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INTRASPECIES VARIATION IN MYCORRHIZAL RESPONSE OF MEDICAGO SATIVA TO RHIZOPHAGUS IRREGULARIS UNDER ABIOTIC STRESS

Date

2023-08-17

Journal Title

Journal ISSN

Volume Title

Publisher

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Type

Thesis

Degree Level

Masters

Abstract

Arbuscular mycorrhizal fungi are considered beneficial for their host plants, contributing to better growth, especially in stressful conditions. Actual plant outcomes can vary from beneficial to detrimental depending on both participant’s identity and the environmental context. Understanding plant-AMF symbiosis is a key component to understanding plant functioning. Additionally, there is potential for AMF use in developing sustainable agricultural practices. There are multiple methods that seek to explain the mechanisms behind variation in AMF symbiosis, and predict outcomes, such as using resource economics, or plant root morphology. While broad differences in AMF responsiveness between plant species can be explained these ways with varying success, intraspecific differences are not well understood. Our study aimed to target the context dependency and intraspecific variation of mycorrhizal relationships by using nine alfalfa cultivars (Medicago sativa) to determine how different cultivar attributes or trait expression might alter the plant-AMF, and plant-AMF-pollinator relationships in different stress contexts. We performed a greenhouse trial on alfalfa plants inoculated with Rhizophagus irregularis, exposing them to drought, salt, or low nutrient stress, to compare to alfalfa grown under unstressed conditions. We measured how bee visitation, flower number, seed production, biomass, N and P content changed with stress and AMF inoculation. We also measured how variation in specific root length, root tissue density, and root diameter interacted with mycorrhizal effects. Our study showed growth conditions mattered more for determining AMF affects on growth and stress response than cultivar identity did. Biomass and nutrient concentrations were fairly consistent across cultivars in each stress treatment group, and AMF had largely neutral or negative effects on biomass across treatments. AMF Increased biomass stress responses to drought and saline soil, marginally improved nutrient uptake, but did not ultimately determine plant seed production. AMF effects did not correlate with root trait expression. Plants attained sufficient nutrients without AMF, and it is likely that the negative affects seen in inoculated plants were a result of stressed AMF acting as a drain on resources. Our study highlights the context specificity of mycorrhizal interactions with plants, and the lack of understanding of the role fungi identity and origin plays in this relationship.

Description

Keywords

Mycorrhizal fungi, Alfalfa, Abiotic stress,

Citation

Degree

Master of Science (M.Sc.)

Department

Plant Sciences

Program

Plant Sciences

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DOI

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