Scientists at Wageningen University have demonstrated that the same clone of the Fusarium fungus is infecting Cavendish bananas in several countries dotted across the globe. This shows that this Fusarium clone, also known as Tropical Race 4, is continuing to spread despite the quarantine measures, with disastrous results for banana growers. The results from the research appeared today in the scientific journal PLOS Pathogens. 
 
 Panama disease is caused by the Fusarium oxysporum f.sp. cubense fungus. One of the Fusarium strains is called 'Tropical Race 4' (TR4) and infects many local banana varieties as well as the widely exported Cavendish banana, which is very susceptible to this strain. The soil-borne fungus enters the banana plant through the root and eventually kills the entire plant. Banana-growing plots infested with the fungus remain contaminated for many years. It is then no longer possible to cultivate bananas on such a plot of land, as new banana plants become infected too. Large areas of banana plantations in countries such as Jordan, Mozambique, China, the Philippines, Pakistan and Australia are no longer suitable for banana farming, as they have become infested with the Panama disease fungus. There are currently no means of combating the disease; only quarantine measures can prevent banana plantations from becoming infested. 
 
 DNA investigation 
 
 The researchers at Wageningen UR analysed the DNA of many fungus specimens from eight countries where the fungus has recently been identified, including Jordan, Lebanon and Pakistan, in order to trace how Panama disease has come to spread to different locations across the globe. The research highlighted that the strains of the fungus, which were collected are genetically identical. The strains are clones. Gert Kema, banana expert at Wageningen UR, says: 'This research demonstrates that the quarantine measures and information provided around the globe apparently have not had the desired effect.' 
 
 A tale of two clones 
 
 Not only the TR4 fungus strain is a clone: all Cavendish bananas also share the same genes. Kema explains: 'The Cavendish banana is very susceptible to TR4. Therefore, the fungus can spread easily due to the worldwide monoculture of Cavendish bananas. That's why we have to intensify awareness campaigns to reach small and large-scale growers in order to help them with developing and implementing quarantine measures preventing the fungus from continued spreading.' 
 
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 Worldwide approach needed to stop further spreading 
 
 To stop further spreading, Kema's team is working with a large number of partners in different locations across the globe to develop short-term solutions for Panama disease management. Kema continues: 'We are gaining more and more insight into the scope of the issue. 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.' 
 
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 Explore further: Panama disease detected in banana plantations in Pakistan and Lebanon 
 
 More information: Nadia Ordonez et al. Worse Comes to Worst: Bananas and Panama Disease—When Plant and Pathogen Clones Meet, PLOS Pathogens (2015). DOI: 10.1371/journal.ppat.1005197 ||||| Sanjit Das/Bloomberg via GETTY IMAGES 
 
 A variant of a fungus that rots and kills the main variety of export banana has been found in plantations in Mozambique and Jordan, raising fears that it could spread to major producers and decimate supplies. The pathogen, which was until now limited to parts of Asia and a region of Australia, has a particularly devastating effect on the popular Cavendish cultivar, which accounts for almost all of the multibillion-dollar banana export trade. Expansion of the disease worldwide could be disastrous, say researchers. 
 
 The disease is caused by strains of a soil fungus called Fusarium oxysporum f. sp.cubense (Foc). A strain of Foc previously wiped out the Gros Michel cultivar, which was the main exported banana variety from the nineteenth century until the 1950s. In response, the industry replaced Gros Michel plants with the Cavendish variety, which is resistant to that Foc strain. But Cavendish is susceptible to the new Foc Tropical Race 4 (Foc-TR4) strain, and could meet the same fate as Gros Michel if the fungus reaches Latin America, the world’s leading banana exporter, says Rony Swennen of the Catholic University of Leuven in Belgium, and a banana breeder at the International Institute of Tropical Agriculture in Dar es Salaam. “It’s a gigantic problem,” he adds. Although Foc strains spread slowly, they are almost impossible to eliminate from soil. 
 
 Foc-TR4 was first detected in Asia in the 1990s, and is now found in Taiwan, Indonesia, Malaysia, the Philippines, China and northern Australia (see ‘Fruit threat’). The outbreak in Jordan, reported on 29 October (F. A. Garcia et al. Plant Dis. http://doi.org/qd3; 2013), was the first to be described outside those nations. The Mozambique outbreak was reported last month. 
 
 Nobody is sure how the fungus arrived in Jordan or Mozambique. Migrant workers from Asia might inadvertently have brought contaminated soil with them. Another possibility is the import of infected rhizomes — the stems from which banana plants propagate. But much of the Cavendish industry now uses tissue culture, which produces pathogen-free plantlets. 
 
 Source: FAO 
 
 To slow the spread, good farm hygiene, and prompt quarantine and destruction of infected plants are crucial. Altus Viljoen, a researcher at Stellenbosch University in South Africa, was called in to identify the cause of the Mozambique outbreak, and says that authorities were quick to take action. He estimates that the disease has been present for two to three years. 
 
 Gert Kema, a Fusarium researcher at Wageningen University and Research Centre in the Netherlands and co-author of the Jordan report, believes that further spread is inevitable. “I’m incredibly concerned,” he says. “I will not be surprised if it pops up in Latin America in the near future.” That region, along with the Caribbean, accounts for more than 80% of banana exports. If Foc-TR4 takes root there, it could lead to the slow demise of industrial farming of the Cavendish variety. 
 
 Smaller farms in Asia are already trying to mitigate losses. Tissue culture of Cavendish plants has generated variants with random mutations that confer partial resistance to Foc-TR4. Planting of these variants, in combination with measures such as crop rotation, has allowed the cultivation of bananas on contaminated land. But production losses and higher costs make affected plantations less economically viable. 
 
 Progress in creating bananas fully resistant to Foc-TR4, either by classical breeding or genetic engineering, has so far been limited. The wild Asian banana Musa acuminata malaccensis— the genome of which was published last year (A. D’Hont Nature 488, 213–217; 2012) — seems to be resistant, and researchers are experimenting with putting its resistance genes into the Cavendish. The resulting transgenic specimens have been in field trials for 18 months on contaminated ground in Australia, and are looking “very promising”, says James Dale, director of the Centre for Tropical Crops and Biocommodities at Queensland University of Technology in Brisbane, Australia. But he cautions that the full results are not yet in. 
 
 For those who buy their bananas in supermarkets, the Cavendish may well be the only variety they know. But exports of the cultivar account for only about 13% of the 150 million or so tonnes of bananas and cooking bananas (plantains) produced annually. Industrial farms growing a single Cavendish cultivar are at a high risk of Foc-TR4 infestation, but the fungus poses less of a threat to the bulk of the bananas that provide a staple for some 400 million people worldwide. 
 
 Most of the bananas important for the food supply are grown by smallholder farmers in low-income countries and consumed locally. Hundreds of cultivars are farmed, and this biodiversity is an important rampart against disease. Researchers do not yet have a full picture of the susceptibility of these varieties, but many cultivars are likely to be resistant to Foc-TR4 because they are biologically different to the Cavendish. 
 
 For his part, Dale is trying to engineer Gros Michel bananas for resistance to the original Foc strain. The Cavendish is bland by comparison and it bruises more easily. Dale would like to see Gros Michel on supermarket shelves again. “It’s such a superior banana to Cavendish. To bring it back would be wonderful.”
– If you like bananas, it's time to start savoring them while you still can. A deadly fungus that's been killing the plant since the 1960s has jumped continents, moving from where it ravaged crops for decades in Southeast Asia to parts of South Asia, Australia, the Middle East, and Africa—and that's just since 2013, reports Quartz. The so-called "Panama" disease is spreading thanks to a single clone of the Fusarium fungus, also called Tropical Race 4, scientists report in the journal PLOS Pathogens. Worse still, one of the world's most popular bananas, the Cavendish, is particularly susceptible to this strain. The soil-borne fungus travels up the plant's roots, ultimately killing the plant and infesting entire banana plots, which are then contaminated for years. Entire swaths of banana plantations in Australia, China, the Philippines, Jordan, Mozambique, Pakistan, and beyond have been infested in the past two years, putting many farmers and families out of business and cutting them off from a major food source, reports PhysOrg. Right now the only way to fight the disease is through strict quarantine, so researchers are trying to spread the word about effective measures in the hopes of getting a step ahead of the fast-spreading fungus before it hits Latin America, where most of the world's bananas are grown. Once it lands there, notes Quartz, "the days of the iconic yellow fruit are numbered." (Some researchers hope it's possible to genetically modify bananas to resist the fungus.)