A Reason to Go Bananas? The Possible Extinction of the Cavendish

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Biology 103
2005 Final Paper
On Serendip

A Reason to Go Bananas? The Possible Extinction of the Cavendish

Zachary Grunau

The banana is by many accounts the world's most popular fruit. Despite its American connotation as a sweet, dessert-style fruit, the banana is a complicated and important food that comes in many varieties. Recently, in popular science magazines especially, there has been somewhat of a "banana scare." Some scientists have predicted that the popular Cavendish banana, which serves as the poster-banana for Americans, is going to be extinct in 10 years, with no replacement readily available((1)). This web paper will focus on the current debate surrounding the fate of the Cavendish banana.

The word "banana" is a general term that covers a large variety of species and hybrids in genus Musa of the family Musaceae. The word also is used for the fruit of the plant, which is technically a false berry. ((2)) Banana plants are not trees but rather herbs, with a stem that resembles a tree trunk. ((2)) Suckers grow out from the main plant, and it is on these suckers that the fruit clumps form. The eldest sucker replaces the main plant when the main plant dies. In this way, banana plants are able to reproduce indefinitely without genetic variation, as though the plant never really dies. ((2))

This fact concerning bananas is especially important in understanding the current "threat" to the Cavendish variety of banana. First, some information on the Cavendish: Cavendish bananas are the standard banana for much of the world. They are yellow, elongated tubes containing a sweet fleshy fruit which can be eaten raw (many banana types and plantains must be cooked before being consumed.) The Cavendish was first found in Southeast Asia and brought over to the Caribbean in the early 20th century, being put into commercial production soon after. ((1)) The average American eats 26.2 pounds of Cavendish bananas every year and 100 billion total Cavendish bananas are consumed every year. ((3)) Every one of these fruits is identical, at least genetically, to its brothers and sisters. The Cavendish banana plant does not reproduce by mixing genes, but rather through the method of removing suckers and replanting them. Essentially, every Cavendish banana in the world is a the same plant brought over to the Caribbean earlier this century. ((3)) The plant has no other means to reproduce; each fruit produced is 100% sterile. ((1))

Clearly, this can be a problem. As anyone with a basic understanding of the theory of natural selection understands, genetic diversity is the basis for the survival of any living organism. A series of clones, continuing on in an unchanging existence, will not be prepared for the onslaught of various challenges nature sets to her creations. That is why banana farmers are concerned for the Cavendish's future. Ironically, the Cavendish was adopted as the banana of choice because of a genetic strength: its resistance to Panama disease, or Banana Wilt, which devastated crops of an earlier world favorite, the 'Gros Michel." ((4)) This does not mean, however, that Cavendish bananas are resistant to the many other pests and diseases that threaten banana production all over the world every day.

Cavendish bananas are already under attack from the 'Black Sigtoka' fungus, but farmers are able to control the threat with constant pesticide sprayings. ((4)) This process is expensive and inefficient, but effective. There has been recent talk of a greater threat: a new version of the Panama disease, known as "race-4," which the Cavendish are particularly susceptible. Race-4 is such a threat because it is a soil-bound fungus resistant to all known fungicides. ((3)) Most of the bananas that reach American shores are grown in Latin America, which has not yet felt the effects of Race-4—which is why many are concerned that it is only a matter of time before the fungus finds its way to the New World. ((5)) News articles quoting scientists have predicted that we will lose the Cavendish within 5-10 years.

However, there is hope. After the initial swell of concern for the Cavendish, other scientists spoke out, claiming that, while we should be concerned for the Cavendish's future, all is not lost. The UN's Food and Agriculture Organization, responding to the media's attention to the issue, advised that growers increase genetic mixing of the hundreds of other forms of bananas in order to prevent any kind of widespread extinction. ((2))((6)) The FAO claimed that the many small-scale farmers growing other varieties of bananas that are not threatened by many of the diseases threatening the Cavendish will be integral in providing the bananas capable of replacing the Cavendish if the many threats, most notably race-4, wipe it out. As long as growers remain aware of the dangers in the mass-production of genetically non-diverse fruit from now on, says the FAO, we will not run into a problem on a crisis-level.((6)) Other scientists claim that even if race-4 were to spread to Latin America, it could be controlled through highly advanced measures of containment and plantation placement. ((7))

Though some organizations, like the INIBAP (The International Network for the Improvement of the Banana and Plantain), are claiming that not enough work is being done to ensure the future of the banana as the 4th most economically important fruit source in the world, scientists are working towards solutions to these problems. ((8)) Some, like the FAO suggests, are working with the hundreds of other kinds of bananas to find a hybrid replacement. Others are working with the Cavendish and attempting to use biotechnology to manipulate the genetics of the Cavendish in order to produce a more disease resistant fruit. ((1)) Will the Cavendish suffer the same fate as the 'Gros Michel' did in the 1960's? The answer, it appears, is not important, as long as the world is open to some change. While efforts have not produced that 'perfect' banana, there are many promising beginnings, such as a sweet banana resistant to Black Sigatoka, thanks to some genetic material from radishes. ((1)) Variety, in any case, is a good thing. We may lose the Cavendish, but the banana will go on.

1) Article in Popular science
2)Banana Information Page 3)Wikipedia's entry on bananas
4) Biotech's article on Extinction
5) Article on the debate of the issuea at prweb
6) FAO Release 7)Article on debate at eurekalert
8)The INIBAP's Homepage

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