Sweet potatoes are becoming more and more popular globally: Whether in soup or as fries, they increasingly compete with "regular" potatoes to which, surprisingly, they are only distantly related. Although economically not as important as the potato world-wide, the sweet potato has a higher nutritional value and is richer in vitamins. This makes the crop is an important source of nutrients, particularly in Asia.
As with potatoes, there are different cultivars of sweet potatoes available, all displaying their own characteristics. Even cultivars grown in the field under similar conditions may differ strikingly with respect to insect attack. In previous studies, a cultivar known as Tainong 57 had demonstrably higher resistance to field herbivores in comparison to the cultivar known as Tainong 66. When attacked, the plants' leaves emit a distinct odor bouquet.
Researchers at the Max Planck Institute for Chemical Ecology in Jena, Germany, and at the National Taiwan University wanted to find out whether the high insect resistance in one cultivar was related to this odor. They especially wanted to know whether sweet potatoes have mechanisms to activate defense responses via volatile signals, as described in other plant species.
First the scientists examined what happens in a plant after it has been attacked by herbivores. Plants of the resistant cultivar synthesize a plant hormone in the wounded leaves that is important for activating defense mechanisms. These plants also emit a bouquet of odors.