Genes from green pepper rescue Africa's banana from deadly wilt disease

In a major breakthrough, scientists have successfully transferred genes from green pepper to bananas that enable the crop to resist the deadly Banana Xanthomonas Wilt (BXW), the most devastating disease of banana in the Great Lakes region of Africa. The researchers are now ready to start confined field trials in Uganda.

The destructive bacterial disease affects all varieties including the East African Highland bananas and exotic dessert, roasting, and beer bananas causing annual losses of more than US$500 million across East and Central Africa. The crops are also under threat from another deadly disease, the banana bunchy top disease.

The transformed banana, infused with proteins from the green pepper, have shown strong resistance to BXW in the laboratory and screen houses. Some of the findings have been published in the current issue of Molecular Plant Pathology journal.

Dr Leena Tripathi, a biotechnologist with International Institute of Tropical Agriculture (IITA) and the lead author of the paper, says that although there is still a long way to go before the transgenic bananas find their way into farmer’s fields, this breakthrough is a significant step in the fight against the deadly banana disease.

“The transferred genes work by rapidly killing the cells that come into contact with the disease-spreading bacteria, essentially blocking it from spreading any further. Hopefully, this will boost the arsenal available to fight BXW and save millions of livelihoods in the Great Lakes region,” she said. “Furthermore, the mechanism- known as Hypersensitivity Response - also activates the defense of adjacent and even distant uninfected plants leading to a systematic acquired resistance."

Dr Tripathi adds that there are presently no commercial chemicals, biocontrol agents or resistant varieties to help control the spread of BXW. She emphasizes that 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.

The researchers from IITA in partnership with the National Agricultural Research Organization (NARO) and the African Agricultural Technology Foundation (AATF) are now ready to evaluate these promising resistant lines under confined field trials after the National Biosafety Committee of Uganda recently approved the conduct of the tests.

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

The disease can be controlled by removal of the male flowers, debudding, and sterilizing farm implements used. However, the adoption of these practices has been inconsistent at best as farmers feel debudding affects the quality of banana and sterilizing farm tools is tedious.

Scientists believe that the novel plant proteins can also provide effective control against other banana diseases in other parts of the world such as “Moko”, Blood and “Bugtok” that are also caused by bacteria similar to the BXW pathogen. These genes were acquired from Academia Sinica, Taiwan.

 

August 2010