Wetenschap - 1 april 2019

Breeding new bananas to beat a devastating fungus

tekst:
Albert Sikkema

A fungus called Tropical Race 4, the causal agent of the Panama disease, has infected many banana plantations in the world. So new banana varieties resistant to TR4 are needed. To find this resistance, PhD student Fernando Garcia-Bastidas has tested more than 200 different banana varieties. He now can breed resilient banana plants.

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Banana cultivation is one of the biggest fruit monocultures in the world. It works with genetically identical plants on huge plantations that produce Cavendish bananas only. The banana plants are genetically protected against Panama disease (race 1), but a new fungus has entered the scene: Tropical Race 4. TR4 has already infected banana plantations in almost every country in southeast Asia and it has recently spread to other countries such as Jordan, India and Mozambique. Scientists haven’t found pesticides or biological means to control the disease. If TR4 infected the huge banana plantations in Latin America, the global banana supply would be in danger.

Protected
Fernando Garcia collected 245 different banana varieties from all over the world, grew them in a greenhouse at WUR and infected these varieties with TR4. He found several varieties that didn’t get sick and was able to locate the genes that protected the bananas against TR4, both in Cavendish and wild banana plants. These wild bananas were not producing proper bananas because their fruits were full of seeds, said Garcia. However, they could be used in a conventional breeding programme to introduce resistance to TR4.

Transgenic banana
Garcia collaborated with scientists from Australia during his PhD. They managed to develop a transgenic banana with resistance to TR4. ‘They found a resistance gene in a wild-type banana and transferred this gene to a commercial banana’, explained Garcia. ‘This banana would probably never be on the food market because of GMO regulations, but their research proved that we can breed resistant banana plants.’

5 to 12 years
Garcia is a traditional breeder and has to find other ways to make bananas resistant to TR4. Traditional breeding is far more complex because edible bananas are triploid, which means that they don’t produce seeds and are sterile. Wild-type bananas are diploids; they are fertile, hence they produce seeds and can reproduce sexually. Transforming a gene from a diploid wild banana to a triploid commercial banana through crossing and selecting will take a lot of breeding steps and will take 5 to 12 years, according to Garcia.

Orange or red bananas
He started this breeding process after defending his PhD thesis on 19 March in Wageningen. He now works at the breeding company Keygene on a collaborative project with MusaRadix, a spin-off of WUR. His first aim is to breed a Cavendish with resistance to TR4, and his second aim is to create a bigger variety of edible bananas. For example, Garcia is thinking of developing orange or red bananas resistant to TR4 and other diseases. He hopes to introduce both new and resistant bananas on the European market in some years.


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