Vanilla's genetic flavor is bland: low diversity suggests difficulty in fighting off pests

Science News, July 19, 2008 by Rachel Ehrenberg

Scientists have now tasted the genetic makeup of Vanilla, the orchid whose pods bestow flavor on ice cream, perfume and rum. And they found it's pretty plain.

Genetic diversity in Vanilla planifolia is "very, very, verylow," says Pascale Besse, a plant geneticist at the joint research center PVBMT Cirad and the University of Reunion who led the research, which appears in the July American Journal of Botany. Besse and colleagues examined a stretch of genetic code in more than 300 vanilla plants from Reunion Island, Madagascar, French Polynesia, Mexico, Central America and Brazil.

The findings are worrisome, the researchers say. The blandness of the plant's DNA suggests that cultivated vanilla is a monoculture, lacking the genetic variation that would help in a face-off with pests or disease.

But even with Plain Jane DNA, there is consistent physical variation among the surveyed orchids--differences in leaf shape and size, pod shape, stem thickness and self-fertility, the researchers report. This physical variation in vanilla plants, without the variation at the genetic level, suggests some intriguing things might be going on--perhaps epigenetic modifications that don't actually alter the DNA code but can crank up the volume of certain genes while silencing others.

"This opens the doors to a lot of research," comments Ken Cameron, a botanist at the University of Wisconsin-Madison. "By many estimates, vanilla flavor and fragrance is the most popular on Earth--it's in thousands of products." Cameron says other work has shown interesting chromosomal traits in vanilla, and the new study offers hope that the crop will survive into the future despite its lack of genetic diversity.

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Tapping into the biochemical diversity, investigating hybrids and looking more closely at some of the other 50 to 90 related species could provide a lot of variation for breeders to work with.