Banana: cautionary tale of the risk inherent in crop monoculture

Over the past half a century, agriculture systems have become truly global with great benefits in yields and economies of scale.  These benefits, however, have come at the cost of reduced biodiversity resulting in an increased risk from biological and environmental catastrophes.  A relatively small number of key crop species like wheat, corn and soybean, have been established as major staples for diets across the globe along with meat and dairy products.   For those crops that are cultivated, a small number of elite varieties have been deployed on ever-increasing geographic areas.  As more people rely on a small number of crop species and a small number of varieties within these crop species, genetic variation has been limited and agriculture is becoming more vulnerable to major threats like drought, insect pests and diseases.  Such threats are likely to become even worse in many parts of the world as a result of climate change. (BBC news, http://www.bbc.com/news/science-environment-26382067).

source: (wikipedia)

Original native ranges of the ancestors of modern edible bananas. Musa acuminatais shown in green and Musa balbisiana in orange. (source wikipedia)

The global banana crop illustrates this tension inherent in modern agriculture.  Most edible bananas come from primarily two wild progenitors Musa acuminata and Musa balbisiana (http://en.wikipedia.org/wiki/Banana).  Banana consumption divides into two distinct groups:  those that “want” and those that “need”.  (Dan Koeppel, 2007, Banana the Fate of the Fruit That Changed the World).  For those in poorer developing areas of the world that “need”, hard starchy bananas provide more than 20% of daily calories for 400 million people. Total global annual production of bananas exceeds 145 million tonnes with 2/3 of the worlds bananas produced for domestic consumption by smaller farmers.  The major banana producers are: India, Uganda, China, the Philippines, Ecuador, Brazil, Indonesia, Columbia, Cameroon, and Tanzania. For more than 99% of those in richer importing countries who “want”, a single seedless, sexless (sterile), sweet banana variety,

Cavendish is the banana people eat. Four Latin American countries (Ecuador, Costa Rica, Guatemala, Columbia) and the Philippines are the major banana exporters of Cavendish bananas from plantations owned by one of several large companies. The US is a major importer of these bananas. (http://en.wikipedia.org/wiki/Banana).  Europe gets most of its bananas from its former colonies in the Caribbean and Africa. Although wild species of bananas have seeds, crop varieties like the Cavendish do not and are propagated as clones from vegetative plant material.   Thus, the 100 bananas eaten per person per year by consumers in the US are all genetically identical (Dan Koeppel, 2007).  The very uniformity and consistency that drives economies of scale and profitability from deploying plantations of the same genetic material enables the rapid spread of diseases.

Multiple banana varieties. (source wikipedia)

Multiple banana varieties. Cavendish on the right. (source wikipedia)

Although the majority of the bananas consumed globally are not of the Cavendish type, Cavendish bananas have in recent years been introduced as the in more and more countries for export income, even where local bananas serve local markets. Beginning in 1985 the Cavendish crops in Asia began to be destroyed by a wilting disease.  The symptoms observed at that time were reminiscent of Panama disease a fungal disease.  Panama disease caused the extinction of the previous banana industry clone, Gros Michel.  Gros Michel began to be planted in Latin America as a profitable export to the US following the American Civil War, first as a luxury good and quickly developed as a cheap treat for the mass consumer market.

Banana exports grew to large scale during the first half of the 20th century.  Panama disease (first reported in Java) arrived in Central American plantations in the early 1900s, first in Panama (hence the disease name).   It took about 50 years until 1950’s for disease to drive Gros Michel to virtual extinction. During those 50 years, the large banana companies responded to the threat with in an environmentally and socially destructive cycle of abandoning plantations, acquiring land at cheap prices, and clearing more tropical forests to establish new plantations, repeating the cycle over and over for millions of acres in Central America and Columbia.   In addition, companies adopted aggressive pesticide application as a disease management strategy, a strategy that lead to major health consequences for their banana workers.  Companies made profits and were able to provide an inexpensive fruit to the US mass consumer market.  However, company profits were a direct result from land acquisition at cheap prices and low wage.  Both of these business successes were achieved low using questionable corporate practices by today’s standards.

The causative agent for the Panama disease that showed up on Cavendish in the 1980’s has been confirmed to be a new strain of the soil fungus Fusarium oxysporum f. sp. cubense (Foc) like the fungus responsible for the previous epidemic that wiped out Gros Michel.  However,  this new fungal strain, Tropical Race 4 (Foc-TR4)  poses a greater threat to the global banana crop because it is more virulent.  Cavendish was developed as the industry savior in the 1950’s and 1960’s because it was found to resist the first Foc race (race 1) that wiped out Gros Michel.   Unlike race 1, Foc-Tr4 not only infects and kills Cavendish on which it was first observed, it also causes disease on most other banana crops deployed around the world. If Foc-TR4 has not already arrived in Central America, it is only matter of time before it does arrive according to the pathologist who identified the causative agent of both the previous Foc and of Foc-TR4, Tony Poetz (as quoted by Gwynn Guildford, http://qz.com/164029/tropical-race-4-global-banana-industry-is-killing-the-worlds-favorite-fruit/).  Since first observed, Foc-TR4 has spread into Taiwan, Indonesia, Malaysia, the Philippines, China and northern Australia.  As of 2013 the disease had spread to Mozambique and Jordan  (http://www.nature.com/news/fungus-threatens-top-banana-1.14336).

Once in Latin American, with no genetic diversity to resist it, the disease is expected to spread rapidly through the large monoculture plantations of susceptible Cavendish destroying them all in the same way Gros Michel was destroyed by Foc race 1.  In addition, Foc-TR4 is expected to continue destroying banana plantings across Africa, India, Southeast Asia, China, the Philippines, the Malaysian peninsula, Australia, and all the smaller islands where bananas grow.  In fact it is estimated that 85% of the world’s banana crop may succumb to Foc-TR4 (Gwynn Guildford quoted in an interview for NPR’s Marketplace on Mar 6, 2014).

The banana consumers in developed countries eat.  source (wikipedia)

The banana consumers in developed countries eat. (source wikipedia)

Americans and Europeans want bananas and will miss their sweet treat, but of much graver consequence, is the threat to the people who need bananas for their sustenance around the world.  Without a new resistant banana crop, these people face hunger or even starvation, in particular during the “hunger season”, those months after last year’s harvest of the locally grown grain or legumes is depleted and this year’s harvest is not yet mature and ready to harvest. (Guildford, 2014).

Technology if adopted could provide a solution for the future of bananas in Africa and elsewhere. An illustration comes from a response to a different catastrophe, the ethnic bloodshed that spread across Rwanda and Burundi in the 1990’s.  As a result of the violence, millions were left homeless and fled into refugee camps where there was a dire need for food.  Although international aid flowed in for short-term food, a banana research group at the Catholic University of Leuven, Belgium lead by Rony Swennen believed that a longer solution was to introduce new and improved banana plants that they had already developed to combat another devastating disease, Black Sigatoka.   Under Swennen’s leadership, in communication with local farmers, and with the final approval of government officials a collection of  21 “naturally” bred and improved varieties of bananas were planted in trials in Tanzania.  Based on the success of these trials some 2 million of these improved banana plants are in the hands of local farmers.

A combination of traditional breeding and genetic engineering (GMO technology) could produce bananas resistant to FOC-TR4 (Dan Koeppel, 2007).  For the Cavendish variety that has no seeds, and thus cannot be crossed via conventional breeding to create a new resistant variety, genetic engineering offers the only known way to introduce resistance from wild bananas into Cavendish.   Even for bananas that have some seeds, genetic engineering would be a considerably faster method to save these crop varieties.  Genetic engineering could potentially even revive Gros Michel (Butler, Nature 2012).   Groups in various labs including Belgium and Australia have made progress at introducing resistance genes into multiple banana varieties and testing candidate varieties for resistance in field plantings with promising results.  However, it remains unclear whether consumers and governments that have a strong predisposition to oppose genetic engineering are ready to accept such GMO bananas.

What is clear from the history of the banana is the risks inherent in growing a monoculture crop, a single genetic clone of a single crop, over a wide area and over a large number of consecutive years.  Monocultures will be vulnerable to new threats that develop whether these come from biological agents such as diseases or  environmental changes from climate change. At TerViva we take that lesson seriously.  We are developing a suite of elite varieties of a high oil seed tree legume, pongamia.  We intend to deploy such a suite in concert rather than establishing a monoculture of a single high value pongamia variety.  Further, we are working with citrus growers in Florida to introduce pongamia into areas hit hard by citrus greening disease (Huanglongbing).  We view new high value crops such as pongamia as an opportunity for species diversification in agricultural ecosystems and therefore an opportunity to re-introduce genetic diversity.

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For more on the history of the banana and further details of the current banana disease threat see the following sources:

  1. Dan Koeppel (2007):  Banana The Fate of the Fruit That Changed the World. (book)
  2. Gwynn Guillford (2014) “How the global banana industry is killing the world’s favorite fruit”, http://qz.com/164029/tropical-race-4-global-banana-industry-is-killing-the-worlds-favorite-fruit/.

BANANA TIMELINE (modified from Dan Koeppel, 2007)

>5000 BC:  Early banana cultivation in Papua New Guinea (archeological evidence)
 500 BC:  Written record of banana cultivation in India, seedless varieties and vegetative propagation
  650:  Bananas arrive eastern side of Africa, via middle eastern armies and traders . Bananas spreads west to Guinea.
1402:  Portuguese soldiers bring Guinea banana to Canary Islands colony.  Canary Islands export bananas to Europeans today
1826:  Charles Telfair, British naturalist, administrator in Mauritius, collects Cavendish banana and sends back to England
1870:  American Sea captain Lorenzo Baker purchases 160 Bros Michel bananas in Jamaica takes back to US and sells,  sets off “banana craze”
1871-80: Minor Keith, Brooklyn entrepreneur secures Costa Rica contract to build railroads, plants bananas alongside tracks to create business for the trains.
1885:  Captain Baker starts first banana importing company, Boston Fruit grows into United Fruit, current day Chiquita
1894:  US military action in Nicaragua to quell land and labor reforms.  First US military action in Central America on behalf of banana companies.  30 instances of US military actions
1900:  Standard Fruit founded in New Orleans, current day Dole
1903:  First reported case of disease in Panama, named “Panama Disease”
1905:  Honduras becomes largest banana exporter, lasts almost 100 years
1910:  Early banana research lab opened in Costa Rica, some efforts to breed disease resistant bananas
1922:  Panama disease documented in Australia, New Zealand, China, India, and Canary Islands
1935:  Black Sigatoka disease identified in Central America
Panama disease reached devastating levels in Honduras.  Entire towns abandoned.
1946:  United Fruit reaches ownership ~ 1 million acres of land in Cuba, Jamaica, Honduras, Guatemala, Nicaragua, Costa Rica, Panama, and Columbia
1953:  First Cavendish bananas grown by Standard Fruit
1959:  Chiquita sends scientists to Asia on collecting trip to find bananas resistant to Panama disease
1960:  Chiquita opens research program in banana genetics and improvement at La Lima, Honduras.
1961:  Wide-scale adoption of Cavendish banana begins.
1964:  Standard Fruit name change to Dole
1965:  Ecuador surpasses Honduras becomes largest banana exporter, remains largest exporter today
1968: World banana consumption tops 4 billion pounds
1970:  Gros Michel completely replaced by Cavendish
1972:  Black Sigatoka disease (leaf rot fungus) first observed
1978:  Catholic University of Leuven, Belgium founds Laboratory of Tropical Crop Improvement that houses biodiversity International Transit Center, the world’s largest collection of banana with >90,000 samples from 103 countries and 359 locations
1980:  African banana harvest declines, pathogens including Black Sigatoka show resistance to chemical sprays
1981:  Black Sigatoka first observed South America.  Growers expand chemical spraying
1983:  Chiquita closes research facility at La Lima
1985:  Honduras government takes over La Lima and converts it to Honduran Agricultural Research Foundation.
1985-90:  New race of Panama disease causing fungus, Foc-TR4 appears in Asia, destroys Cavendish crops in multiple countries.
1998:  Hurricane Mitch wipes out 80% of Honduran banana industry
1998:  Costa Rica opens world’s largest banana processing plant
           Tony Poetz identifies causative agent to Pananma disease, soil fungus Fusarium oxysporum f. sp. cubense
1999:  US annual consumption reaches 100 bananas/person
2001:  Xanthomonas wilt begins spreading in Africa, incurable, faster moving than Panama disease
2003:  Belgium scientist Rony Swennen leads work to introduce “natural” (not GMO) improved banana (Black Sigatoka disease resistant) to Tanzania, 2 million these improved plants grown today
2006:  Banana research lab opened in Uganda to develop conventional hybrids and bioengineered varieties
2012:  Banana genome sequence determined by international collaboration

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