Friday, December 13, 2013

Bananas and Foc and Taiwan

Part of the old Qing trench network above Keelung city used in the siege of the French.

The world of bananas we see today is not the world that existed sixty years ago. In that world the major export banana was a type called Gros Michel. It was the principal banana imported into the the US until the early 1960s.

And then came the fungus known as Fusarium Wilt, or Foc, also known as Panama disease, where it was first reported back in the 1890s. Over the next half-century Gros Michel was wiped out, with shortages allegedly inspiring the famous "yes we have no bananas" song, according to Wiki. This article observes:
Disaster struck in the mid-1950s when Panama disease turned on the Gros Michel banana. Within a few years, wholesale destruction was seen in plantations in Central America and Africa with 50,000 hectares lost in Honduras alone, said Dr. Molina. This drove the banana business to near bankruptcy and precipitated the move to the relatively less delectable, but resistant, Cavendish banana.

Originating from Southeast Asia, the Cavendish banana replaced the Gros Michel variety on a global scale. Billions of dollars in investments were reportedly spent beginning in the 1960s for the development of infrastructure to accommodate differences in growing and ripening needs of the new variety in different countries. All seemed well with Cavendish as the new banana of commerce until the Fusarium wilt Tropical Race 4 came along (source).
Today Americans and other nations into which bananas are imported consume the resistant Cavendish, which is not as delicious. Unless you have actually been to a banana-raising nation where they raise several varieties, you have probably never tasted a delicious banana.

The first problem of the Cavendish is simple, although it is resistant to some strains (called Races) of Foc, it is horribly vulnerable: all Cavendish bananas today are clones of the first plant, which means they are genetically identical. Which means that any disease that affects one can affect them all. This excellent article on Philippines says:
In the banana business, Foc is conventionally classified into four pathogenic forms known as "Races". Race 1, which destroyed the Gros Michel plantations, also attacks many local cultivars in Asia; Race 2 affects specific cooking bananas; Race 3 attacks Heliconia spp., ornamental plants that are related to bananas; and Race 4 affects a wide range of cultivars, including Cavendish and cultivars susceptible to Race 1 and 2. The extremely virulent strain of Race 4, known as 'Tropical Race 4', is a relatively recent development. Tropical Race 4 has the capacity to affect banana varieties unaffected by other Foc races.
Tropical Race 4 emerged in 1967 in Taiwan, in Chiatung, Pingtung. By the 1990s Taiwan's banana industry was devastated.

The second problem is that Foc is like some nightmare anti-banana biowarfare weapon. Once you have it, there is no economically viable treatment for it. No pesticide, no fungicide, no natural agent. Nada. You can have limited success via intercropping and other approaches, but it can hang out in the soil for decades as a saphrophyte and can travel easily carried by humans, farming machinery, or on banana plant suckers which are symptomless.

The third problem is that banana is a huge crop, third largest fruit crop in the world, and the third largest in Taiwan, with the major cultivation areas being (in order) Pingtung, Nantou, Chiayi, and Kaohsiung. In many countries it enables small growers to earn an income and is a stable source of food. Scary, eh?

The good news is that these small growers with their myriad of cultivars are a precious reservoir of banana biodiversity, since Race 4 doesn't hurt them. It only affects the export bananas, the Cavendish variety, around which the modern banana export industry is built. Scientific American reports:
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.
With the virus appearing in Mozambique and Jordan recently (SciAmer), moving outside Asia, the world banana industry may once again experience an upheaval...
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