A little more background about the project

 

Terrifyingly enough, 7% of the world's population could lose its sole source of food as the banana crop is being ravaged by the devastating Panama disease.

Panama disease is caused by the fungus Fusarium oxysporum f. sp. Cubense, which is a soil pathogen that infects the root system of the plant and goes on to colonize the plant through its vascular system. The disease causes the banana to rot and die. Even more problematic is that once soil has been infected, spores of the fungus can continue to infect plants grown nearby for decades, making the infected soil unusable. Currently, the disease cannot be controlled or cured except through soil treatments, such as fumigation, which are often so detrimental to the environment that they are prohibited almost everywhere.

Thanks to this fungus, the banana and the banana industry have had quite a tumultuous history. A century ago, the most grown cultivar was the Gros Michel, a reportedly superior-tasting banana crop that was exploited for its taste and high productivity. This was the only cultivar grown on most banana plantations, making the banana industry reliant on a single Gros Michel monoculture.

Plantation owners soon found themselves in the same trouble that Irish potato farmers did in the mid-1800s. Monocultures do not have any genetic diversity, making them extremely susceptible to pathogens. Without genetic diversity, the species is unable to adapt itself to fight off pathogens.

In the mid-1900s, a pathogen took advantage of this fact. The Fusarium fungus struck, devastating the entire banana industry and driving the Gros Michel to near extinction.

A new solution had to be found quickly and the Cavendish cultivar was soon pushed forward for its similar taste to the Gros Michel, high productivity, and immunity to the fungus. Soon enough, the Cavendish cultivar replaced the Gros Michel and once again became a monoculture.

Presently, history is repeating itself. The Fusarium fungus has evolved into a new strain that is devastating the Cavendish cultivar. Billions of dollars and thousands of hectares of plantation space are lost each year as a result of fungal infection.

Without a solution, the Cavendish cultivar may soon become history as well.

As stated earlier, soil treatments are not a feasible long-term solution because of their toxicity. As a result, a team of research led by Chao Xue and Ryan C. Penton, from Nanjing Agricultural University, Arizona State University, and Hainan University teamed up to create a feasible, long-term solution.

The team decided to focus on biological control, which is the use of living organisms to manage infected soils and improve their quality and has been suggested as an effective method in suppressing Panama disease.

To find this biocontrol element, gene sequencing was done in a soil that suppressed fungal proliferation in order to determine the dominant microbial species within the soil. Through this, Bacillus amyloliquefaciens (BA) strain NJN-6 was found to be the most dominant and had the greatest suppression of fungal activity.

A fertilizer was created by combining this bacterial strain with compost and applied to nursery pots in order to assess the bio-control of this disease. Researchers noticed a 68.5% reduction in disease incidence and a doubled yield when the fertilizer was used.

Though this bacterial strain has demonstrated strong antagonistic activity against fungal growth, it has not been shown to be able to kill the fungus. Our goal is to engineer a new strain of BA that has killing activity.

We found a class of protein, thaumatin-like protein (TLP), that has shown chitinase activity against Fusarium. Chitin is a key component of the fungal cell wall, and by breaking it down using TLP, we hope to kill the fungus. By supplementing the effects of this protein with the existing anti-fungal properties of BA, we hope to create an even more effective and powerful fertilizer.

Time is running out to save the Cavendish banana, but we hope that our method will be an effective, inexpensive, and long-term solution to the pandemic.