GM bid to fight banana disease

Ban on GM crops waived for scientists’ tests after bacterial disease causes annual crop losses of $500m

March 09, 2011 05:13 pm | Updated 05:13 pm IST

In this file photo a banana seller display flags with the portrait of Ugandan President Yoweri Museveni's at a rally to celebrate the Presidential victory at Kololo Airstrip, Uganda.

In this file photo a banana seller display flags with the portrait of Ugandan President Yoweri Museveni's at a rally to celebrate the Presidential victory at Kololo Airstrip, Uganda.

Most countries would resent being called a banana republic. Uganda prides itself on it. A typical adult here eats at least three times his or her body weight in bananas each year, more than anywhere else on Earth. Different varieties are steamed, boiled, roasted, turned into gin and beer, or simply peeled and eaten raw, such as the tiny sukali ndizi, considered by some experts to be finest banana in the world.

“Breakfast, lunch and dinner, 365 days a year,” said Arthur Kamenya, whose taste for the fruit is so strong he quit his job as a graphic designer to grow it commercially. “And people still crave more.” But it is a craving under threat. In recent years a devastating bacterial disease has swept across Uganda and, to a lesser extent, neighbouring countries, causing annual banana crop losses to the region of more than $500m. The rapid spread of banana Xanthomonas wilt, or BXW, which destroys the entire plant and contaminates the soil, “has endangered the livelihoods of millions of farmers who rely on banana for staple food and income”, according to an article in the journal Molecular Plant Biology last year.

With no resistant varieties or chemical cures available, growers such as Kamenya have been forced to destroy large sections of their plantations. For smaller farmers the damage has been so severe many have given up on the fruit.

But local scientists have not. On a sprawling campus outside Kampala, Wilberforce Tushemereirwe and his colleagues at the National Banana Research Programme have been on a quest to defeat the disease by building a better banana. This has involved adding to the fruit a sweet pepper gene that has already improved disease resistance in several vegetables.

Laboratory tests on the genetically modified bananas have been highly promising, with six out of eight strains proving 100% resistant to BXW. Field tests have now started in a fenced-off, guarded plot on the edge of the campus.

Results from the trials, expected later this year, could have a strong bearing on the country’s future food security - and indeed its entire policy on agriculture. GM crops are still banned in Uganda, and the scientists had to get special permission just to conduct their tests. While acknowledging that it is a highly controversial topic, Tushemereirwe says the risk of doing nothing is too great.

“If we just leave this, bananas will slowly disappear from Uganda,” he said.

BXW was first reported in Ethiopia in the 1960s, but was only identified further south in 2001, initially in Uganda, and then Rwanda, the Democratic Republic of Congo, Kenya, Burundi and Tanzania. Uganda was particularly vulnerable because of the scale of its banana production, second only to India which has a population 35 times larger.

With a single plant lasting for many years and providing a large bunch of fruit every few months, bananas are a key crop for small farmers. They are also a crucial source of sustenance, estimated to account for more than 30 per cent of Ugandans’ daily calorie intake. According to Tushemereirwe, the average adult eats 200-250kg of bananas a year - and twice that in some areas.

Most of that is matooke, a long green banana, which is usually steamed and mashed and eaten with beans, peanut sauce or meat. That’s what Kamenya planted six years ago on his farm in Galamba, about an hour’s drive from the Ugandan capital. But soon he realised some of the plants were sick, with yellowing leaves and the fruit ripening prematurely.

Kamenya, a powerfully built 37-year-old, was forced to dig up 1,500 of his 4,500 plants, destroy them, and allow the soil to lie fallow for at least six months. He also had to carefully sterilise his farm tools. This eventually helped control the disease, though he still has problems. “Look how this plant has rotted,” he said, slicing through the trunk of a banana plant with a knife to reveal yellow ooze.

Few areas of Uganda have escaped the disease, which is transported by insects such as bees and wasps. But traditional farming practices also ensured its rapid spread. Infected young shoots of banana plants are shared with neighbours, while the use of banana leaves to cover bunches of fruit headed to market quickly transferred the disease to new areas.

In central Uganda, one of the main banana-growing regions, BXW hit up to 80% of farms, sometimes wiping out entire fields. Small-scale farmers, who could not afford to let their gardens lie empty for months before replanting, switched to other crops.

Tushemereirwe, with the International Institute for Tropical Agriculture and African Agricultural Technology Foundation (IITA), decided a GM solution was the best way forward. Academia Sinica, the Taiwanese research institute that pioneered the sweet pepper gene technology, agreed to issue them with a royalty-free licence. The sweet pepper gene produces a protein that kills cells infected by disease-spreading bacteria.

Leena Tripathi, a plant biotechnologist at IITA who helped steer the project, said introducing the gene did not affect the quality of the banana and presented no health risks. “The beauty of the genetic engineering is that you can be very precise,” she said.

Other GM banana experiments are under way in Uganda, including one to fortify the fruit with iron and vitamin A. But concern about GM foods in Uganda means they could face a long battle before any of the transgenic bananas find their way on to the market.

A study by Enoch Kikulwe, a Ugandan assistant professor of international food economics at the University of Gottingen, Germany, revealed more opposition to GM crops among the elite than those in poorer villages. Most studies show that better education led to more acceptance of GM foods, he said.

But for Kamenya the farmer, the anti-GM stance was hypocritical. “Most of the people against this have choices,” he said. “Somebody who is hungry does not have a choice. GM, organic or whatever - you have to feed the people.” Copyright: Guardian News & Media 2011

How to eat them

The super-sweet dessert bananas are the easy option. The home-brewed banana gin is a choice for only the highly adventurous. For authenticity, however, matooke, the national staple that looks like buttery mashed potato on the plate, is the only way to go.

Also known as east African highland bananas, the green matooke fruits are for cooking only - ideally steamed on an open fire. To start, water is poured into a large pot and covered with banana stalks. The peeled bananas are wrapped in the plant leaves, with the bundle lowered into the pot, resting on the stalks, above the water.

The fruit is then steamed for a few hours, going from hard to soft, white to yellow. Still wrapped in the leaves, the bananas are then mashed.

The dish can then be served on a new leaf, together with beans, other vegetables or peanut sauce.

It is an acquired taste, and to the uninitiated it can seem heavy and bland. But once you’ve got it, Ugandans say, there’s no going back to rice and potatoes.

Copyright: Guardian News & Media 2011

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