infected rachis passes the pathogen to harvested seed. Growing susceptible cultivars over large areas coupled with favourable climatic conditions viz., concurrent heat and humidity, can lead to widespread heavy losses. The pathogen propagules have been reported to travel up to 1000 m from the inoculum source. The fact that, at best, fungicides offer partial control and that the pathogen is fast-evolving and adapting to non-traditional areas, only adds to the potential damage of this killer disease. The disease requires an integrated management strategy, including quarantine, chemical control, wheat holidays, cultural practices, genetic resistance, biological control and forecasting, as no single approach offers full protection.
