UNIVERSITY PARK, Pa. — Chocolate-producing cacao trees that are resistant to a major pathogen were identified by an international team of plant geneticists. The findings point the way for plant breeders to develop trees that are tolerant of the disease.
The method researchers used to rapidly identify resistance genes could be used for any trait that has a genetic link in any plant, according to the team’s leader, Mark Guiltinan, professor of plant molecular biology, Penn State College of Agricultural Sciences. He contends that the strategy represents a major step forward in the quest to develop disease resistance in long generational plants such as trees.
The focus of the study was the tropical tree Theobroma cacao, the source of chocolate. Its seeds are a major export from many producing countries in Central and South America, Africa, and Asia — but every year, 30-40% of preharvest yield is lost to diseases.
For a long time, scientists have been trying to devise ways to reduce those losses, Guiltinan pointed out, adding that bolstering cacao’s resistance to disease is the most efficient and environmentally friendly approach for disease management.
To determine how best to boost cacao resistance, Guiltinan assembled what he called “an amazing transdisciplinary team.”
The researchers set out to measure the susceptibility of 60 genetically diverse genotypes of cacao to Phytophthora palmivora — a major cacao pathogen with global importance — by first collecting leaf samples from cacao trees at the International Cocoa Collection (CATIE), in Turrialba, Costa Rica.