Variability in herbivore-induced odour emissions among maize cultivars andtheir wild ancestors (teosinte)

Maize plants respond to caterpillar feeding with the release of relatively large amounts of specific volatiles, which are known to serve as cues for p arasitoids to locate their host. Little is known about the genetic variabil ity in such herbivore-induced plant signals and about how the emissions in cultivated plants compare to those of their wild relatives. For this reason we compared the total quantity and the qualitative composition of the odou r blend among eleven maize cultivars and five wild Zen (Poaceae) species (t eosinte), as well as among the offspring of eight Zen mays mexicana plants from a single population. Young plants were induced to release volatiles by mechanically damaging the leaves and applying oral secretions of Spodopter a littoralis (Lepidoptera: Noctuidae) caterpillars to the wounded sites. Vo latiles were collected 7 h after treatment and subsequently analysed by gas chromatography. The total amounts of volatiles released were significantly different among maize cultivars as well as among the teosintes. Moreover, striking differences were found in the composition of the induced odour ble nds. Caryophyllene, for instance, was released by some, but not all varieti es and teosintes, and the ratios among monoterpenes and sesquiterpenes vari ed considerably. The offspring of different mother plants of the Z. m. mexi cana population showed some variation in the total amounts that they releas ed, but the composition of the odour blend was very consistent within the p opulation of this teosinte species. We discuss the ecological significance of these findings in terms of specificity and reliability of induced plant signals for parasitoids.