Kristen Guelly | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Kristen Guelly. This seminar is open to the general public to attend.

MSc with Dr. Boyd Mori. 

Thesis Topic: Exploring pheromone-based monitoring and chemosensory genes for the management of wheat midge, Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae)

Abstract: 

Wheat (Triticum aestivum L. (Poales: Poaceae)) is a staple crop providing a substantial portion of global human dietary protein and calorie intake. Wheat midge (Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae)) is a pest of economic importance in wheat crops in Eurasia and North America. Larval feeding causes significant damage to the developing wheat kernel, resulting in reductions to grain grade, quality, and yield. Sitodiplosis mosellana relies on the detection of host plant volatiles and conspecific pheromones through olfactory receptors for host plant selection and mating. Pheromone traps are essential tools for monitoring pest populations and guiding control measures, though their reliability in estimating populations for economic thresholds remains unclear. Chemosensory receptors involved in S. mosellana pheromone detection are poorly characterized, hindering the development of precise monitoring techniques. This project aimed to investigate S. mosellana monitoring strategies and their plant-host interactions. Specifically, two pheromone lure types (i.e., rubber septa and flex lures) and two trap types (i.e., Jackson and delta traps) were compared for their ability to capture S. mosellana males. Further, to understand the efficacy of pheromone traps as a monitoring tool, the number of males captured in pheromone traps was compared with emerging, overwintering, and ovipositing S. mosellana. Jackson traps baited with Trécé rubber septa lures captured the most midge in all sampling years, suggesting this is the most reliable combination for monitoring S. mosellana populations compared to delta traps. However, no reliable relationship was observed between male capture and overwintering, ovipositing, or emerging S. mosellana, indicating that pheromone traps may not accurately reflect female populations. Furthermore, this project aimed to identify chemosensory receptors to help characterize the function of specific olfactory receptors using a transcriptome-based approach. Sample collection and extraction were inadequate, which yielded low RNA concentrations and poor RNA sequencing, with no differential gene expression detected. Instead, a phylogenetic analysis of the annotated S. mosellana genome was conducted, comparing odorant receptors with those of Drosophila melanogaster Meigan (Diptera: Drosophilidae) and a related cecidomyid pest, Mayetiola destructor Say (Diptera: Cecidomyiidae). Several receptors responsible for mating and social behaviour in D. melanogaster and M. destructor were closely related to those in S. mosellana, suggesting their importance in pheromone detection. This work advances understanding of S. mosellana chemical ecology and its role in pest monitoring, offering potential for improved management of this economically significant pest.