Coffee Wilt Disease is caused by a fungus that has led to devastating outbreaks since the 1920s in sub-Saharan Africa, and currently affects two of Africa’s most popular coffee varieties: Arabica and Robusta.
The new research shows that the fungus likely boosted its ability to infect coffee plants by acquiring genes from a closely related fungus, which causes wilt disease on a wide range of crops, including Panama disease in bananas.
[...] The team re-animated cryogenically frozen samples of the fungus that causes Coffee Wilt Disease. There have been two serious outbreaks of the disease, in the 1920s-1950s and between the 1990s-2000s, and it still causes damage. For example, in 2011, 55,000 Robusta coffee trees were killed by wilt in Tanzania, destroying 160T of coffee in the process – equivalent to over 22 million cups of coffee.
[...] In a secure lab at CABI, they re-awakened two strains from the original outbreak, collected in the 1950s and deposited into CABI’s collection, and two strains each from the two coffee-specific fungal strains, with the most recent from 2003. They then sequenced the genomes of the fungi and examined their DNA for evidence of changes that could have helped them infect these specific coffee varieties.
They discovered the newer, variety-specific fungi have larger genomes than the earlier strains, and they identified genes that could have helped the fungi overcome plants’ defences and survive within the plants to trigger disease.
These genes were also found to be highly similar to those found in a different, closely related fungus that affects over 120 different crops, including bananas in sub-Saharan Africa, causing Panama disease, which is currently devastating today’s most popular variety, the Cavendish banana.
While strains of this banana-infecting fungus are known to be able to swap genes, conferring the ability to infect new varieties, the potential transfer of their genes to a different species of fungi has not been seen before. However, the team note that the two species sometimes live in close proximity on the roots of coffee and banana plants, and so it is possible that the coffee fungus gained these advantageous genes from its normally banana-based neighbour.
Coffee and bananas are often grown together, as coffee plants like the shade provided by the taller banana plants. The researchers say their study could suggest not growing crops with closely related diseases together, like banana and coffee, could reduce the possibility of new strains of coffee-killing fungi evolving.
The researchers are now using the re-animated strains to infect coffee plants in the lab, in order to study exactly how the fungus infects the plant, potentially providing other ways to prevent the disease taking hold.
nothing like COVID gain of function research
D. Peck, R. W. Nowell, J. Flood, et al. Historical genomics reveals the evolutionary mechanisms behind multiple outbreaks of the host-specific coffee wilt pathogen Fusarium xylarioides, bioRxiv (DOI: 10.1101/2020.08.07.241695)