<P> Even though it is no longer viable for large scale cultivation, Gros Michel is not extinct and is still grown in areas where Panama disease is not found . Likewise, Dwarf Cavendish and Grand Nain are in no danger of extinction, but they may leave supermarket shelves if disease makes it impossible to supply the global market . It is unclear if any existing cultivar can replace Cavendish bananas, so various hybridisation and genetic engineering programs are attempting to create a disease - resistant, mass - market banana . One such strain that has emerged is the Taiwanese Cavendish, also known as the Formosana . </P> <P> Export bananas are picked green, and ripen in special rooms upon arrival in the destination country . These rooms are air - tight and filled with ethylene gas to induce ripening . The vivid yellow color consumers normally associate with supermarket bananas is, in fact, caused by the artificial ripening process . Flavor and texture are also affected by ripening temperature . Bananas are refrigerated to between 13.5 and 15 ° C (56.3 and 59.0 ° F) during transport . At lower temperatures, ripening permanently stalls, and the bananas turn gray as cell walls break down . The skin of ripe bananas quickly blackens in the 4 ° C (39 ° F) environment of a domestic refrigerator, although the fruit inside remains unaffected . </P> <P> "Tree - ripened" Cavendish bananas have a greenish - yellow appearance which changes to a brownish - yellow as they ripen further . Although both flavor and texture of tree - ripened bananas is generally regarded as superior to any type of green - picked fruit, this reduces shelf life to only 7--10 days . </P> <P> Bananas can be ordered by the retailer "ungassed" (i.e. not treated with ethylene), and may show up at the supermarket fully green . Guineos verdes (green bananas) that have not been gassed will never fully ripen before becoming rotten . Instead of fresh eating, these bananas can be used for cooking, as seen in Jamaican cuisine . </P>

How many crops does a banana tree produce