The impacts of management practices on industrial hemp chemistry, physiology, and microbiome ecology.

Agroecology incorporates ecology and agronomy to inform crop management. Industrial hemp (Cannabis sativa L.) is a prime system to investigate agroecological questions because it has only recently been authorized for commercial cultivation and its sensitivity to biotic and abiotic stressors is unresolved. Here, I investigate how some conventional management choices, including the application of fungicide, plastic mulch, and irrigation, impact the physiology, chemistry, and microbial ecology of industrial hemp. Overall, I found that industrial hemp can be both resilient and resistant to these stressors, an important development for the industry. In Chapter II, I tested the impacts of fungicide application and fungal pathogen inoculation on the non-target leaf endophyte community. Fungal endophytes are ubiquitous plant symbionts and appreciated for their role in modulating stress response in plants, making them of interest for agroecological applications. Fungicide application not only reduced pathogen abundance but also altered fungal endophyte community composition. Chapter III investigated the impact of irrigation applied in a plastic mulch system on hemp chemistry, physiology, and endophyte community, and Chapter IV examined the effects of insufficient and excess vi water on hemp chemistry and physiology. In both chapters, I found that water availability did not cause changes in plant physiology and had only minor impacts on hemp chemistry. As part of developing agroecological solutions for hemp management, I also utilized hemp-isolated fungal endophytes to test their potential to mitigate impacts from insect predation and water stress. In Chapter II, I inoculated diet with a potentially entomopathogenic endophyte to test its effects on the larvae of a hemp pest and found that fungal inoculation had no negative impacts. In Chapter IV, I inoculated plants with two fungal endophytes to test if they modulated stress response to water availability. Endophyte inoculation only had minor effects on the concentration of two cannabinoids. While endophytes did not elicit the target effects, they still have potential to be implemented in management for other purposes, such as a biological control against microbial pathogens. This dissertation contributes to the growing knowledge of industrial hemp and can be used to inform future agroecological investigations in this emerging crop.