Research: Bananas with resistence to Fusarium TR4

A team at the University of Queensland is taking the next step in their search for a banana that has resistance against Panama disease. Led by Professor James Dale, they have already produced a genetically modified Cavendish that can stand up to tropical race 4 - the worst form of the soil-borne fungal disease[1].

Called Fusarium wilt or Panama disease, it is a devastating disease of bananas. In the first half of last century, it caused one of the most serious plant disease epidemics in history. During that period, Fusarium oxysporum cubense, the fungus responsible for Fusarium wilt, caused a major epidemic in commercial banana plantations in South and Central America in the then dominant export cultivar Gros Michel. This epidemic was caused by Fusarium TR1 and led to the almost complete replacement of Gros Michel with Cavendish, which is resistant to Fusarium TR1. Cavendish now accounts for more than 40% of world's banana production. Despite this, Fusarium TR1 continues to cause significant disease in a wide range of other locally produced and traded banana cultivars.

Fusarium invades through the roots and then causes extensive necrosis leading to plant death. The fungus is disseminated in infested soil, infected planting material and water including irrigation water and floods, and can remain in the soil for more than 40 years. In the early 1990s,a novel form of Fusarium was recognized in South East Asia, which differed from Fusarium TR1 in that it infects and kills Cavendish as well as a number of other important TR1-resistant cultivars. Fusarium TR4 now devastates Cavendish plantations around the world and continues to spread. Of the banana-producing continents, only the Americas have yet to record TR4.

There is no effective chemical control for Fusarium TR4. Although somaclonal variants of Giant Cavendish (Giant Cavendish Tissue Culture Variants (GCTCVs)) with varying levels of tolerance to TR4 have been generated in Taiwan through tissue culturing6, these are considered a short-term solution to disease control at best due to lack of immunity and undesirable agronomic traits7. The lack of effective TR4 control measures and the devastating impact of the disease make the deployment of resistance genes an obvious and attractive strategy.

Now scientists from the University of Queensland report the generation and field-trialling of transgenic Cavendish banana plants and the identification of lines with robust resistance to TR4.

Professor Dale said the field trials showed high expression of a gene derived from a wild banana provided resistance to TR4 disease. "Although (this gene) is also present in Cavendish it is not expressed." Gene snipping might fix that.

[1[ Dale et al: Transgenic Cavendish bananas with resistance to Fusarium wilt tropical race 4 in Nature Communications – 2021. See here.