Researchers have recovered specimens of fungi that cause coffee to wither to find out how the disease evolved and how it could be prevented.
Coffee wilt is caused by a fungus that has led to devastating outbreaks in sub-Saharan Africa in the 1920s and currently affects two of Africa’s most popular varieties of coffee: Arabica and Robusta.
“If we can understand how new types of disease develop, we can give producers the knowledge they need to reduce the risk of new diseases.” Lily Peck
New research shows that the fungus may have increased its ability to infect coffee plants by acquiring genes from a closely related fungus that causes wilting disease in a wide range of crops, including Panama disease in bananas.
Researchers say this knowledge can help farmers reduce the risk of new strains of disease, for example by not planting coffee with other crops or by preventing the accumulation of plant debris that can shelter related fungi.
The research team from Imperial College London,, University of Oxford, and the agricultural non-profit CABI, also say that studying historical samples in the CABI crop collection can provide a wealth of information on the development of crop diseases and find new, sustainable ways to control them. The study was published today in BMC Genomics.
The study’s first author, Lily Peck, studied science and partnership solutions for doctoral students on the changing planet at the Grantham Institute and the Imperial Department of Life Sciences. She said: “The use of increasing amounts of chemicals and fungicides to control emerging crop diseases is neither sustainable nor affordable for many growers.
“If we can instead understand how new types of disease develop, we can give manufacturers the knowledge they need to reduce the risk of new diseases in the first place.”
The team re-animated the cryogenic frozen samples of the fungus causing coffee wilting disease. There are two serious outbreaks of the disease, in the 1920s and 1950s and between the 1990s and 2000s, and it still causes damage.
For example, in 2011, 55,000 Robusta coffee trees were killed by wilting in Tanzania, destroying 160T of coffee in the process – the equivalent of more than 22 million cups of coffee.
In the epidemic that began in the 1920s, Coffee Fading disease infected a wide range of coffee varieties and was eventually brought under control in the 1950s through management practices such as burning infected trees, searching of natural resistance in coffee and breeding programs selected for more resistant plant varieties.
However, the disease reappeared in the 1970s and spread widely in the 1990s and 2000s. Two separate populations of diseases have been identified, each infecting only certain types of coffee: one infects Arabica coffee in Ethiopia and the other Robusta coffee in East and Central Africa. The team wanted to study how the two strains came to be.
In a secure laboratory at CABI, they reawakened two strains from the original outbreak, collected in the 1950s and deposited in the CABI collection, and two strains from the two coffee-specific fungal strains, the last of which sequenced the genomes in 2003. of mushrooms and examines them DNA for evidence of changes that could help them infect these specific varieties of coffee.
They found that newer, variety-specific fungi had larger genomes than earlier strains and identified genes that could help fungi overcome plant protection and survive in plants to cause disease.
These genes have also been found to be very similar to those found in a different, closely related fungus that affects more than 120 different crops, including bananas in sub-Saharan Africa, causing a disease in Panama that is currently ravaging today’s most popular variety, the banana. Cavendish.
While strains of this infectious banana fungus are known to alter genes, giving the ability to infect new varieties, the potential transfer of their genes to different types of fungi has not been seen before.
However, the team notes that both species sometimes live in close proximity to the roots of coffee and banana plants, so it is possible that the coffee mushroom acquired these beneficial genes from its usual banana neighbor.
Coffee and bananas are often grown together, as coffee plants like the shade provided by taller banana plants. Researchers say their study may suggest that not growing crops with closely related diseases, such as banana and coffee, could reduce the chance of developing new strains of fungi that kill coffee.
The evolution of outbreaks
Researchers are now reusing animated strains to infect coffee plants in the lab to study exactly how the fungus infects the plant, potentially providing other ways to prevent the disease.
“Our goal is to repeat this study for many plant pathogens, eventually producing a ‘rule book’ for the development of pathogenicity, which helps us prevent future outbreaks where possible.” Professor Timothy Baracle
Insights can also be applied to a variety of cultivated plants, where other closely related plant pathogens can make similar leaps, causing new diseases. After showing the value of the study of historical specimens of plant diseases, the team plans to repeat the study with other diseases stored in the CABI collection, which contains 30,000 specimens collected from around the world over the past 100 years.
Lead researcher Professor Timothy Baracle of the Department of Zoology at Oxford and the Department of Life Sciences at Imperial said: “The historical approach shows us what happens to a plant pathogen before and after a new outbreak. We can then study the mechanisms of evolution and improve predictions of how such outbreaks may occur in the future.
“Our goal is to replicate this study for many plant pathogens, eventually producing a ‘rule book’ for the development of pathogenicity that helps us prevent future outbreaks where possible.”
Reference: “Historical Genomics Reveals the Evolutionary Mechanisms Behind Multiple Outbreaks of Host-Specific Pathogen Fusarium Xylarioides” by Lily D. Peck, Reuben W. Nowell, Julie Flood, Matthew R. Ryan, and Timothy G. Barraclough, June 4, 2021 Mr. BMC Genomics.
DOI: 10.1186 / s12864-021-07700-4