Imma Perfetto
Cosmos science journalist
New research reveals the fungal pathogen devastating commercial banana crops around the world did not evolve from the strain that wiped out Gros Michel bananas in the 1950s.
Virulence of the new strain, Fusarium oxysporum f.sp. cubense (Foc) tropical race 4 (TR4), seems to be driven by genes associated with the production and detoxification of nitric oxide.
The study appears in Nature Microbiology.
“The kind of banana we eat today is not the same as the one your grandparents ate,” says Li-Jun Ma, professor of biochemistry and molecular biology at the University of Massachusetts Amherst, US, and the paper’s senior author.
“Those old ones, the Gros Michel bananas, are functionally extinct, victims of the first Fusarium outbreak in the 1950s.”
Gros Michel were replaced with the Cavendish variety, which remains the most popular commercially available banana today. But, since the outbreak of TR4 in 1990s, scientists have been working tirelessly to prevent history from repeating itself.
Ma and colleagues sequenced and compared 36 different Foc strains collected around the globe. They determined that TR4 uses accessory genes associated with fungal nitric oxide to invade its banana host.
They could greatly reduce the virulence of Foc TR4 by knocking out 2 genes that control nitric oxide production.
“Identifying these accessory genetic sequences opens up many strategic avenues to mitigate, or even control, the spread of Foc TR4,” says Ma.
However, to Ma, the ultimate problem facing bananas is the practice of monocropping.
“When there’s no diversity in a huge commercial crop, it becomes an easy target for pathogens,” she says.
“Next time you’re shopping for bananas, try some different varieties that might be available in your local specialty foods store.”
