Gros Michel bananas
Given that each banana variety is propagated clonally, there is very little genetic diversity in the domesticated plants. This makes bananas especially vulnerable to pests and diseases, as a novel pathogen or pest could quickly decimate a variety if it were to exploit a genetic weakness among the clones. Indeed, this very phenomenon occurred in the late 1950s with the Gros Michel dessert variety, which had dominated the world’s commercial banana business. Richer and sweeter than the modern Cavendish, the Gros Michel fell victim to an invading soil fungus that causes Panama disease, a form of Fusarium wilt. Powerless to breed resistance into the sterile clones and unable to rid the soil of the fungus, farmers were soon forced to abandon the Gros Michel in favour of the hardier Cavendish. Although the Cavendish has thus far been resistant to such a pestilent invasion, its lack of genetic diversity leaves it equally vulnerable to evolving pathogens and pests. Indeed, a strain of Panama disease known as Tropical Race (TR) 4 has been a threat to the Cavendish since the 1990s, and many scientists worry that the Cavendish too will eventually go extinct.
Banana plantation in Guadeloupe
Banana plants thrive naturally on deep, loose, well-drained soils in humid tropical climates, and they are grown successfully under irrigation in such semiarid regions as southern Jamaica. Suckers and divisions of the rhizome are used as planting material; the first crop ripens within 10 to 15 months, and thereafter fruit production is more or less continuous. Frequent pruning is required to remove surplus growth and prevent crowding in a banana plantation. Desirable commercial bunches of bananas consist of nine hands or more and weigh 22–65 kg (49–143 pounds). Three hundred or more such bunches may be produced annually on one acre of land and are harvested before they fully ripen on the plant. For export, the desired degree of maturity attained before harvest depends upon distance from market and type of transportation, and ripening is frequently induced artificially after shipment by exposure to ethylene gas.
Banana plantsBanana plants growing on a plantation. Each herbaceous trunk bears only one bunch of fruit and is cut down after harvest to encourage new growth from the rhizome (underground stem)
The banana plant is a gigantic herb that springs from an underground stem, or rhizome, to form a false trunk 3–6 metres (10–20 feet) high. This trunk is composed of the basal portions of leaf sheaths and is crowned with a rosette of 10 to 20 oblong to elliptic leaves that sometimes attain a length of 3–3.5 metres (10–11.5 feet) and a breadth of 65 cm (26 inches). A large flower spike, carrying numerous yellowish flowers protected by large purple-red bracts, emerges at the top of the false trunk and bends downward to become bunches of 50 to 150 individual fruits, or fingers. The individual fruits, or bananas, are grouped in clusters, or hands, of 10 to 20. After a plant has fruited, it is cut down to the ground, because each trunk produces only one bunch of fruit. The dead trunk is replaced by others in the form of suckers, or shoots, which arise from the rhizome at roughly six-month intervals. The life of a single rhizome thus continues for many years, and the weaker suckers that it sends up through the soil are periodically pruned, while the stronger ones are allowed to grow into fruit-producing plants.
Domesticated bananas growing in a bunch
banana, fruit of the genus Musa, of the family Musaceae, one of the most important fruit crops of the world. The banana is grown in the tropics, and, though it is most widely consumed in those regions, it is valued worldwide for its flavour, nutritional value, and availability throughout the year. Cavendish, or dessert, bananas are most commonly eaten fresh, though they may be fried or mashed and chilled in pies or puddings. They may also be used to flavour muffins, cakes, or breads. Cooking varieties, or plantains, are starchy rather than sweet and are grown extensively as a staple food source in tropical regions; they are cooked when ripe or immature. A ripe fruit contains as much as 22 percent of carbohydrate and is high in dietary fibre, potassium, manganese, and vitamins B6 and C.
