Scientists seek cure for devastating witches' broom disease of the chocolate tree
In the early 1900s, Brazil was the world's largest producer of cocoa. Chocolate trees (Theobroma cacao) were cultivated in a 800, 000 ha region of rainforest in the state of Bahia, beneath a dense canopy of native shade trees. Whereas the surrounding rainforest was a biodiversity hotspot, the chocolate trees, which were derived mainly from a handful of seeds introduced in the mid 1700s, had very low levels of genetic variation. According to Brazilian scientist Gonçalo Pereira, "This scenario created a very romantic, but extremely fragile situation". Genetic variation is important for a population's survival, as genetically variable populations are more resistant to pathogens. In 1989, disaster struck in the form of a devastating fungus named Moniliophthora perniciosa. In a ten-year period, the fungus eradicated around 70 percent of Brazil's chocolate trees, resulting in an economic and social catastrophe that affected two million people.