Testing the efficacy of arbuscular mycorrhizal fungal inoculants on grapevine establishment

Arbuscular mycorrhizal (AM) fungi are often incorporated into growing systems in hopes of increasing nutrient uptake and alleviating stress for plants in exchange for photosynthetic carbon. However, the benefits provided by AM fungi are inconsistent and it is important we understand the factors surrounding this symbiosis to determine when their addition may be beneficial and economical for agricultural production systems. I used three greenhouse experiments and one field study to answer questions revolving around the timing of inoculation, the provenance of AM fungi used, and plant stresses. AM fungi did not consistently benefit plants, but some advantages were found. Overall, AM fungi were shown to be variable in their effect on vine growth. In a greenhouse study, a natural AM fungal community provided physiological benefits to hosts when compared to a commercial AM inoculant. In contrast, adding commercial AM fungi to grapevines prior to field transplant increased the survival of vines when entering stressful soil conditions. When testing the ability of AM fungi to protect young vines against a weak pathogen no benefits were observed, but instead AM fungi increased pathogen levels in hosts, though without any symptoms. Lastly, I tested how pruning of roots at the time of transplant may affect the symbiosis, finding that the symbiosis persisted likely due to the abundance of propagules in older, untrimmed roots. Thus, growers can pre-inoculate vines without compromising the symbiosis during planting. The range of results displayed in this thesis confirm how inconsistent AM fungal additions can be. Nevertheless, AM fungal inoculants may have a place in viticulture practices. In particular, they may be useful prior to transplanting into the field. In general, AM fungi should be tested on a site-basis prior to large scale applicationsArts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat