Bananas are one of the world’s most widely available fresh fruits. They are particularly popular with children and are a great source of potassium. They come in a peel that serves as their own counter-top storable, easy to open, “biodegradable packaging.” In the US they are typically quite affordable and often serve as “loss leaders” in grocery stores. In the last 50 years the supply of fresh fruit available to American consumers has become more diverse and has increased from 92 to 136 pounds per person per year. Even so, bananas remain the most abundant category at more than 20% of the total (see graph below).
Unfortunately, there is a disease of bananas that has the potential to devastate not only the 12 billion dollar export industry that supplies the “dessert bananas” that are enjoyed by people in more than 100 countries, but also the locally grown cooking bananas and plantains that are important for the food supply in the developing world.
There is a fungus called Fusarium that lives in soil which can kill bananas and plantains. A new strain of that pathogen known as “Fusarium Tropical Race 4” (TR-4) has emerged and in spite of extensive efforts to contain it, TR-4 is slowly spreading throughout the world. Once it contaminates the soil of a given field, that site can no longer be used to grow bananas.
This isn’t the first time that the global banana industry has been threatened by this disease. In the early 20th century what came to be called “Panama Disease” was killing off bananas and disrupting trade. In 1923 there was a hit song titled: “Yes, we have no bananas.” It was released by Frank Silver and Irving Cohn and subsequently recorded by many leading music stars. It was inspired by the way that a certain Greek fruit seller started his answer to every question with “Yes” even when the answer was “No.” It was an awkward way to say that he was unable to stock bananas – probably because of this disease.
By mid-century, it became impossible to keep growing the “Gros Michele” cultivar on which the entire export industry depended. The solution ended up being to switch to a different cultivar called “Cavendish” which happened to be resistant to the disease. Unfortunately now that variety is succumbing to the new, TR-4 race of the same pathogen. The “dessert banana” sector dominated by Cavendish is massive, valuable, and global (see table below). It is a popular fruit for billions of people in 116 countries and it is also the main source of income for millions of people in the 49 countries that generate the exports.
Many observers have questioned why this huge industry is so dependent on a single cultivar of banana, but there are significant practical and economic reasons for this limitation. The reason that bananas can be so affordable is that a finely tuned system has been worked out in which the bananas can be harvested at just the right stage, shipped inexpensively using ocean shipping (with a minimal carbon footprint), and then predictably ripened in facilities close to the points of sale throughout the world. The “back haul” of other goods in those same ships is also key to the economics. There are other banana varieties out there, but they wouldn’t be reliably functional in that system or would require some expensive, carbon-intensive means of transport.
Soon, there will either have to be a replacement or replacements for the Cavendish or the lyric – “yes, we have no bananas” will once again be relevant. Finding those solutions and proving their utility will be very challenging, but not just for the “banana of trade.”
There are also major agricultural communities that are being impacted by this new Fusarium strain as they grow plantains and cooking bananas for local consumption and for another significant export market for those crops (see table below). This isn’t just a “rich world problem.”
The following graphs provide some detail about the extent and distribution of the farming and export industries involved followed by graphs about the major consumer nations.
Where bananas and plantains are grown
The countries that export these crops
The countries that import bananas and plantains
Potential Solutions to the Crisis
The banana industry of the 1950s had the good fortune of finding a workable, disease resistant substitute for the Gros Michele. This time, scientific advancements could allow the development of a more resilient solution based on multiple strategies so that the stage isn’t being set for a next, “TR-5” event. However, each of these comes with its own challenges as summarized in the table below:
There are five potential strategies that could be pursued alone or in various combinations as a means of dealing with the threat of TR-4 in both the export and local banana industries: Chance Mutation, Conventional Breeding, Cisgenics, Genome Editing and Biological Treatments. Those are described below along with some further steps that could make the final system more resilient.
Chance Natural Mutation
In a scenario comparable to the discovery of the disease resistant Cavendish banana in the 1940s, a Swiss/Indian company called Innoterra was able to find some naturally occurring Cavendish (Williams & Grand Nain) mutants that survived the TR-4 in a plantation in the Phillipines. They selected mutants which have a stable sweeter taste profile and adaptive “brix levels” across high and low land production areas. It seems to be very well suited in diverse production areas in the Philippines and it is now being sold as InnoGreen 12 (derived from Williams) and InnoBlac (derived from Grand Nain)” cultivars for South East Asian regions. These lines also exhibit strong quality fruit with no maturity stains or non-browning trait.
Whether these new cultivars could be a solution for the broader export industry that supplies the wealthier countries of the temperate world such as the US depends on a few key factors. The first is that it would need to thrive in other production areas and have the necessary shipping characteristics described earlier which it has proven in Philippines. That finely tuned system also requires sufficient control of another widespread fungal disease of bananas called Black Sigatoka. It only infects leaves, but if it is not controlled it compromises the shipping stability of the fruit. Any new “banana of international commerce” will have to have the yield, quality, shipping profile and other disease management characteristics necessary to make the system work in a highly predictable fashion, and that will have to be evaluated in each growing area. There may also be consumer acceptance issues that need to be evaluated.
Conventional Breeding
Bananas and plantains can be bred, but not starting with the seedless kinds we already know and use. Wild bananas have big, hard seeds and would never be suitable for sale, but as with other fruits it is possible to make “triploids” by crossing lines with 2 of each chromosome (diploids) with tetraploids that have four of each. The offspring have three of each chromosome and are typically seedless. This kind of breeding is being actively pursued by various national and international organizations as a potential solution for the local industries. Ironically even though this means of “genetic modification” involves the most changes in terms of apparent and unknown changes to the crop, it could qualify for the scientifically meaningless “non-GMO” designation that has unfortunate power in the rich world consumer market. Any resistant crosses would have to be extensively evaluated for flavor, shelf-life, shipping potential and pest resistance. Breeding programs of this nature are underway, particularly for the local market segments but timelines for this strategy are long. Modern gene sequencing technology could enable “marker assisted breeding” which can speed up the process.
Cisgenics
Another viable solution to the TR-4 threat to bananas for both rich and poor consumers is to use the tools of modern science to make precision changes a change to the genetics of the existing and well understood cultivars. There are some TR-4 resistance genes have already been identified in various wild bananas and those can be transferred into the genome of any banana or plantain without any changes to all the other highly desirable characteristics needed for its market niche. An academic research lab in Australia led by James Dale has already developed a “cisgenic” TR-4 resistant Cavendish banana using a gene from a wild banana. It has been approved for production in Australia, but for now it is mostly being positioned as a backup plan in anticipation of continued spread of the TR-4 strain throughout the world.
Because it involves putting a banana gene in a banana it is a “cisgenic” rather than a “transgenic” approach. However, because it involves modern science it faces the anti-GMO resistance that persists in spite of decades of documented safety for this approach and has even thus far preventing the utilization of potentially life-saving vitamin A enhanced banana lines in countries like Uganda. Would the brand-sensitive international banana import players be willing to take on the potential pushback by the anti-GMO industry? What about retailers who have hesitated to stock “GMO” products? There have been some encouraging examples. The papaya industry in Hawaii was saved with a transgenic, virus resistant version of that crop. A transgenic, pink pineapple has recently made it to store shelves and a transgenic purple tomato is available to home gardeners. Perhaps the momentum for biotechnology and the looming threat of “no bananas” could be a way to overcome this irrational barrier.
Gene Editing
It is also possible that the genetic clues from naturally resistant banana relatives could guide a “gene editing” approach to confer resistance to the disease without the need to introduce any “foreign” DNA. In the US that wouldn’t require extra regulatory review, but how the EU and even the UK would respond remains ambiguous. Gene editing would also be a way to make a non-browning banana or possibly one with longer “counter-life.”
Integration with Non-Genetic Approaches
There are also some biologicals like BanacXin also developed by Innoterra and chemical products that have been developed which induce other disease resistance mechanisms that exist in all bananas. The new biofungicide BanacXin, is pitched as a ‘two-in-one vaccine’ that can provide farmers a means to control both fusarium tropical race 4 (TR4) and black or yellow sigatoka which has been extensively tested in India and Philippines. Innoterra commenced sales of BanacXin in India & the sales permission for Philippines is being pursued. While there are no chemical fungicides that can control this soil-borne disease, there are biologicals such as Serenade and nematicides such as Velum/Verango that can enhance the overall resistance and and nutrient uptake potential of bananas. These and other biological and chemical approaches could be part of an integrated pest management strategy (IPM) for both Fusarium TR4 and Black Sigatoka.
Conclusions
The bottom line is that there is reason to be hopeful for the future of bananas and the best case is that science and reason prevail in the realm of consumer education and marketing.
Perhaps this threat to both the local and international banana industries could be the impetus to make multiple improvements and get some diversification in the segment. Bananas that are resistant to both Panama Wilt and Black Sigatoka would be highly desirable for the growers. A non-browning trait would reduce food waste during distribution and at the home level. Maybe even more biofortified bananas and plantains could be developed in combination with the disease resistance to further reduce malnutrition and blindness because of vitamin A deficiency. What if bananas could get new color and flavor options like those we have enjoyed with apples and grapes?
Hopefully it will soon be appropriate to write a new song with the chorus, “Yes, we can have bananas!”
