Source: New Vision

Publication date: Monday, 9th August, 2010

RESEARCHER: Kiggundu is one of the local scientists involved in research on the banana wilt disease

By John Kasozi

BANANA farmers in East and Central Africa will soon have a reason to smile, as scientists register a major victory in the fight against the deadly Banana Xanthomonas (pronounced ‘zanthomonas’) Wilt(BXW) commonly known as banana wilt disease.

In a major breakthrough, crop scientists last week announced the successful transfer of green pepper genes to bananas, conferring on the popular fruit the means to resist one of the most devastating diseases of bananas in Africa’s Great Lakes region.

“We recently got approval from National Bio-safety Committee of Uganda to carry out confined field trials, which will start in two months. We are now preparing the site for the trials,” said Dr. Leena Tripathi, a plant biotechnologist with the International Institute of Tropical Agriculture (IITA).

How it works

The transformed bananas, infused with plant ferredoxin-like amphipathic protein (Pflp) or hypersensitive response-assisting protein (Hrap) from the green pepper, have shown strong resistance to BXW in the laboratory and screen houses.

The transgenic lines, which are showing promising results, will be evaluated during the confined field trials. The Hrap and Pflp genes work by rapidly killing the cells that come into contact with the disease-spreading bacteria, essentially blocking it from spreading any further.

The mechanism known as Hypersensitivity Response also activates the defence of adjacent and even distant uninfected plants, leading to a systematic acquired resistance.

“The genes from green pepper were acquired from Academia Sinica, in Taiwan. These genes have been tested on other crops like flowers (Calla lily), rice and vegetables as a proof of concept for disease resistance. These genes were tested for the first time in banana in Uganda,” explained IITA country head Tripathi.

“The research has taken us five years to reach this stage of developing transgenic banana. We have transformed four cultivars, Sukali Ndizzi, Kayinja, Mpologoma and Nakinyika. This is a joint project between IITA, National Agricultural Research Organisation (NARO) and African Agricultural Technology Foundation (AATF),” she added.

Promising results

Tripathi explained that although it is still a long way before the transgenic bananas find their way into farmers’ fields, this breakthrough is a significant step in the fight against the deadly banana wilt disease.

 

“There are presently no commercial chemicals, bio-control agents or resistant varieties to help control the spread of BXW.

“Even if a source of resistance is identified, developing a truly resistant banana would be extremely difficult given the sterile nature and long gestation period of the crop,” she said.

History of Banana Wilt

BXW was first reported in Ethiopia 40 years ago on Ensete, a crop relative of banana, before it moved on to bananas.

Outside of Ethiopia, it was first reported in Uganda in 2001, then rapidly spread to the Democratic Republic of Congo, Rwanda, Kenya, Tanzania, and Burundi, leaving behind a trail of destruction in Africa’s largest banana producing and consuming region.

The destructive bacterial disease affects all banana varieties including the East African Highland bananas and exotic dessert, roasting, and beer bananas, causing annual losses of more than $500m across East and Central Africa.

Dr. Andrew Kiggundu, the head of banana biotechnology research National Agricultural Research Laboratories Institute in Kawanda, says: “The economic impact of Banana Xanthomonas Wilt (BXW) is potentially disastrous, because it reduces banana yields. The farmers do not have the option of relocating to new planting sites that are infection free.

“If uncontrolled, BXW would cause an estimated production loss of about 53% over a 10-year period. Overall economic losses were estimated at $2 billion to $8 billion over a decade, arising from price increases and significant reductions in production.”

The disease causes yellowing and wilting of the leaves, uneven and premature ripening of the fruit, withering and rotting of the whole plant causing complete yield loss.

However, it can be controlled by removal of the male flowers, de-budding and sterilising farm implements used.

However, adoption of these practices has been inconsistent, as farmers find them rather tedious.

Contact Dr. Leena Tripathi

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article thumbnailFarmers in the East African Highlands, centred on Uganda, depend on bananas as a staple food crop and a source of income. The harvest, however, is threatened by many pests and diseases that also...
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The vast majority of the bananas currently grown and consumed were not conventionally bred but are selections made over probably thousands of years from naturally occurring hybrids. Cultivated bananas are very nearly sterile and as a consequence are not propagated from seed but rather through vegetative propagation, primarily suckers as well as more recently micropropagated or tissue cultured bananas. These factors, very old selections, near sterility and vegetative propagation, mean that these bananas have not been genetically improved either for resistance or improved quality and are becoming increasing in affected by serious pests and diseases.

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