The banana plants that produce the most popular variety of fruit in the world have been temporarily made resistant to a fungal disease that is spreading across the globe and destroying plantations. This work is likely to lead to permanent resistance in bananas.
“The question that we need to ask is: Can this mechanism be continuously triggered?” asks Gertkema from Wageningen University in the Netherlands. “We need more information about it.”
In the past, the main banana variety exported to Western countries was called Gros Michel. In the 1920s, a strain of Fusarium called Tropical Race 1 caused Panama disease and decimated banana plantations. In the late 1950s, banana growers switched to the Cavendish, which was not as tasty as Gros Michel but highly resistant to TR1.
Another strain of Fusarium, called TR4, that kills many varieties, including Cavendish, is spreading into more countries. This fungus threatens food security and livelihoods in many places.
Kema, along with his colleagues, wondered if exposure of Cavendish bananas to TR1 could protect them from TR4. The team dunked young plants in a solution that contained various types of TR1 fungus. The team immersed the plants at different intervals, from 30 minutes up to 10 days afterward.
The team discovered that exposure to a specific strain of TR1 in Brazil could provide significant protection from TR4 for up to 10 days later.
Kema says, “Somehow you’re turning on a protection mechanism that protects TR4 plants as well.” “But this protection is temporary.”
He says that this protective effect was found in plants of other species. Because plants don’t have immune system cells that can remember pathogens like animals do. The product comes from switching on general protective mechanisms instead of specific ones that are a result of a vaccination. The team is trying to figure out how to permanently activate these mechanisms without exposing bananas to live fungal diseases.
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Kema says that even if this could be done or other approaches, such as genetics engineering, it would not solve the entire industry’s problem, especially because TR4 isn’t the only disease affecting the banana industry.
He says the main problem is that the world relies heavily on one variety of fruit. Cavendish bananas account for 95 percent of all exports and more than half of the total banana crop. All Cavendish bananas have the same genetic makeup because Cavendish is like most edible bananas. This makes the plantations more susceptible to disease.
Kema says that diversification is essential. The banana industry must invest in the development of new varieties that are tasty and resistant to disease. Supermarkets should stock them, and customers need to purchase them. Kema says that banana production is not sustainable at the moment.