Early last century, the Fusarium fungus, causative agent of Panama disease, eliminated the Gros Michel banana variety. Farmers then opted for the resistant Cavendish banana, but now a new Fusarium strain, TR4, is threatening this very popular banana variety too. Colombian and Wageningen researchers may have found a solution. Treatment with a non-virulent Fusarium strain stops the disease symptoms, they write in PLOS ONE.
Using a non-virulent, i.e. non-pathogenic, variant of a pathogen to combat plant diseases is a well-known strategy. This led PhD student Fernando García-Bastidas and his supervisor Gert Kema of Wageningen University to the idea of testing this approach in bananas as well. They combined several non-virulent Fusarium strains with the pathogenic TR4 strain (Tropical Race 4). ‘And for the combination Race 1 and TR4, the results were fantastic,’ says García-Bastidas. Cavendish banana plants first treated with the non-pathogenic Race 1 strain showed much less disease symptoms after infection with TR4 than untreated plants.
Gene transfer
‘Unfortunately, Race 1 is also still a pathogen,’ says García-Bastidas. This strain does affect many other banana varieties and so cannot be used without restriction. ‘In addition, we know from Fusarium that horizontal gene transfer is possible in this asexual fungus,’ says Frank Takken, Fusarium researcher at the University of Amsterdam who was not involved in the study. ‘So you could possibly make the pathogenic TR4 strains even more pathogenic with this.’
Still, both researchers find the results hopeful. ‘Gene expression analysis confirmed that results did not come from competition or hostility between the two Fusarium strains,’ García-Bastidas explains. Instead, the results suggest that infection with Race 1 activates the defence mechanism of the banana plant. A subsequent TR4 infection thus has no chance.
Trigger
This very insight gives the researchers hope that they can find another way to activate the defence mechanism against TR4. Here, so-called trigger molecules play a crucial role; they recognise the pathogen and put the defence into action. Currently, it is still unknown what the trigger is for Race 1. The researchers in García-Bastidas’s team are working hard to find new leads to protect banana plants.
F.A. García-Bastidas, et al, ‘Induced resistance to Fusarium wilt of banana caused by Tropical Race 4 in Cavendish cv Grand Naine bananas after challenging with avirulent Fusarium spp.’ PLOS ONE (2022) (Open Access)
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