Source: The National Science Foundation

Researchers have sequenced the genome of rice blast fungus, providing them with key information to tackle the devastating rice blast disease. The genetic blueprint of more than 11,000 genes of Magnaporthe grisea--the culprit pathogen--will allow researchers to study host-pathogen interactions of this disease at the molecular level, leading to new ways to defeat the fungus.

Rice blast disease currently devastates rice yields, destroying enough grain to feed 60 million people. For decades, growers around the world have worked to control the disease with costly fungicides. To date, the fungus--through its ability to mutate and better attack plants--has beaten both chemical treatments and genetic resistance developed by plant breeders in some types of rice. A strategy to eliminate the disease would increase world rice production by more than 10 percent.

North Carolina State University researcher Ralph Dean and his colleagues published this sequencing work in the April 21 issue of Nature. The research marks the completion of the first draft sequence of a plant pathogen.

By combining the genetic information of the pathogen with the previously published rice genome, scientists will have new insight into the molecular mechanisms by which the fungus infects plants and adapts to thwart the host's defenses. Additionally, the knowledge gained from studying rice blast disease will benefit other investigations focused on the molecular mechanisms of plant-microbe interactions. For example, it is now known that this fungus uses a new class of receptor to distinguish rice from all other plants.

As Dean said, "Decoding the rice blast genome is a great achievement which couldn't have come at a better time. Rice is the primary source of nutrition for much of the world, particularly Southeast Asia. Following the devastating tsunami, every effort will be needed to improve rice production, and in the long-term, having the genome sequences of both rice and rice blast will greatly aid in this effort."

Dean's work was supported in part by the National Science Foundation's (NSF) Microbial Genome Sequencing Program. A joint effort between NSF and the United States Department of Agriculture (USDA), the program funds genome sequencing projects of importance to the nation's food and fiber supply.

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of nearly $5.47 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives about 40,000 competitive requests for funding, and makes about 11,000 new funding awards. The NSF also awards over $200 million in professional and service contracts yearly.

April 20, 2005

Related news release from Nature

Researchers have sequenced the genome of the world's most devastating rice fungus, opening the door to the development of crops that can resist infection.

The fungus, called Magnaporthe grisea, is responsible for rice blast, a disease that destroys enough rice to feed 60 million people each year. "That's a very conservative estimate," says plant pathologist Ralph Dean, who has studied the fungus for more than a decade at North Carolina State University in Raleigh. The fungus particularly affects rice in hot and humid countries such as Thailand and the Philippines.

With the pathogen's global impact in mind, Dean and his colleagues set their sights on obtaining the genetic sequence of the rice-blast fungus seven years ago. In combination with the DNA sequence of rice itself, which researchers established in 2002, the team hopes the code will facilitate the development of genetically modified rice capable of resisting the disease.

"I equate this to a battlefield. The key to any battle is to understand the strength and weaknesses of your enemy," Dean explains.

Spore war

Using standard laboratory techniques for genome sequencing, the team determined that the rice-blast fungus has more than 11,000 genes. The work, reported in Nature¹, marks the completion of the first draft sequence of a plant pathogen.

Importantly, the code reveals that M. grisea uses a new class of receptor to distinguish its target, rice, from other crops. These receptors are found on the infectious spores of the fungus, which can aggressively punch into the leaves of rice plants.

Related news

A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

April 18, 2005
Source: The Standard, Hong Kong , 21 Apr 2005 [edited]


Rice menace surrenders gene secrets

Scientists have unraveled the genome of the rice plant's greatest fungal menace, a harvest-wrecking foe that each year destroys the potential to feed 60 million people.

_Magnaporthe grisea_ is the 1st disease-causing plant fungus to have its genetic code unraveled. Researchers hope it will open the way to newer, smarter and less damaging weapons against the menace.

Also called rice blast, [RB] the fungal pathogen _M. grisea_ [Mg], spores germinate on rice leaves, colonizes the leaf, producing grayish spindle-shaped lesions from which more spores emerge. Aided by rain or dew, young infected seedlings are often destroyed; in older plants, the grain is lost.

"RB is one of the most destructive diseases of rice because of its wide distribution and its destructiveness," according to the Manila-based International Rice Research Institute. In India, more than 266 000 tonnes
of rice are lost each year, about 0.8 per cent of total yield. In Japan, about 865 000 hectares of rice are at risk and in the Philippines many thousands of hectares suffer more than 50 per cent yield losses. Mg strains attack 50 other kinds of grasses, including wheat, barley, and millet.

The fungal genome, published today in Nature (21 Apr 2005. Dean RA, et al. Nature 2005; 434: 980-6.
Abstract:
<http://www.nature.com/nature/journal/v434/n7036/abs/nature03449.html>, 
news item <http://www.nature.com/news/2005/050418/full/050418-9.html>)  
suggests the organism has 11 109 genes -- similar to other fungi that have been sequenced. Mg is believed to be able to secrete 739 proteins -- twice as many as in other sequenced fungal genomes -- in order to penetrate and infect its host. 8 genes alone are used to synthesize cuticle-degrading enzymes called methyl esterases that aid in disease expression. By identifying the genes of crop pathogens and seeing how they work, scientists can target ways of blocking them chemically or of breeding plants that are resistant to the invader. Ideally, these solutions will be cheaper and environmentally safer than spraying with expensive pesticides.

--
ProMED-mail <promed@promedmail.org>

[Worldwide, RB disease is one of the most devastating diseases of rice, the staple food for 2/3 of humanity. Crop losses associated with RB have been magnified in recent times due to intensification of rice production.
Genetic resistance continues to be the major means of disease management for RB, but Mg is able to overcome this resistance rapidly. A gene has been isolated that controls cultivar-specificity of Mg with rice and has been
identified with the corresponding disease resistance gene.

Disease management involves several options, including manipulation of planting time and fertilizer and water management, early rather than late sowing of seeds after onset of the rainy season, avoidance of excessive fertilizer, especially nitrogen, which increases RB incidence, and water management practices in rainfed areas to lessen the likelihood of stress, which also aids RB control.

Planting resistant varieties against RB is the most practical and economical way of controlling the disease and, if necessary, systemic fungicides such as pyroquilon and tricyclazone are possible chemicals for controlling the disease.

Links:
<http://www.plantpath.wisc.edu/pdru/Leong/rice_project.html>
<http://nar.oupjournals.org/cgi/content/full/30/1/121>
<http://www.knowledgebank.irri.org/riceDoctor_MX/Fact_Sheets/Diseases/Rice_Blast.htm> 
<http://bk.snu.ac.kr/bk21/english/topic_7.htm>
- Mod.DH]