Thesis Defence: Ecological strategy and differential effect among plants grown with conspecifics of Rhizophagus irregularis in the presence of a native soil microbial community

Max Brubaker, supervised by Dr. Miranda Hart, will defend their thesis titled “Ecological strategy and differential effect among plants grown with conspecifics of Rhizophagus irregularis in the presence of a native soil microbial community” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Max Brubaker’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.

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ABSTRACT

Arbuscular mycorrhizal fungi (AMF) are a group of root associating soil microorganisms that interact with most land plants and play key roles in the uptake of limiting nutrients. With increased need for biological fertilizers as an alternative option to chemical application, AMF have gained attention as microbial amendments in agricultural and remediation settings. However, the growth response of plants when grown with different isolates of the same AMF species (conspecifics) varies considerably and yet remains poorly understood. Furthermore, the extent to which different conspecifics impact plant response in the presence of native soil has received little attention. This study investigated how different grasses and forbs respond to the inoculation of two Rhizophagus irregularis conspecifics in the presence of a native soil consortium. In this study I use the term “differential effect” to help better understand the symbiotic response of different plant and fungal pairings (see 1.2). Given previous discussion on the alignment of functional strategy between partners I hypothesized that plants and AMF that expressed similar levels of ruderal traits would perform best together. I also hypothesized that an increase in soil nutrient status would best benefit plants and fungi with most ruderal traits. This study was conducted in a greenhouse at UBCO Plant-Facility where plant identity, AMF identity, and soil nutrients were manipulated. In general, I found no support for either of my hypotheses and only observed a few occurrences of differential effect. Additionally, I found that conspecifics of a highly commercialized species overall resulted in very low levels of colonization. This study highlights the potential importance of a native microbial community on the impact of how plants respond to the addition of a single AMF. With the numerous observations of differential effect in sterile conditions it is essential that we better understand the extent to which it occurs in the presence of a native soil consortium. Should differential effect be less prominent in the presence of a native soil or manifest only under certain conditions, this would be critical for the continued use of microbial amendments around the world.