9:00 am - 10:00 am
4-42 Earth Sciences Building, University of Alberta, Edmonton AB
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Aziz Ullah. This seminar is open to the general public to attend.
PhD with Dr. Nadir Erbilgin.
Thesis Topic: Understanding the Role of Secondary Metabolites and Endophytic Fungi in White Spruce Defenses Against Eastern Spruce Budworm
As a boreal tree species, white spruce (Picea glauca Moench Voss) is under a constant threat by outbreaks of defoliators (foliar feeders) including eastern spruce budworm (Choristoneura fumiferana). Historically, applications of biological insecticides and silvicultural tactics have been used to improve white spruce resistance or tolerance against the eastern spruce budworm. More recently, variations in chemical defenses, such as monoterpenes or phenolics, and fungal endophytes of white spruce have received a particular attention in forestry due to their potential roles in herbivory resistance. However, how such variations in white spruce defenses affect insect herbivores is largely unknown.
I sampled the foliage of 80 white spruce families and clustered them into two chemotypes (chemotypic phenotypes) based on their foliar monoterpene concentrations. I investigated the role of phenolics and monoterpenes in white spruce defense by observing how budworms respond to media amended with these metabolites. I found that the proportions and concentrations of monoterpenes and phenolics in the white spruce foliage negatively affected the survival of eastern spruce budworms. This study shows that different classes of defense metabolites are being coordinated against the same insect herbivore. In the follow up study, I characterized the composition of fungal endophytes and terpene defenses in the foliage of 30 white spruce genotypes in two locations. The fungal and terpene compositions varied across locations and genotypes. Intriguingly, genotypes with a higher terpene abundance also exhibited greater fungal abundance. I further tested the effects of selected endophytic fungi on spruce budworm performance and characterized their metabolite composition; these fungi contributed to budworm mortality, reduced weight, or attraction. In the final study, I grew seedlings from 30 different white spruce families (20 trees/family) from seeds in a growth chamber. After ten months of vegetative growth, I inoculated five fungal endophytes into the foliage’s of half of the seedlings in each family. The remaining half of the seedlings were not inoculated and set as the control treatment. After two months of inoculation, I harvested the seedlings, collected and weighed the above ground fresh biomass from both inoculated and control seedlings. Overall, the spruce families with higher endophytic fungal abundance also had higher monoterpene and sesquiterpene concentrations and foliage biomass.
In conclusion, these studies show how important monoterpenes, phenolics, and fungal endophytes are to white spruce’s defenses against herbivory. Monoterpenes contribute to toxicity, phenolics inhibit growth, and fungal endophytes change the host metabolites that make up defenses as well as contributing to budworm mortality.