May 1st, 2019

Bananas, Panama Disease, and the Irish Potato Famine

In 1845, a water mold known as “late blight,” decimated Irish potato fields. At the time, largely due to an injustice of land distribution, about one-third of Ireland’s population was completely dependent on a single variety of potato, the “Irish Lumper,” for food calories. The disease wiped out half the Lumper crop in the first year and almost 75% of the harvest over the next seven years. The rapid destruction of the nation’s most important food crop led to the deaths of one million Irish men and women, forcing nearly as many to abandon their homeland as refugees. Just over a hundred years after The Great Famine, Panama Disease caused the world’s bananas to follow suite.

Bananas, Panama Disease, and the Lesson of the “Irish Potato Famine”

Before we get there, first, some quick banana biology. Similar to potatoes, bananas are not grown from seed. Potatoes can produce seed, but the seeds do not grow true to type. Saving and planting potato seed is like planting apple seeds, you might grow something new and wonderful, but you are far more likely to grow something strange and unusable. However, unlike potatoes and apples (grown from tubers and cuttings), the reason we don’t grow bananas from seed is because they no longer produce them.

The Cavendish bananas we find in groceries throughout the world are the result of crossing a tetraploid banana (which has four copies of every chromosome instead of two) with a normal diploid banana. The finished product: consistently triploid bananas that are incapable of producing seed. The reality of this genetic anomaly is that nearly every exported banana in the world is a genetic clone vegetatively propagated by planting bits and suckers or via lab-controlled tissue culture.

Prior to 1965, the Gros Michel was the world’s export banana. Compared to today’s Cavendish, it had superior flavor, lasted longer, and did not require artificial ripening. But, like the Irish Lumper, the global monoculture of the Gros Michel was a fragile tower waiting to topple. The soil-borne fungus Fusarium oxysporum f. sp. cubense initiated the collapse.

The fungus, known as Panama Disease, attacks a banana plant’s root system. It enters the xylem, the plant’s transport system, and effectively blocks the movement of water and nutrients. Leaves collapse, the base of the banana plant splits, and the plant eventually dies. On a commercial scale, the worst part is the fungus can remain in the soil for decades and will not respond to chemical treatment. The only solution is to plant a different crop or a new, disease-resistant banana variety.

The latter is exactly what happened. Our well-known Cavendish was inferior in terms of taste, storage, and consumer preference; the one category it bested was Panama Disease resistance. Now it’s the only banana most of us know. At least for now.

First identified in 1967, a new strain of Panama Disease, known as Tropical Race 4, has been spreading westwards. First rearing its head in Malaysia, Indonesia, and Taiwan in the 1990s, the disease has continued to effect Cavendish bananas in China, Austrailia, Pakistan, and most recently and concerningly, Mozambique.

The banana is the favorite fruit of the US, which on average imports $2.2 billion worth of bananas each year, mostly from the southern hemisphere. Ecuador tops the list of exporting countries, accounting for nearly a quarter of the world’s international supply ($3.2 billon of the fruit) in 2018. Colombia and Panama come in at 6th and 11th respectively.

Industry research of the disease and methods of slowing, preventing, or eradicating it is of utmost importance to growers, producers, and distributors alike. Dr. Ana Notarte points out that the banana industry in her region of the Phillipines (45,000 hectares of bananas) represents 70% of the provincial economy—a reminder of the devastating effects of Ireland’s dependence on the Irish Lumper and the great suffering that followed.

However, not everyone sees Panama Disease as a bad thing (at least ecologically). Many view plant diseases such as Tropical Race 4 as nature’s way of balancing the scale and preventing us from becoming so dependent on industrial monocultures. It is a reminder that the most successful solutions are also the simplest—crop rotations and diverse plantings will succeed and protect where millions of dollars of genetic research often fails. As mentioned previously, agribusiness is changing, and to maintain long-term profitability, the industry must be willing to learn from the past and mimic nature’s principal law of health: diversity.

 

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