Saving the Banana
Dec 10, 2018
According to a 2014 examination of global production and consumption patterns, the banana is the most widely consumed fruit in the world (if you don’t view tomatoes as fruits), with estimated consumption in that year of more than 114 million tons. In most countries, it is eaten in raw form as a side dish or in desserts, but in parts of Africa it is viewed as a staple commodity and is typically cooked as a starch dish. While global per capita consumption of bananas was estimated at about 26 pounds per year in 2013, in East Africa it is estimated to be about 450 pounds per year.
The fruit is highly nutritious--eating a single banana provides an individual with an estimated 20 percent of the recommended daily requirements for vitamin B6, 17 percent of vitamin C, and 12 percent of both potassium and dietary fiber.
However, global banana production is now under serious assault on two fronts. In the 1960’s, plant breeders developed the Cavendish variety of banana, which become the dominant variety grown for the export market worldwide. The Cavendish prevailed not because it was better tasting than other varieties, but because it was resistant to a fungal infestation known as Panama disease which had wiped out the previous dominant variety known as Gros Michel. The Cavendish variety is now under threat of extinction because of the emergence of a new strain of fungal disease which it has no resistance to. The situation is made worse because the Cavendish plants being grown are nearly all clones of the original cultivar, so there is almost no genetic diversity within the banana export supply to soften the blow.
First identified in the 1970’s in Taiwan, this new strain known as ‘Tropical Race 4’ or TR4, has now spread across Asia, Australia, the Middle East, and reached Mozambique in southeastern Africa in 2013. Although most of the bananas grown in Africa are not Cavendish cultivars, they are also vulnerable to TP4, and account for about half of the staple crop production in central and east Africa.
Banana production in Africa is under threat from additional diseases as well. In Uganda and the Democratic Republic of the Congo, farmers are facing Banana Xanthomonas wilt, a bacterial infection that causes bananas to rot by blocking their vascular systems. This infection is carried by insects, and spreads faster than fungal diseases. Other diseases endemic to Africa are spreading in the banana population as well, including bunchy top virus and black sigatoka, a fungal disease that attacks the leaves on banana plants.
Research is underway to develop varieties of bananas that are resistant to these various diseases. A banana variety resistant to TR4 has been found in Mozambique, but it is full of seeds and not very tasty. There is an effort to cross-breed this variety with the Cavendish cultivar to generate some resistance to the disease in a commercially viable fruit. Plant breeders in Taiwan have already developed Cavendish cultivars with some resistance to TR4 as well.
There is also research using the tools of biotechnology to introduce genes from other species to create banana resistance to TR4. Scientists at Queensland University in Australia have been working for nearly a decade to develop such bananas, using genes from wild bananas that have exhibited resistance to TR-4 and a separate transgenic project that is using genes from a nematode with similar properties. Scientists at the International Center for Tropical Agriculture (CIAT) are working to develop banana cultivars that are resistant to bacterial wilt and nematodes, looking at incorporating genes from pepper plants with those traits.
Funded by the Bill and Melinda Gates Foundation, scientists in Uganda have been working on a separate line of GMO bananas which have enhanced vitamin A content. For the last few years, the government of Uganda has been trying to pass legislation that would allow field trials and ultimately cultivation of GMO bananas in their country. Despite strong opposition by anti-GMO activists, the parliament passed such a law in late November 2018 and is awaiting the approval of President Musevani. The Ugandan scientists believe their GMO banana could be released for commercial planting by 2021 once the new biosafety law is in place.