Female accessory glands of Adoxophyes honmai contain elicitor inducing tea leaves to arrest the egg-larval parasitoid, Ascogaster reticulata

Abstract

Plants exhibit various defense mechanisms against pathogens and herbivores, which are induced by pathogen/herbivore-derived elicitors. Ascogaster reticulata (Hymenoptera: Braconidae) is an egg-larval parasitoid of the smaller tea tortrix moth Adoxophyes honmai (Lepidoptera: Tortricidae), a serious pest moth of tea plants. In tea plants, egg deposition by A. honmai induces tea leaves to arrest A. reticulata. In a previous study, homogenate of the whole reproductive system from female moths showed elicitor activity that induced tea plant responses. The present study aimed to understand the elicitor-mediated interactions among the tea plant, A. honmai moth, and A. reticulata parasitoid to clarify the elicitor-secreting organs and characterize the elicitors. Investigation of elicitor activity that induced tea leaves to arrest parasitoids in leaves treated with homogenates of each organ of the reproductive system revealed the elicitor activity only in leaves treated with the homogenates of accessory glands, but not those of other organs. Furthermore, proteinase treatment of accessory gland homogenates resulted in loss of elicitor activity. These results suggest that elicitors derived from egg deposition by A. honmai, which induce tea leaves to arrest parasitoids, are proteinaceous compounds specifically contained in the accessory glands of female moths. Our findings contribute to identifying the elicitors and the application of biological control in tea fields.