Aziz Ullah | ALES Graduate Seminar

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 Aziz Ullah. This seminar is open to the general public to attend.

Thesis Topic: Chemotypic variations of lodgepole pine trees affect mountain pine beetle behaviour and growth of its symbiotic fungus

MSc with Dr. Nadir Erbilgin

Seminar Abstract:

Plants generally show large variations in their suitability to phytophagous insects and pathogens. Plant chemical defenses or secondary compounds are important components of plant resistance to pests. Lodgepole pine is one of the most abundant and widespread tree species in western Canada and shows various susceptibility to its primary enemy mountain pine beetle. During periodic outbreaks, mountain pine beetle can kill millions of pine trees and yet some individual trees survive from these outbreaks. Mechanisms driving the survival of these trees are not clear but are likely related to their chemical defenses. In this study, I utilized the natural variation in chemical defenses of lodgepole pine trees from progeny trials in northern Alberta and grouped them in four clusters (chemotypes) based on the composition of mainly monoterpene concentrations. I selected representative pine families in each cluster and used their chemical profiles in bioassays. My goal was to determine if lodgepole pine chemotypes differentially affect performance of mountain pine beetles and its fungal symbiont Grosmannia clavigera. I conducted two bioassays to assess the impact of chemotypes on the performance of mountain pine beetle and G. clavigera. For the beetle assays, I used a diet consisted of phloem and sapwood, mixed with agar and water. For G. clavigera, I prepared malt extract agar. In each bioassay, I either placed adult beetles or inoculated fungus on artificial diet amended with the monoterpene concentrations representing each of four pine clusters or 11 lodgepole pine families. I measured beetle egg gallery length and weight change as a proxy to host selection by beetles as well as fungal growth as proxy to fungal responses to host chemistry. I found a significant effect of chemotypes on beetle egg gallery length and weight change. Three pine families were least suitable for beetle performance and two families were least suitable for the fungal growth. The families which showed least suitability for beetle host acceptance had higher concentrations of limonene, γ-terpinene, 4-allylanisole, β-pinene, terpinolene, and cymene. The families with lowest fungal growth had higher concentrations of α-pinene, 3-carene, camphene, myrcene, γ-terpinene, bornyl acetate, borneol, and total monoterpenes. Overall, this study is the first to demonstrate how host phytochemistry differentially affects a bark beetle and its fungal symbiont. Furthermore, it reveals that performance of both mountain pine beetle and its fungal symbiont can be strongly influenced by host chemotypes. Pine families which showed least suitability for both beetles and its symbionts can be potentially used in restoration of mountain pine beetle impacted forests in Alberta to promote beetle-resistant forests.