MIGUEL BOYAYANThe news took the whole world by surprise: in ten years, bananas may disappear from the face of the Earth. The prophecy was the raison d’être for the cover story of the January 16 issue of the New Scientist, an important British news magazine, specialized in producing articles on science and technology, which had taken the doleful augury from the mouth of French researcher Emile Frison, a director of the International Network for Improvement of Banana and Plantain. This popular fruit, sterile, incapable of producing seeds and decrepit from the genetic point of view, extremely weakened, was said to be an easy prey for increasingly virulent diseases and pests, which keep on threatening the banana plantations on the planet.
All this is true – except for the fact that not all kinds of banana have their days so numbered. In reply to the apocalyptic tone of the article, the FAO, the organ of the United Nations that monitors agriculture, released a communiqué assuring that there are over 500 varieties of the fruit and that it is not going to disappear any time soon. The entity, though, also recognized that the cultivation of this product faces serious problems due to its low genetic diversity and to the advance of maladies caused by fungi, above all black sigatoca and a new breed of the old panama disease.
“The threat of extinction is limited basically to bananas for export, from the Cavendish subgroup”, ponders Antonio Figueira, from the Center for Nuclear Energy in Agriculture of the University of São Paulo (Cena/USP), in Piracicaba, which is studying the genetic diversity of the fruit in Brazil. Perhaps the apple banana, increasingly rare, may also be running a real risk of disappearing from the map, but this does not imply the end of all the varieties of this tasty yellow skinned fruit.
Although massively present in the European and North American markets – great importers of this tropical food -, the varieties belonging to the Cavendish subgroup, amongst which the Dwarf banana, account for only 13% of the world-wide production of this product. The owner of an annual crop of some 6.5 million tons of bananas, Brazil is the third or fourth largest producer of the fruit (depending on the statistics). “We have to solve a few problems, but the cultivation of bananas in our country, where hybrids of the Prata (Canary) kind can be used, is not threatened”, explains researcher Sebastião de Oliveira e Silva, from Embrapa Cassava&Fruits, in Cruz das Almas, Bahia.
Threat from fungi
Of the two pests that most worry banana producers, only one has reached Brazilian territory, black sigatoca, which entered Brazil in 1998. For the time being, its presence is restricted to the northern region and to Mato Grosso, a secondary areas in terms of banana production. Caused by a fungus called Mycosphaerella fijiensis, which damages the leaves of the plants and leads to an extremely early ripening of the fruit, reducing the useful life of the banana plant, black sigatoca brings about a loss of 50% of the harvest, unless it is combated with chemical products.
The traditional way of holding back the damage done by the disease – more serious than is caused by the kindred yellow sigatoca, another fungal disease that attacks bananas – is spraying the plantation some 40 times a year, a method that is expensive, troublesome, not very environment-friendly, and one that, in time, losses its efficiency. The other pathogen that lays waste the most consumed fruit in the world is breed 4 of the soil fungus Fusarium oxysporum, which causes a more aggressive form of the old panama disease. For decades, less virulent manifestations of the panama disease have been occurring all over Brazil. However, breed 4 of Fusarium has not yet arrived in the Americas, after being identified only in banana plantations in South Africa, Australia and in a large part of Asia.
It is possibly only a question of time for the most aggressive variety of panama disease to land in Brazil and for black sigatoca to spread all over the Brazilian territory. Science, though, is not watching the advance of these diseases with its arms crossed. To hold back these diseases, researchers at home and abroad are resorting increasingly to the genetic improvement of a few varieties of banana. By means of crossbreeding between the edible forms of the fruit and wild kinds of banana, the latter with greater genetic diversity, but improper for consumption, the scientists have now created and launched commercially a few (non-transgenic) varieties that are resistant to these ailments. Pacovan Ken, a prata (canary) banana hybrid created in 2001 by Embrapa Cassava&Fruits, is, for example, tolerant to the two sigatocas and to panama disease. Another cultivar that tolerates these three plagues is the baby prata banana, a variety launched two years ago by the Santa Catarina State Research Company (Epagri).Republish