As you nibble on a chocolate truffle or bite into a chocolate-dipped strawberry on Valentine’s Day, consider the elongated, ribbed pods of the cacao tree, which made that sweet treat possible. A group of UF/IFAS plant pathologists has partnered with the Mars confectionary company to safeguard those pods – and the precious beans nestled inside – from a devastating disease: black pod rot.
Black pod rot is a disease caused by species in the genus Phytophthora. Meaning “plant destroyer” in Greek, Phytophthora is infamous for including the pathogen that caused the Irish potato famine in the mid-19th century.
Phytophthora-infected cacao pods develop dark lesions, which eventually host white fluffy growth before the pods shrivel into a mummified, inedible state.
Phytophthora megakarya is an especially aggressive species responsible for destroying up to 80% of farmers’ cacao crops, said Mariana Herrera Corzo, a UF/IFAS doctoral student leading part of the project and working under the supervision of Erica Goss, professor, and Jeremy Brawner, courtesy faculty member, both in the plant pathology department.
“Nearly 70% of the global cacao production takes place in Africa, where black pod rot caused by Phytophthora megakarya is rampant,” Herrera Corzo said. “There, we have an epidemic.”
Researchers are conducting preventive breeding to identify cacao plants resistant to Phytophthora species. The process starts in Costa Rica with the evaluation of cacao pods at the Tropical Agricultural Research and Higher Education Center, or CATIE. Mars provides funding for CATIE to ship cacao pods from the center’s germplasm collection to a UF/IFAS lab for inoculation with different Phytophthora species. After a few days, researchers measure the resulting lesions and combine that information with genetic sequencing data from cacao plants and Phytophthora species in prediction models.
The pathologists have examined at least 4,000 pods over the course of more than four years.
“We’re studying the genetics of the plants and the pathogens to develop a prediction model capable of revealing which plant materials are less susceptible to Phytophthora,” Herrera Corzo said.
The team’s research is expected to conclude later this year with the publication of a formal study and the release of their prediction model, which will guide cacao breeders and farmers.
“I feel so committed to this project because I understand the impact that this information could have on small farmers,” Herrera Corzo said. “I’m really proud of what we’re accomplishing.”
