Every year, 20-30 percent of the precious cocoa pods that make our delicious chocolate are woefully killed by disease. But don’t panic! Science has come to the rescue, as researchers from the Pennsylvania State University have found a way to genetically modify cacao trees to make them more resistant to disease. Yay!
Before making its way into a Hershey’s wrapper, chocolate starts its life in tropical countries like Ghana and Brazil. Cacao plants are farmed, and the cocoa pods they produce are harvested before the beans inside them are used to make chocolate. It’s a multi-billion-dollar industry and many people rely on our hunger for chocolate as a means of survival. But every year, more than a fifth of cocoa pods are destroyed by disease before the harvest even begins.
"In West Africa, severe outbreaks of fungal diseases can destroy all cacao fruit on a single farm," said Andrew Fister, lead author of the new study published in Frontiers in Plant Science. "Because diseases are a persistent problem for cacao, improving disease resistance has been a priority for researchers. But development of disease-resistant varieties has been slowed by the need for sources of genetic resistance and the long generation time of cacao trees."
To tackle the problem, Fister’s team turned to CRISPR-cas9 – a revolutionary gene-editing technique that literally allows scientists to cut and paste sections of DNA to create a desired effect. It’s already shown huge promise in both medicine and food production, and is already being tested on cacao trees in an attempt to save them from climate change.
The researchers used CRISPR-cas9 to change the DNA of the Theobroma cacao tree, which is native to tropical areas of Central and South America. The cocoa beans it produces are used to create all sorts of chocolatey goodness, from cocoa powder and ganache to good old fashioned Dairy Milk.
Previous research had spotted a gene – known as TcNPR3 – that suppresses the cocoa plant’s ability to fight disease. Therefore, the researchers used CRISPR-cas9 to "delete" this gene in detached cacao leaves. When they analyzed the leaf tissue afterward, they found deletions in 27 percent of TcNPR3 copies. They then infected the leaves with a disease that affects cacao plants called Phytophthora tropicalis and discovered their experiment had been a success, as the plant’s ability to fight off the disease had significantly improved.
To test how the technique affects an entire plant, the team have also modified cacao embryos, but we’ll need to wait for them to grow into adult trees to find out the result.
The team hope to identify more genes related to disease resistance in cocoa plants. Their end goal is to improve the lives of smallholder cocoa growers and stabilize the supply of our beloved cocoa, which, as well as being threatened by disease, is under pressure from a booming global demand and the perils of climate change.