The banana, the world's most popular fruit and one of the top food commodities in Southeast Asia, Latin America and Africa, is facing the threat of being wiped out by a virulent strain of fungus, according to researchers from Wageningen University in the Netherlands.
A strain of Fusarium oxysporum - the fungus that causes Panama disease - was found to infect many banana varieties, but the famous Cavendish banana is particularly susceptible to it. The strain, called Tropical Race 4 (TR4), infects the banana through the soil. It enters the roots and interferes the movement of water through the vascular system so that the plant dies.
Additionally, the fungus stays on the contaminated soil for many years and kills all newly planted bananas, rendering large plots of land unsuitable for banana plantation.
In the 1960s, TR4 was reported in Taiwan where it almost completely destroyed the Cavendish banana industry. From there, it spread to other Southeast Asian countries including China, Malaysia, Indonesia and the Philippines. Since 2013, TR4 has been detected in other regions, such as Jordan, Lebanon, Pakistan, Oman and Mozambique. Its most recent detection was in Northern Queensland in Australia.
The fungus has contaminated an estimated 100,000 hectares around the world, and experts predict that it will spread further.
To determine how the disease has spread, the researchers studied DNA samples of the fungus collected from eight countries. They found out that the samples they got from different locations were genetically identical, which means they are clones.
The problem is that Cavendish banana populations have no genetic diversity; they are monocultures, unable to reproduce on their own and evolve. Every new seed planted is also a clone, making it easier for Panama disease to attack.
"This research demonstrates that the quarantine measures and information provided around the globe apparently have not had the desired effect," study author Gert Kema said in a press release.
So what can be done to help stop the spread of TR4 and save the bananas?
"We are gaining more and more insight into the scope of the issue," Kema said. "The ability to quickly identify infected banana plants and infested soils is extremely important in this respect. However, eventually we have to come up with long-term solutions, particularly host resistance, which can only be developed in strong multidisciplinary alliances with various partners and industry."
The study was published online Nov. 19 in the journal PLOS Pathogens.
