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.
Bananageddon strikes again
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.
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.
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.
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.