Panama Disease - History

History

Gros Michel or 'Big Mike' was an early export cultivar of banana. This cultivar was wiped out by Panama disease in the 1950s. The disease first appeared in Suriname, then made its way to the Caribbean, and, by the 1920s, to Honduras, the world's largest producer of bananas at the time. Although there are many banana cultivars, Gros Michel was especially suitable for export to non-tropical nations. A search for a substitute located the Vietnamese Cavendish cultivar, which is resistant to the disease. However, more care is required for shipping the Cavendish banana, and its quality compared to Gros Michel is debated.

Recently, a new strain called 'tropical race four Panama disease' has begun to attack Cavendish banana plants in south Asia. Given the high volume of modern international trade, banana producers expect this strain to spread through Africa and into South America and the Caribbean.

Plant breeders and geneticists are trying to develop new cultivars that are resistant to this new strain of Panama disease. Unfortunately, such efforts are progressing slowly because the triploid banana cultivars selected for human consumption are seedless and reproduce asexually, which decreases genetic variation and makes breeding difficult.

The Big Mike was the only banana that Americans ate, bought, or thought of from the late 19th century until after World War II. The Gros Michel eventually disappeared. A disease began to devastate banana crops not long after the first banana trees were planted in Central America. The problem was discovered in Panama and named after the country. Panama disease, which is actually a fungus (Fusarium oxysporum), is particularly virulent. It is transmitted through soil and water. F. Oxysporum can live dormant in the soil for about thirty years or until it is stimulated to germinate by a susceptible host. It usually enters through the root system and travels into the xylem vessels. As the fungus disrupts the plants vascular system, the leaves turn yellow and begin to wilt. After it finishes its cycle the plant eventually dies from dehydration. Once it strikes a plantation, it quickly destroys, and then moves on. The reason the fungus is so devastating is not just because it is so strong. It is also because the banana plant has a disadvantage.

Modern breeds of banana are not able reproduce on their own. They have no seeds and the male flowers do not produce viable pollen. New bananas develop through asexual reproduction. One banana plant creates another in a process similar to taking a cutting from a rosebush. Due to this method of reproduction, bananas are nearly identical genetically; Therefore they have a uniform susceptibility to the same diseases. Once a disease, fungus, or pest figures out a way through the plants defenses it can quickly overcome the entire cultivated area.

That is exactly what happened to the Gros Michel. The fungus spread from the country it was first discovered to neighboring countries, moving north through Costa Rica all the way to Guatemala and South into Colombia and Ecuador. The process took decades.

By 1960, fifty years after the malady was discovered, the Gros Michel was in effect wiped out. The banana industry was in a serious crisis. It was only at the last minute that a new banana was adopted. The Cavendish was immune to Panama disease, and in a few years the devastated plantations resumed business as usual, and the transition went smoothly in the American market. However, the Cavendish was introduced into a different, faster moving world. At first, it was grown in exactly the same places as its predecessor. Yet, by the end of the 1970s, populations across the globe began moving into cities. If they wanted to eat bananas, they needed one that could be transported great distances intact, ready to ripen, and with a consistent enough taste for consumers. Malaysia was a place that needed such a banana. Cavendish banana plantations were new to the country in the 1980s, but they rapidly became big business. Thousands of acres of rain forests and former palm oil plantations were being shifted to banana production. Within a few years, the newly planted fruit began to die. An unknown pathogen was working its way into the roots of the plant, discoloring leaves, and choking off the plants water supply.

It took several years for scientist to identify the problem. They discovered it was Panama disease, striking the banana variety that was supposed to be invulnerable. It turns out that the Cavendish had not actually been immune to the affliction, only the particular strain of the fungus that destroyed the Gros Michel. The version of the fungus that annihilated the Gros Michel was only found in the Western Hemisphere, but the version that was found in Malaysian soil was different. It was deadly to the Cavendish variety, it killed and moved faster, and it inspired more panic than its earlier counterpart. The newly discovered strand of F. oxysporum was named Tropical Race 4. Today, the blight is tearing through banana crops worldwide. It has spread to Pakistan, the Philippines, and Indonesia. It is on the rise in Africa and Australia. While it is yet to arrive in Latin America, scientists believe that it will. In a race against time, scientist have been trying to modify the fruit to make it resistant to Panama disease as well as many other serious banana afflictions, ranging from fungal, bacterial, and viral infections to burrowing worms and beetles. Researchers are combing remote jungles searching for new, wild bananas. They are crossbreeding one banana with another hoping to generate a new variety with a strong resistance to illness. Genetic engineers are even adding genetic material from altogether different fruits, vegetables, and fish. Some believe the best hope for a more resilient banana is through genetic engineering. However, the resulting fruit needs to taste good, ripen in the correct amount of time, travel long distances undamaged, and be easy to grow in great quantities. Right now, no such banana exists that meets all of these requirements.