The common banana, a staple of many healthy diets, is on the brink of extinction due to Fusarium wilt of banana (FWB). This is a devastating disease caused by a type of fungal pathogen Fusarium oxysporum f.sp. cubense (Foc) Tropical Race 4 (TR4).
Thanks to an international team of scientists led by the University of Massachusetts Amherst, we now know that Foc TR4 has not evolved from the strain that wiped out commercial banana crops in the 1950s.
Instead, the virulence of this new strain appears to be related to several accessory genes associated with nitric oxide production.
These insights may pave the way for treatments and strategies that can slow, if not control, the uncontrolled spread of Foc TR4.
A tale of two bananas
“The type of banana we eat today is not the same as what your grandparents ate. The old ones, Gros Michel bananas, are functionally extinct, victims of the first Fusarium outbreak in the 1950s,” noted Li-Jun Ma, professor of biochemistry and molecular biology at UMass Amherst and senior author of the paper.
Today, the most popular type of banana available on the market is the Cavendish variety, which was bred as a disease-resistant response to the extinction of the Gros Michel.
For about four decades, the Cavendish banana flourished across the globe in the large monoculture plantations that supply most of the world’s commercial banana crop.
Banana disease and its impact
In the 1990s, the glory days of the Cavendish banana were slowly fading with another outbreak of banana wilt. This outbreak spread rapidly from Southeast Asia to Africa and Central America.
“There was another outbreak of banana wilt,” said lead author Yong Zhang, who completed his PhD in UMass Amherst’s Organismic and Evolutionary Biology program under Ma’s direction. “It spread like wildfire from Southeast Asia to Africa and Central America.”
“We have spent the past 10 years studying this new outbreak of banana wilt,” noted Ma, who is an expert on Fusarium oxysporum, which is not a single species but a “species complex” with hundreds of different varieties that specialize in different influences. plant hosts.
These varieties are defined by the acquisition of strain-specific accessory genes in addition to a common core genome.
“We now know that the TR4 pathogen that destroys Cavendish bananas did not evolve from the race that destroyed Gros Michel bananas,” Ma said.
The TR4 genome contains several accessory genes that are related to the production of nitric oxide, which appears to be a major factor in TR4 virulence.
Strategies to mitigate banana disease
Yong, Ma and their co-authors from China, South Africa and various American universities rigorously sequenced and compared 36 different Foc species from around the world.
The team found that Foc TR4 uses several auxiliary genes for both the production and detoxification of fungal nitric oxide to invade the host.
This key discovery revealed the remarkable impact of nitric oxide production on TR4 virulence, thus providing several strategic avenues to control the spread of this pathogen.
While the team does not yet know exactly how these activities contribute to the disease infecting Cavendish bananas, they were able to determine that the virulence of Foc TR4 was greatly reduced when two genes that control nitric oxide production were eliminated.
“The identification of these accessory gene sequences opens up many strategic avenues to mitigate, or even control, the spread of Foc TR4,” Yong said.
Diversifying the bananas we buy
However, Ma is quick to point out that the ultimate problem threatening our much-loved breakfast fruit is the practice of monoculture.
“When there is no diversity in a large commercial crop, it becomes an easy target for pathogens,” she said. “Next time you’re shopping for bananas, try a few different varieties that may be available at your local grocery store.”
Diversifying the types of bananas we consume can help reduce pressure on the Cavendish variety, making the entire banana industry more resilient.
Supporting biodiversity in banana crops is not just about preserving a favorite fruit; it is about ensuring food security for future generations.
The study is published in the journal Nature Microbiology.
—
Do you like what you read? Subscribe to our newsletter for engaging articles, exclusive content and the latest updates.
Check us out at EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
—
