The researchers believe their discovery represents a significant advance in basic ecology. It also offers the potential for enlisting such fungal armies to protect cacao trees from the pathogens that damage the trees, which are the source of the world's chocolate. Successful cultivation of cacao trees in American rainforests, they said, offers a viable economic alternative to clearing the forests for ranching. Field tests of fungi as biological control agents are already underway, said the researchers.
The biologists published their findings in the Dec. 23, 2003, issue of the Proceedings of the National Academy of Sciences. Lead author on the paper was A. Elizabeth Arnold, a postdoctoral fellow in the Duke University Department of Biology. Other co-authors are Luis Meja, Damond Kyllo, Enith Rojas, Zuleyka Maynard, Nancy Robbins and Allen Herre of the Smithsonian Tropical Research Institute in Panama. Their research was sponsored by the Research Institute and by grants from the American Cocoa Research Institute, the World Cocoa Foundation, the M&M/Mars Division of Masterfoods, the Andrew Mellon Foundation and the National Science Foundation.
In their study, the scientists concentrated on "endophytes," which are fungi that infect healthy plant tissues without causing disease. Endophytes of woody plants land as airborne spores, burrowing into the plant tissues and living in the spaces between cells -- a process called "horizontal" transmission. According to Arnold, studies on grasses had revealed that fungi passed down from generation to generation -- called vertical transmission -- offered those plants benefits such as resistance to pathogens, drought and herbivores.