Rice blast is the most important disease that affects global rice production. Its importance to food security is underlined by the fact that rice contributes 23% of the calories consumed by the global human population and is the most important food product in Asia, where 55% of the world's population lives and 92% of rice is grown and consumed. Population growth has been rapid in the rice-growing regions of the world, creating an increase in demand for rice of 3% per year. Indeed, a recent analysis by the International Food Policy Research Institute indicates that rice production will need to increase 38% by 2030 to feed the expanding human population and will need to be cultivated on less ground as more arable land is lost to housing and industry.
In recent years, rice blast epidemics have occurred in China — where 5.7 million hectares of rice were destroyed between 2001 and 2005 — Korea, Japan, Vietnam and the United States. The need for a better understanding of this disease becomes clear if we consider the poor durability of many blast-resistant cultivars of rice, which have a typical field life of only 2–3 growing seasons before disease resistance is overcome, and increasing energy costs, which affect fungicide and fertilizer prices. Rice blast control strategies that can be deployed as part of an environmentally sustainable plan for increasing the efficiency of cereal cultivation are therefore urgently required.
Researchers in the School of Biosciences at the University of Exeter are studying the devastating rice blast disease, which each year destroys enough rice to feed 60 million people. The disease, caused by a fungus, occurs throughout rice-growing regions of the world and this 'plant pathogen', (known scientifically as Magnaporthe grisea) is the most serious disease of cultivated rice. Therefore knowledge gained about this fungus can be applied to a disease of critical importance to the global food supply.
Exeter researchers were part of the international team which first sequenced the genome of the rice blast fungus in 2006 and they have now used next generation DNA sequencing facilities at Exeter to compare the genomes of isolates of the fungus from around the world. Professor Nick Talbot who leads the research said "We are trying to find out what makes this fungus special in being able to cause such an aggressive disease. By comparing strains with different virulence, we can learn more about the precise genes which allow disease to occur."
The Exeter group have also developed new high throughput methods to study rice blast disease using targeted gene knockouts. This method precisely deletes a single gene from the fungus, allowing its role to be investigated. The research, published recently in Proceedings of the National Academy of Sciences USA, is a major breakthrough in studying the disease process. "By harnessing the power of genomic research, we can rapidly develop a detailed understanding of rice blast disease and use this to guide new strategies for its control" said Professor Talbot.
Exeter's research on rice blast is currently funded by £3 million of grants from the Biotechnology and Biological Sciences Research Council (BBSRC), the agricultural biotechnology industry, development agencies and philanthropic trusts. Of particular importance is the Halpin scholarship programme, supported by an Exeter alumnus, which provides scholarships to young scientists from the developing world to come to Exeter to train in rice blast research.
As well as being an important pathogen, Magnaporthe grisea is also used as a 'model organism' to study the fundamental biology of fungi, many of which cause diseases in both humans and the crops which we rely upon. A research group at the University of Exeter led by Professor Nick Talbot's laboratory has received substantial BBSRC funding to look into rice blast fungus. The group is particularly interested in the mechanisms by which fungal pathogens can infect living host plants, invade their tissues, and cause disease.