A MULTI-PRONGED STUDY OF CRUCIFEROUS VEGETABLE CROP DEFENSES AGAINST AN EMERGENT GALL INSECT PEST

The invasive swede midge (Contarinia nasturtii, Diptera: Cecidomyiidae) is a destructive galling parasite of cruciferous crops (Brassica spp.) that attacks meristematic tissue and distorts growth. Feeding from a single swede midge larva can render an entire plant unmarketable. Management success remains elusive and host defenses against the swede midge are poorly understood. Novel approaches are necessary to control this pest.My major goal is to understand the mechanisms of Brassicavegetable host resistance to swede midge in order to open a new frontier for controlling this pest. This research aims to create new knowledge about gall insect pests and how they affect host crops, which could be applied in the future to major cropssuch as wheat, soybean, and grape.I will leverage my experience in molecular plant-insect dynamics to answer important questions about Brassica crops' defense against swede midge. Employing what I've developed in a model galling system, I propose transcriptomic, chemical, and morphological analyses across three objectives:(1) Identify key differences in two broccoli cultivars' defense against swede midge. This objective will establish a baseline for molecular host-parasite interaction in this crop system and illustrate how a single-heading broccoli variety defends itself compared to a branchingheirloom variety.(2) Subject a suite of Brassica crops and wild relatives to a swede midge feeding assay to identify candidate resistance-related genes. Based on extension research, there is an approximatespectrum of preference for swede midge when choosing a host; this experiment will comparatively analyze various Brassica varieties to determine what genotypes and phenotypes contribute to resistance or susceptibility to swede midge infestation.(3) Use a promising non-transgenic technique to transiently augment host resistance and identify how the swede midge defeats host defenses on a molecular level. This objective will innovatively manipulate Brassica crops' gene expression with RNAi, a technique that has seen success and federal approval in products for managing insect pests; I will transiently increase or decrease native host plant defenses to create windows of susceptibility or resistance and characterize how such defenses deter the swede midge.