People who love the taste of mustard and horseradish on their favorite food have brassica and caterpillars to thank for their delectable flavor, according to new research.

In a paper published in the journal Proceedings of the National Academy of Sciences, researchers from the University of Missouri's Bond Life Sciences Center and other academic institutions studied how these well-known condiments received their distinct taste.

They discovered that the mustard oils that produce the flavor are actually a by-product of the brassica's defense mechanism, developed over the course of millions of years, against pests. Intelligent insects such as cabbage butterflies, however, devised ways to bypass this defense. This led to a virtual arms race between the insects and the plants.

Chris Pires, an associate professor of biological sciences and co-author of the study, said that they found genetic evidence that prove the ongoing struggle between known pests, like the cabbage butterflies, and plants, such as cabbages, broccolis and mustards.

He explained how these plants were able to duplicate their genome and how the resulting copies of their genes eventually developed new traits, such as glucosinolates, to defend themselves. The cabbage butterflies then responded by creating new methods to fight against these defenses.

The researchers noted that while the glucosinolates that the mustard plants developed may be appealing to human taste, they are highly toxic to small caterpillars. These chemicals are also the ones that give radishes, capers and cauliflower their highly particular yet complex flavor.

Pires said that the spices and flavors of plants serve particular functions as part of their evolution.

Scientists have long theorized that the distinct flavor of some plants is somehow associated with the development of the insects that eat them, but the latest study is the first of its kind to map out how this particular trait evolved.

The researchers started by lining up the family trees of Brassicales and early cabbage butterflies according to their evolution. They discovered that each time the plants develop a new type of glucosinolate, their family tree would then branch out into various new species with more complex flavors.

Pires said this chemical is what keeps bugs away from the plants as it turns their guts inside out.

The researchers believe the findings of their study can help develop advanced and more efficient methods for planting crops.

"If we can harness the power of genetics and determine what causes these copies of genes, we could produce plants that are more pest-resistant to insects that are co-evolving with them," Pires said.

"It could open different avenues for creating plants and food that are more efficiently grown."

The University of Missouri-led study is featured in the journal Proceedings of the National Academy of Sciences.

Photo: Liz West | Flickr