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2 Sep 2019

Bananageddon - can we save our beloved bananas?

All around the world banana plantations are under threat from a fungal disease called Panama disease. In recent weeks the first report of the disease in Latin America has hit the headlines, especially in the US which is dependent on crops in this region for their supplies.

This so-called “bananageddon” has the potential to wipe out crops and raise the price of bananas globally. But what is this disease and where did it come from?

panama wilt banana crops fungus
Panama disease, or Fusarium wilt, is the leading cause of "bananageddon."

An economic staple

Bananas are one of the most widely grown plants in the tropics and are consumed pretty much everywhere – even in those countries a long way from tropical regions. In developed countries they are the most widely consumed fruit in the supermarket and in developing countries are a staple food supply for most communities and a major source of disposable income.

Panama disease, or Fusarium wilt, is caused by a specific group of strains of the fungus, Fusarium oxysporum. This fungus has a number of different strains that affect a range of plants – everything from cotton to tomatoes to watermelons – in fact over 150 different host plant species. This makes this fungus one of the top ten plant pathogens that we need to manage in food production around the world.

types of bananas
There are over 1,500 varieties of bananas, all of which could be potentially at risk.
Managing this fungus is a top priority, it has the potential to wipe out crops around the world.
Dr Brett Summerell, Chief Botanist and leading fungi expert

Fungi in our food supply

These wilt disease pathogens infect through the roots and then grow in the water conducting tissue blocking the movement of water from the roots to the rest of the plant. As a consequence the plant will then wilt as though it is under drought conditions. Eventually the infected plant dies.

Once soil is contaminated with this fungus it can survive in the soil for decades and with no effective fungicides the options to control the disease are very limited.

panama wilt banana fungus
Infected plants look similar to those in drought conditions, but lack of water isn't the problem.

Bananageddon strikes again

Race 1 banana fungs
 Fusarium oxysporum f. sp. cubense 

The strains that attack banana are defined as Fusarium oxysporum f. sp. cubense – and there are several different strains or races that attack different varieties of banana. Race 1 was responsible for the demise of the banana variety Gros Michel in the 1950’s and 60’s – starting off unsurprisingly in Panama.

This variety of banana was grown all over the tropics, including Australia, and was the preferred variety for the plantations that existed then. Race 1 effectively wiped out cultivation of Gros Michel bananas but fortunately there was a replacement variety that was resistant to the disease known as Cavendish.

It is this variety – effectively a single clone - that supplies the overwhelmingly vast majority of bananas in supermarkets everywhere and it is now susceptible to a strain of this fungus, called Tropical Race 4 (TR4 which has now been renamed as Fusarium odoratissimum), that is slowly moving all around the world.

F oxy cubens cultures.jpg
Cultures grown in the lab are helping researchers find a solution (Fusarium oxysporum f. sp. cubense).

Biosecurity saves bananas

TR4 was first recorded in south-east Asia, spread to Australia (Northern Territory), other parts of Asia, areas in Africa and now in Colombia. A couple of years ago it was recorded in the Tully region near Cairns but quarantine restrictions have, to date, seen it contained.

F-oxy-cubens-in-situ-2
Panama disease targets bananas' vascular systems to prevent fruit from growing (Fusarium oxysporum f. sp. cubense under the microscope in situ - these tiny spores move easily in vascular system of the plant).

What are the expectations for this disease?

Preventing new outbreaks of the disease is extremely difficult but strict quarantine can achieve this or at least slow down the movement of the fungus. Slowing down the development of new outbreaks are critical as time is desperately needed to develop new resistant varieties to grow in infested areas.

Plant breeding for resistance to diseases like this is very slow – especially in longer lived plants like bananas. New technologies that allow the introduction of genes may help to speed this process up somewhat but are controversial and will need careful evaluation.

banana wilt
Leaves begin to wilt as a symptom of Panama disease and eventually the plant dies.

Curing our crops

This disease highlights the importance of maintaining seed banks and gene banks, especially of our crops and their wild relatives, and in growing as diverse a group of varieties so that new diseases and pests are less likely to take out the whole industry. The challenge now is to develop a number of new banana varieties so that we are not dependent on one banana clone in the future. 

With everyday fruits and vegetables being at risk, the importance of plant science and research has recently become a mainstream topic of conversation. Without plants, we don't have food - and who wants to live in that world?

No plants, no food

Scientists at the PlantClinic are at the forefront of researching, identifying and controlling thousands of plant diseases. Hear how the team identify, research and control thousands of deadly diseases which threaten our food crops and native plants in the Branch Out episode below.

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