This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from the USDA's rich science and research portfolio.
What a long, strange trip it’s been for newly discovered South American varieties of cacao beans—all the way from the remote Amazon Basin in Peru to Agricultural Research Service (ARS) labs in Beltsville, Md., where the beans are being studied as a possible source of future high-end chocolates that could one day be marketed, like fine wines, by geographical provenance.
In the course of cacao germplasm collection trips in Peru in 2008 and 2009, scientists found groves of wild cacao trees that might yield treasures of two sorts: a source of new, unique chocolate flavors that are distinctly Peruvian, and beneficial fungi that could form the basis of new biological control weapons against fungal diseases like witches’ broom that now ravage the cacao crop.
The ARS scientists and their Peruvian collaborators packed up hundreds of live samples gathered from 12 watersheds and brought them home for an in-depth look at the specimens’ DNA. One of the finds, discovered by collaborators from the company Marañón Chocolate, was Pure Nacional, an old, very rare and highly coveted variety of cacao. The scientists also have identified three completely new populations of cacao that were not previously known to science.
Like many tropical tree crops, cacao beans lose their viability quickly after being harvested, so varieties of cacao must be maintained in living germplasm banks. While there are more than 5,000 different varieties of cacao in germplasm collections around the world, the ARS scientists say those represent only a small fraction of the cacao genetic diversity that still exists in the wild.
During the 2008 trip, the scientists noted relatively low levels of witches’ broom in wild cacao trees in the upper Amazon region. This suggests that there’s a high level of witches’ broom resistance in the wild Peruvian cacao populations. The scientists isolated fungi from disease-free leaves and trunks of the wild trees, and say these fungi, now being evaluated at ARS labs, could be the starting point for new biological controls against witches’ broom. That’s sweet news for chocolate makers—and chocolate aficionados, too.
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As USDA’s s chief scientific research agency, ARS is leading America towards a better future through agricultural research and information. ARS conducts research to develop and transfer solutions to help answer agricultural questions that impact Americans every day. ARS work helps to:
- ensure high-quality, safe food, and other agricultural products;
- assess the nutritional needs of Americans;
- sustain a competitive agricultural economy;
- enhance the natural resource base and the environment; and
- provide economic opportunities for rural citizens, communities, and society as a whole.
