The Panama disease, a fungal infection ravishing the Cavendish banana, the type that accounts for 95% of the bananas sold around the world, is spread through the soil. The scourge has become so rampant that as well as destroying the businesses of banana farmers around the world it threatens the future viability of our favourite banana variety. The answer devised by biotech scientists at the Netherlands’ Wageningen University, the world’s leading agritech research facility, is bananas grown without soil.
The fungus that causes the Panama disease is spread by soil movement, which is usually the result of workers and machinery going about their everyday tasks on banana plantations. But it has proven rife and has devastated crops across South-East Asia, Australia, Mozambique and the Middle East. The Cavendish banana is particularly vulnerable to epidemics such as the current Panama disease outbreak because it is a monoculture based on a single genetic clone. So every banana plant is equally susceptible to infection.
This was also the case for the Gros Michel banana which was, before the Cavendish, the most commonly eaten variety. The type was wiped out by the first strain of the Panama disease fungus, which is thought to have originated in Taiwan in the early 1960s. The impact was such that the risk of infection meant it became economically unviable to continue to farm the Gros Michel. The new variety of Cavendish which replaced it was not as vulnerable to the fungus. However, the fungus has now adapted to the Cavendish. It hasn’t yet reached Latin America, where 75% of banana exports originate, and biotech scientists have been working frantically to combat the spread of Panama so it doesn’t. The transfer of infected soil, plants and materials to areas the fungus is not yet present is key.
At Wageningen University, the approach has been to find a way to grow banana plants without soil. That’s been achieved by replacing it with ‘rockwool’ which is composed of chalk and Basalt rock, with minerals added to the mix to provide the sustenance that would normally come from the soil. However, that’s not a technique that can be employed across huge banana plantations. It can however, be used as a buffer, separating sections of plantations like a fire corridor in forests, and help prevent any outbreak of Panama quickly spreading across a whole region.
Longer term, biotechnologists are working on banana breeding programmes that hope to combine the Cavendish with wild varieties resistant to the Panama disease. UK bio/agritech start-up Tropic Biosciences is also hopes to use gene editing to build resistance into the Cavendish without slightly changing its taste and texture by mixing other breeds in.
But biotech/agritech advances should mean the Cavendish avoids the same fate as it fungus-consumed forebear the Gros Michel.