Early Development of Leaf Trichomes Is Associated With Decreased Damage in Teosinte, Compared With Maize, by Spodoptera frugiperda (Lepidoptera: Noctuidae)

Invertebrate herbivores prefer younger over older plant stages. Therefore, defensive traits against herbivores during early plant ontogeny are important. Defensive chemical and physical traits are well-studied in domesticated plants, but not in their wild relatives. Little is known about the function of trichomes, a physical defense against herbivore arthropods that damage cultivated plants and their wild ancestors. Maize is one of the most important crops in the world, but few studies have been conducted on the physical defenses during early ontogeny of maize and its wild relative teosinte. Therefore, the objective of this study was to characterize the density of trichomes (macrohairs) in maize and teosintes, and to evaluate the chewing damage by Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) larvae on the 6-leaf stage of 1) perennial teosinte Zea perennis (Poaceae), 2) annual teosinte Zea mays ssp. parviglumis, 3) landrace maize, and 4) on the 2-leaf stage of the landrace maize. Significantly less damage occurred in both teosinte species, which showed pubescence (trichomes) on the upper leaf-blade, but not on the midrib leaf surface. The highest trichome density was found on Z. perennis, followed by Z. mays ssp. parviglumis at the 6-leaf stage. No trichomes were found on the landrace maize, at the 6-leaf stage or 2-leaf stage. Results suggest that trichomes play an important role in preventing damage by chewing larvae on the ancestors of maize. Genes that promote macrohair initiation in teosintes during early vegetative development could be incorporated into maize plants in the future.